XX. ECHINODERMATA[217]
[217] The following classification of the Echinodermata is employed in this chapter: I. Holothuroidea. II. Asteroidea. III. Ophiuroidea. IV. Echinoidea. V. Crinoidea.
The development of the Echinodermata naturally falls into two sections:--
(1) The development of the germinal layers and of the systems of organs; (2) the development of the larval appendages and the metamorphosis.
The Development of the Germinal Layers and of the Systems of Organs.
The development of the systems of organs presents no very important variations within the limits of the group.
Holothuroidea. The Holothurians have been most fully studied (Selenka, No. 563), and may be conveniently taken as type.
The segmentation is nearly regular, though towards its close, and in some instances still earlier, a difference becomes apparent between the upper and the lower poles.
At the close of segmentation (fig. 247 A) the egg has a nearly spherical form, and is constituted of a single layer of columnar cells enclosing a small segmentation cavity. The lower pole is slightly thickened, and the egg rotates by means of fine cilia.
An invagination now makes its appearance at the lower pole (fig. 247 B), and simultaneously there become budded off from the cells undergoing the invagination amoeboid cells, which eventually form the muscular system and the connective tissue. These cells very probably have a bilaterally symmetrical origin. This stage represents the gastrula stage which is common to all Echinoderms. The invaginated sack is the archenteron. As it grows larger one side of the embryo becomes flattened, and the other more convex. On the flattened side a fresh invagination arises, the opening of which forms the permanent mouth, the opening of the first invagination remaining as the permanent anus (fig. 248 A).
[FIG. 247. TWO STAGES IN THE DEVELOPMENT OF HOLOTHURIA TUBULOSA VIEWED IN OPTICAL SECTION. (After Selenka.)
A. Blastosphere stage at the close of segmentation. B. Gastrula stage. mr. micropyle; fl. chorion; s.c. segmentation cavity; bl. blastoderm; ep. epiblast; hy. hypoblast; ms. amoeboid cells derived from hypoblast; a.e. archenteron.]
These changes give us the means of attaching definite names to the various parts of the embryo. It deserves to be noted in the first place that the embryo has assumed a distinctly bilateral form. There is present a more or less concave surface extending from the mouth to near the anus, which will be spoken of as the ventral surface. The anus is situated at the posterior extremity. The convex surface opposite the ventral surface forms the dorsal surface, which terminates anteriorly in a rounded præ-oral prominence.
It will be noticed in fig. 248 A that in addition to the primitive anal invagination there is present a vesicle (v.p.). This vesicle is directly formed by a constriction of the primitive archenteron (fig. 249 Vpv.), and is called by Selenka the vaso-peritoneal vesicle. It gives origin to the epithelioid lining of the body cavity and water-vascular system of the adult[218]. In the parts now developed we have the rudiments of all the adult organs.
[218] The origin of the vaso-peritoneal vesicle is not quite the same in all the species. In Holothuria tubulosa it is separated from the cæcal end of the archenteron; the remainder of which then grows towards the oral invagination. In Cucumaria the archenteron forks (fig. 249); and one fork forms the vaso-peritoneal vesicle, and the other the major part of the mesenteron.
The mouth and anal involutions (after the separation of the vaso-peritoneal vesicle) meet and unite, a constriction indicating their point of junction (fig. 248 B). Eventually the former gives rise to the mouth and oesophagus, and the latter to the remainder of the alimentary canal[219].
[219] There appears to be some uncertainty as to how much of the larval oesophagus is derived from the stomodæal invagination.
[FIG. 248. THREE STAGES IN THE DEVELOPMENT OF HOLOTHURIA TUBULOSA VIEWED FROM THE SIDE IN OPTICAL SECTION. (After Selenka.)
m. mouth; oe. oesophagus; st. stomach; i. intestine; a anus; l.c. longitudinal ciliated band; v.p. vaso-peritoneal vesicle; p.v. peritoneal vesicle; p.r. right peritoneal vesicle; pl. left peritoneal vesicle; w.v. water-vascular vesicle; p. dorsal pore of water-vascular system; ms. muscle cells.]
The vaso-peritoneal vesicle undergoes a series of remarkable changes. After its separation from the archenteron it takes up a position on the left side of this, elongates in an antero-posterior direction, and from about its middle sends a narrow diverticulum towards the dorsal surface of the body, where an opening to the exterior becomes formed (fig. 248 B, p.). The diverticulum becomes the madreporic canal, and the opening the dorsal pore.
The vaso-peritoneal vesicle next divides into two, an anterior vesicle (fig. 248 B, w.v.), from which is derived the epithelium of the water-vascular system, and a posterior (fig. 248 B, p.v.), which gives rise to the epithelioid lining of the body cavity. The anterior vesicle (fig. 248 C, w.v.) becomes five-lobed, takes a horseshoe-shaped form, and grows round the oesophagus (fig. 256, w.v.r). The five lobes form the rudiments of the water-vascular prolongations into the tentacles. The remaining parts of the water-vascular system are also developed as outgrowths of the original vesicle. Five of these, alternating with the original diverticula, form the five ambulacral canals, from which diverticula are produced into the ambulacral feet; a sixth gives rise to the Polian vesicle. The remaining parts of the original vesicle form the water-vascular ring.
We must suppose that eventually the madreporic canal loses its connection with the exterior so as to hang loosely in the interior, though the steps of this process do not appear to have been made out.
[FIG. 249. LONGITUDINAL SECTION THROUGH AN EMBRYO OF CUCUMARIA DOLIOLUM AT THE END OF THE FOURTH DAY.
Vpv. vaso-peritoneal vesicle; ME. mesenteron; Blp., Ptd. blastopore, proctodæum.]
The original hinder peritoneal vesicle grows rapidly, and divides into two (fig. 248 C, pl. and pr.), which encircle the two sides of the alimentary canal, and meet above and below it. The outer wall of each of them attaches itself to the skin, and the inner one to the alimentary canal and water-vascular system; in both cases the walls remain separated from the adjacent parts by a layer of the amoeboid cells already spoken of. The cavity of the peritoneal vesicles becomes the permanent body cavity. Where the walls of the two vesicles meet on the dorsal side, a mesentery, suspending the alimentary canal and dividing the body cavity longitudinally, is often formed. In other parts the partition walls between the two sacks appear to be absorbed.
The amoeboid cells, which were derived from the invaginated cells, arrange themselves as a layer round all the organs (fig. 249). Some of them remain amoeboid, attach themselves to the skin, and form part of the cutis; and in these cells the calcareous spicula of the larva and adult are formed. Others form the musculature of the larval alimentary tract, while the remainder give rise to the musculature and connective tissue of the adult.
The development of the vascular system is not known, but the discovery of Kowalevsky, confirmed by Selenka, that from the walls of the water-vascular system corpuscles are developed, identical with those in the blood-vessels, indicates that it probably develops in connection with the water-vascular system. The observations of Hoffmann and Perrier on the communication of the two systems in the Echinoidea point to the same conclusion. Though nothing very definite is known with reference to the development of the nervous system, Metschnikoff suggests that it develops in connection with the thickened bands of epiblast which are formed by a metamorphosis of the ciliated bands of the embryo, and accompany the five radial tubes (vide p. 555). In any case its condition in the adult leaves no doubt of its being a derivative of the epiblast.
From the above description the following general conclusions may be drawn:--
(1) The blastosphere stage is followed by a gastrula stage.
(2) The gastrula opening forms the permanent anus, and the mouth is formed by a fresh invagination.
(3) The mesoblast arises entirely from the invaginated cells, but in two ways:--
(a) As scattered amoeboid cells, which give origin to the muscles and connective tissue (including the cutis) of the body wall and alimentary tract.
(b) As a portion separated off from the archenteron, which gives rise both to the epithelioid lining of the body cavity, and of the water-vascular system.
(4) The oesophagus is derived from an invagination of the epiblast, and the remainder of the alimentary canal from the archenteron.
(5) The embryonic systems of organs pass directly into those of the adult.
The development of Synapta diverges, as might be expected, to a very small extent from that of Holothuria.
Asteroidea. In Asterias the early stages of development conform to our type. There arise, however, two bilaterally symmetrical vaso-peritoneal diverticula from the archenteron. These diverticula give rise both to the lining of the body cavity and water-vascular system. With reference to the exact changes they undergo there is, however, some difference of opinion. Agassiz (543) maintains that both vesicles are concerned in the formation of the water-vascular system, while Metschnikoff (560) holds that the water-vascular system is entirely derived from the anterior part of the larger left vesicle, while the right and remainder of the left vesicle form the body cavity. Metschnikoff's statements appear to be the most probable. The anterior part of the left vesicle, after separating from the posterior, grows into a five-lobed rosette (fig. 260, i), and a madreporic canal (h) with a dorsal pore opening to the exterior. The rosette appears not to grow round the oesophagus, as in the cases hitherto described. But the latter is stated to disappear, and a new oesophagus to be formed, which pierces the rosette, and places the old mouth in communication with the stomach. Except where the anus is absent in the adult, the larval anus probably persists.
Ophiuroidea. The early development of the Ophiuroidea is not so fully known as that of other types. Most species have a free-swimming larva, but some (Amphiura) are viviparous.
The early stages of the free-swimming larvæ have not been described, but I have myself observed in the case of Ophiothrix fragilis that the segmentation is uniform, and is followed by the normal invagination. The opening of this no doubt remains as the larval anus, and there are probably two outgrowths from this to form the vaso-peritoneal vesicles. Each of these divides into two parts, an anterior lying close to the oesophagus, and a posterior close to the stomach. The anterior on the right side aborts; that on the left side becomes the water-vascular vesicle, early opens to the exterior, and eventually grows round the oesophagus, which, as in Holothurians, becomes the oesophagus of the adult. The posterior vesicles give rise to the lining of the body cavity, but are stated by Metschnikoff to be at first solid, and only subsequently to acquire a cavity--the permanent body cavity. The anus naturally disappears, since it is absent in the adult. In the viviparous type the first stages are imperfectly known, but it appears that the blastopore vanishes before the appearance of the mouth. The development of the vaso-peritoneal bodies takes place as in the free-swimming larvæ.
Echinoidea. In the Echinoidea (Agassiz, No. 542, Selenka, No. 564) there is a regular segmentation and the normal invagination (fig. 250 A). The amoeboid mesoblast cells arise as two laterally placed masses, and give rise to the usual parts. The archenteron grows forward and bends towards the ventral side (fig. 250 B). It becomes (fig. 250 C) divided into three chambers, of which the two hindermost (d and c) form the stomach and intestine; while the anterior forms the oesophagus, and gives rise to the vaso-peritoneal vesicles. These latter appear as a pair of outgrowths (fig. 251), but become constricted off as a single two-horned vesicle, which subsequently divides into two. The left of these is eventually divided, as in Asteroids, into a peritoneal and water-vascular sack, while the right forms the right peritoneal sack. An oral invagination on the flattened ventral side meets the mesenteron after its separation from the vaso-peritoneal vesicle. The larval anus persists, as also does the larval mouth, but owing to the manner in which the water-vascular rosette is established the larval oesophagus appears to be absorbed, and to be replaced by a fresh oesophagus.
[FIG. 250. THREE SIDE VIEWS OF EARLY STAGES IN THE DEVELOPMENT OF STRONGYLOCENTRUS. (From Agassiz.)
a. anus (blastopore); d. stomach; o. oesophagus; c. rectum; w. vaso-peritoneal vesicle; v. ciliated ridge; r. calcareous rod.]
Crinoidea. Antedon, the only Crinoid so far studied (Götte, No. 549), presents some not inconsiderable variations from the usual Echinoderm type. The blastopore is placed on the somewhat flattened side of the oval blastosphere, and not, as is usual, at the hinder end.
[FIG. 251. DORSO-VENTRAL VIEW OF AN EARLY LARVA OF STRONGYLOCENTRUS. (From Agassiz.)
a. anus; d. stomach; o. oesophagus; w. vaso-peritoneal vesicle; r. calcareous rod.]
The blastopore completely closes, and is not converted into the permanent anus. The archenteron gives rise to the epithelioid lining of both body cavity and water-vascular system. These parts do not, however, appear as a single or paired outgrowth from the archenteron, but as three distinct outgrowths which are not formed contemporaneously. Two of them are first formed, and become the future body cavity; but their lumens remain distinct. Originally appearing as lateral outgrowths, the right one assumes a dorsal position and sends a prolongation into the stalk (fig. 252, rp´), and the left one assumes first a ventral, and then an oral position (fig. 252, lp).
[FIG. 252. LONGITUDINAL SECTION THROUGH AN ANTEDON LARVA. (From Carpenter; after Götte.)
al. mesenteron; wv. water-vascular ring; lp. left (oral) peritoneal vesicle; rp. right peritoneal vesicle; rp´. continuation of right vesicle into the stalk; st. stalk.]
The third outgrowth of the archenteron gives rise to the water-vascular vesicle. It first grows round the region of the future oesophagus and so forms the water-vascular ring. The wall of the ring then grows towards the body wall so as to divide the oral (left) peritoneal vesicle into two distinct vesicles, an anterior and a posterior, shewn in fig. 253, lp´ and lp. Before this division is completed, the water-vascular ring is produced in front into five processes--the future tentacles (fig. 252, wv)--which project into the cavity of the oral vesicle (lp). After the oral peritoneal space has become completely divided into two parts, the anterior dilates (fig. 253, lp´) greatly, and forms a large vestibule at the anterior end of the body. This vestibule (lp´) next acquires a communication with the mesenteron, shewn in fig. 253 at m. The anterior wall of this vestibule is finally broken through. By this rupture the mesenteron is placed in communication with the exterior by the opening at m, while at the same time the tentacles of the water-vascular ring (t) project freely to the exterior. Such is Götte's account of the præ-oral body space, but, as he himself points out, it involves our believing that the lining of the diverticulum derived from the primitive alimentary vesicle becomes part of the external skin. This occurrence is so remarkable, that more evidence appears to me requisite before accepting it.
The formation of the anus occurs late. Its position appears to be the same as that of the blastopore, and is indicated by a papilla of the mesenteron attaching itself to the skin on the ventral side (fig. 253, an). It eventually becomes placed in an interradial space within the oral disc of the adult. The water-vascular ring has no direct communication with the exterior, but the place of the madreporic canal of other types appears to be taken in the larva by a single tube leading from the exterior into the body cavity, the external opening of which is placed on one of the oral plates (vide p. 571) in the next interradial space to the right of the anus, and a corresponding diverticulum of the water-vascular ring opening into the body cavity. The line of junction between the left and right peritoneal vesicles forms in the larva a ring-like mesentery dividing the oral from the aboral part of the body cavity. In the adult[220] the oral section of the larval body cavity becomes the ventral part of the circumvisceral division of the body cavity, and the subtentacular canals of the arms and disc; while the aboral section becomes the dorsal part of the circumvisceral division of the body cavity, the coeliac canals of the arms, and the cavity of the centro-dorsal piece. The primitive distinction between the sections of the larval body cavity becomes to a large extent obliterated, while the axial and intervisceral sections of the body cavity of the adult are late developments.
[220] Vide P. H. Carpenter, "On the genus Actinometra." Linnean Trans., 2nd Series, Zoology, Vol. II., Part I., 1879.
[FIG. 253. LONGITUDINAL SECTION THROUGH THE CALYX OF AN ADVANCED PENTACRINOID ANTEDON LARVA WITH CLOSED VESTIBULE. (From Carpenter; after Götte.)
ae. epithelium of oral vestibule; m. mouth; al. mesenteron; an. rudiment of permanent anus; lp. posterior part of left (oral) peritoneal sack; lp´. anterior part of left (oral) peritoneal sack; wr. water-vascular ring; t. tentacle; mt. mesentery; rp. right peritoneal sack; rp´. continuation of right peritoneal sack into the stalk; r. roof of tentacular vestibule.]
The more important points in the development indicated in the preceding pages are as follows:
(1) The blastosphere is usually elongated in the direction of the axis of invagination, but in Comatula it is elongated transversely to this axis.
(2) The blastopore usually becomes the permanent anus, but it closes at the end of larval life (there being no anus in the adult) in Ophiuroids and some Asteroids, while in Comatula it closes very early, and a fresh anus is formed at the point where the blastopore was placed.
(3) The larval mouth always becomes the mouth of the adult.
(4) The archenteron always gives rise to outgrowths which form the peritoneal membrane and water-vascular systems. In Comatula there are three such outgrowths, two paired, which form the peritoneal vesicles, and one unpaired, which forms the water-vascular vesicle. In Asteroids and Ophiuroids there are two outgrowths. In Ophiuroids both of these are divided into a peritoneal and a water-vascular vesicle, but the right water-vascular vesicle atrophies. In Asteroids only one water-vascular vesicle is formed, which is derived from the left peritoneal vesicle. In Echinoids and Holothuroids there is a single vaso-peritoneal vesicle.
(5) The water-vascular vesicle grows round the larval oesophagus in Holothuroids, Ophiuroids, and Comatula; in these cases the larval oesophagus is carried on into the adult. In other forms the water-vascular vesicle forms a ring which does not enclose the oesophagus (Asteroids and Echinoids); in such cases a new oesophagus is formed, which perforates this ring.
Development of the larval appendages and metamorphosis.
Holothuroidea. The young larva of Synapta, to which J. Müller gave the name Auricularia (fig. 255), is in many respects the simplest form of Echinoderm larva. With a few exceptions the Auricularia type of larva is common to the Holothuria.
[FIG. 254. A. THE LARVA OF A HOLOTHUROID. B. THE LARVA OF AN ASTEROID.
m. mouth; st. stomach; a. anus; l.c. primitive longitudinal ciliated band; pr.c. præ-oral ciliated band.]
It is (fig. 254 A and fig. 255) bilaterally symmetrical, presenting a flattened ventral surface, and a convex dorsal one. The anus (an) is situated nearly at the hinder pole, and the mouth (m) about the middle of the ventral surface. In front of the mouth is a considerable process, the præ-oral lobe. Between the mouth and anus is a space, more or less concave according to the age of the embryo, interrupted by a ciliated ridge a little in front of the anus. A similar ciliated ridge is present on the ventral surface of the præ-oral lobe immediately in front of the mouth. The anal and oral ridges are connected by two lateral ciliated bands, the whole forming a continuous band, which, since the mouth lies in the centre of it (fig. 255), may be regarded as a ring completely surrounding the body behind the mouth, or more naturally as a longitudinal ring.
[FIG. 255. DIAGRAMMATIC FIGURES REPRESENTING THE EVOLUTION OF AN AURICULARIA FROM THE SIMPLEST ECHINODERM LARVAL FORM. (Copied from Müller.)
The black line represents the ciliated ridge. The shaded part is the oral side of the ring, the clear part the aboral side. m. mouth; an. anus.]
The bilateral Auricularia is developed from a slightly elongated gastrula with an uniform covering of cilia. The gastrula becomes flattened on the oral side. At the same time the cilia become specially developed on the oral and anal ridges, and then on the remainder of the ciliated ring, while they are simultaneously obliterated elsewhere; and so a complete Auricularia is developed. The water-vascular ring in the fully developed larva has already considerably advanced in the growth round the oesophagus (fig. 256 w.v.r).
Most Holothurian larvæ, in their transformation from the bilateral Auricularia form to the radial form of the adult, pass through a stage in which the cilia form a number of transverse rings, usually five in number, surrounding the body. The stages in this metamorphosis are shewn in figs. 256, 257, and 258.
[FIG. 256. FULL-GROWN LARVA OF SYNAPTA. (After Metschnikoff.)
m. mouth; st. stomach; a. anus; p.v. left division of perivisceral cavity, which is still connected with the water-vascular system; w.v.r. water-vascular ring which has not yet completely encircled the oesophagus; l.c. longitudinal part of ciliated band; pr.c. præ-oral part of ciliated band.]
The primitive ciliated band, at a certain stage of the metamorphosis, breaks up into a number of separate portions (fig. 256), the whole of which are placed on the ventral surface. Four of these (fig. 257 A and B) arrange themselves in the form of an angular ring round the mouth, which at this period projects considerably. The remaining portions of the primitive band change their direction from a longitudinal one to a transverse (fig. 257 B), and eventually grow into complete rings (fig. 257 C). Of these there are five. The middle one (257 B) is the first to develop, and is formed from the dorsal parts of the primitive ring. The two hinder rings develop next, and last of all the two anterior ones, one of which appears to be in front of the mouth (fig. 257 C).
[FIG. 257. THREE STAGES IN THE DEVELOPMENT OF SYNAPTA. A and B are viewed from the ventral surface, and C from the side. (After Metschnikoff.)
m. mouth; oe. oesophagus; pv. walls of the perivisceral cavity; wv. longitudinal vessel of the water-vascular system; p. dorsal pore of water-vascular system; cr. ciliated ring formed round the mouth from parts of the primitive ciliated band.]
The later development of the mouth, and of the ciliated ridge surrounding it, is involved in some obscurity. It appears from Metschnikoff (No. 560) that an invagination of the oesophagus takes place, carrying with it the ciliated ridge around the mouth. This ridge becomes eventually converted into the covering for the five tentacular outgrowths of the water-vascular ring (fig. 258), and possibly also forms the nervous system.
The opening of the oesophageal invagination is at first behind the foremost ciliated ring, but eventually comes to lie in front of it, and assumes a nearly terminal though slightly ventral position (fig. 258). No account has been given of the process by which this takes place, but the mouth is stated by Metschnikoff (though Müller differs from him on this point) to remain open throughout. The further changes in the metamorphosis are not considerable. The ciliated bands disappear, and a calcareous ring of ten pieces, five ambulacral and five interambulacral, is formed round the oesophagus. A provisional calcareous skeleton is also developed.
[FIG. 258. A LATE STAGE IN THE DEVELOPMENT OF SYNAPTA. (After Metschnikoff.)
The figure shews the vestibular cavity with retracted tentacles; the ciliated bands; the water-vascular system, etc. p. dorsal pore of water-vascular system; pv. walls of perivisceral cavity; ms. amoeboid cells.]
All the embryonic systems of organs pass in this case directly into those of the adult.
The metamorphosis of most Holothuroidea is similar to that just described. In Cucumaria (Selenka) there is however no Auricularia stage, and the uniformly ciliated stage is succeeded by one with five transverse bands of cilia, and a præ-oral and an anal ciliated cap. The mouth is at first situated ventrally behind the præ-oral cap of cilia, but the præ-oral cap becomes gradually absorbed, and the mouth assumes a terminal position.
In Psolinus (Kowalevsky) there is no embryonic ciliated stage, and the adult condition is attained without even a metamorphosis. There appear to be five plates surrounding the mouth, which are developed before any other part of the skeleton, and are regarded by P. H. Carpenter (No. 548) as equivalent to the five oral plates of the Crinoidea. The larval condition with ciliated bands is often spoken of as the pupa stage, and during it the larvæ of Holothurians proper use their embryonic tube feet to creep about.
Asteroidea. The commonest and most thoroughly investigated form of Asteroid larva is a free-swimming form known as Bipinnaria.
This form in passing from the spherical to the bilateral condition passes through at first almost identical changes to the Auricularian larva. The cilia become at an early period confined to an oral and anal ridge.
The anal ridge gradually extends dorsalwards, and finally forms a complete longitudinal post-oral ring (fig. 259 A); the oral ridge also extends dorsalwards, and forms a closed præ-oral ring (fig. 259 A), the space within which is left unshaded in my figure.
The presence of two rings instead of one distinguishes the Bipinnaria from the Auricularia. The two larvæ are shewn side by side in fig. 254, and it is obvious that the two bands of the Bipinnaria are (as pointed out by Gegenbaur) equivalent to the single band of the Auricularia divided into two. Ontologically, however, the two bands of Bipinnaria do not appear to arise from the division of a single band.
As the Bipinnaria grows older, a series of arms grows out along lines of the two ciliated bands (fig. 259 C), and, in many cases, three special arms are formed, not connected with the ciliated bands, and covered with warts. These latter arms are known as brachiolar arms, and the larvæ provided with them as Brachiolaria (fig. 259 D).
[FIG. 259. DIAGRAMMATIC REPRESENTATION OF VARIOUS FORMS OF ASTEROID LARVÆ. A, B, C, BIPINNARIA; D, BRACHIOLARIA. (Copied from Müller.)
The black lines represent the ciliated bands; and the shading the space between the præ-oral and the post-oral bands. m. mouth; an. anus.]
As a rule the following arms can be distinguished (fig. 259 C and D), on the hinder ring (Agassiz' nomenclature) a median anal pair, a dorsal anal pair, and a ventral anal pair, a dorsal oral pair, and an unpaired anterior dorsal arm; on the præ-oral ring a ventral oral pair, and sometimes (Müller) an unpaired anterior ventral arm.
The three brachiolar arms arise as processes from the base of the unpaired dorsal arm, and the two ventral oral arms. The extent of the development of the arms varies with the species.
The changes by which the Bipinnaria or Brachiolaria becomes converted into the adult starfish are very much more complicated than those which take place in Holothurians. For an accurate knowledge of them we are largely indebted to Alex. Agassiz (No. 543). The development of the starfish takes place entirely at the posterior end of the larva close to the stomach.
On the right and dorsal side of the stomach, and externally to the right peritoneal space, are formed five radially situated calcareous rods arranged in the form of a somewhat irregular pentagon. The surface on which they are deposited has a spiral form, and constitutes together with its calcareous rods, the abactinal or dorsal surface of the future starfish. Close to its dorsal, i.e. embryonic dorsal, edge lies the dorsal pore of the water-vascular system (madreporic canal), and close to its ventral edge the anus. On the left and ventral side of the stomach is placed the water-vascular rosette, the development of which was described on p. 549. It is situated on the actinal or ventral surface of the future starfish, and is related to the left peritoneal vesicle.
Metschnikoff (No. 560) and Agassiz (No. 543) differ slightly as to the constitution of the water-vascular rosette. The former describes and figures it as a completely closed rosette, the latter states that 'it does not form a completely closed curve but is always open, forming a sort of twisted crescent-shaped arc.'
The water-vascular rosette is provided with five lobes, corresponding to which are folds in the larval skin, and each lobe corresponds to one of the calcareous plates developed on the abactinal disc. The plane of the actinal surface at first meets that of the abactinal at an acute or nearly right angle. The two surfaces are separated by the whole width of the stomach. The general appearance of the larva from the ventral surface after the development of the water-vascular rosette (i) and abactinal disc (A) is shewn in fig. 260.
[FIG. 260. BIPINNARIA LARVA OF AN ASTEROID. (From Gegenbaur; after Müller.)
b. mouth; a. anus; h. madreporic canal; i. ambulacral rosette; c. stomach; d. g. e. etc. arms of Bipinnaria; A. abactinal disc of young Asteroid.]
As development proceeds the abactinal surface becomes a firm and definite disc, owing to the growth of the original calcareous spicules into more or less definite plates, and to the development of five fresh plates nearer the centre of the disc and interradial in position. Still later a central calcareous plate appears on the abactinal surface, which is thus formed of a central plate, surrounded by a ring of five interradial plates, and then again by a ring of five radial plates. The abactinal disc now also grows out into five short processes, separated by five shallow notches. These processes are the rudiments of the five arms, and each of them corresponds to one of the lobes of the water-vascular rosette. A calcareous deposit is formed round the opening of the water-vascular canal, which becomes the madreporic tubercle[221]. At about this stage the absorption of the larval appendages takes place. The whole anterior part of the larva with the great præ-oral lobe has hitherto remained unchanged, but now it contracts and undergoes absorption, and becomes completely withdrawn into the disc of the future starfish. The larval mouth is transported into the centre of the actinal disc. In the larvæ observed by Agassiz and Metschnikoff nothing was cast off, but the whole absorbed.
[221] The exact position of the madreporic tubercle in relation to the abactinal plates does not seem to have been made out. It might have been anticipated that it would be placed in one of the primary interradial plates, but this does not seem to be the case. The position of the anus is also obscure.
According to Müller and Koren and Danielssen this is not the case in the larva observed by them, but part of the larva is thrown off, and lives for some time independently.
After the absorption of the larval appendages the actinal and abactinal surfaces of the young starfish approach each other, owing to the flattening of the stomach; at the same time they lose their spiral form, and become flat discs, which fit each other. Each of the lobes of the rosette of the water-vascular system becomes one of the radial water-vascular canals. It first becomes five-lobed, each lobe forming a rudimentary tube foot, and on each side of the middle lobe two fresh ones next spring out, and so on in succession. The terminal median lobe forms the tentacle at the end of the arm, and the eye is developed at its base. The growth of the water-vascular canals keeps pace with that of the arms, and the tube feet become supported at their base by an ingrowth of calcareous matter. The whole of the calcareous skeleton of the larva passes directly into that of the adult, and spines are very soon formed on the plates of the abactinal surface. The original radial plates, together with the spines which they have, are gradually pushed outwards with the growth of the arms by the continual addition of fresh rows of spines between the terminal plate and the plate next to it. It thus comes about that the original radial plates persist at the end of the arms, in connection with the unpaired tentacles which form the apex of the radial water-vascular tubes.
It has already been mentioned that according to Metschnikoff (No. 560) a new oesophagus is formed which perforates the water-vascular ring, and connects the original stomach with the original mouth. Agassiz (No. 543) maintains that the water-vascular ring grows round the primitive oesophagus. He says--"During the shrinking of the larva the long oesophagus becomes shortened and contracted, bringing the opening of the mouth of the larva to the level of the opening of the oesophagus, which eventually becomes the true mouth of the starfish." The primitive anus is believed by Metschnikoff to disappear, but by Agassiz to remain. This discrepancy very possibly depends upon these investigators having worked at different species.
There is no doubt that the whole of the larval organs, with the possible exception of the oesophagus, and anus (where absent in the adult), pass directly into the corresponding organs of the starfish--and that the præ-oral part of the body and arms of the larva are absorbed and not cast off.
In addition to the Bipinnarian type of Asteroid larva a series of other forms has been described by Müller (No. 561), Sars, Koren, and Danielssen (No. 554) and other investigators, which are however very imperfectly known. The best known form is one first of all discovered by Sars in Echinaster Sarsii, and the more or less similar larvæ subsequently investigated by Agassiz, Busch, Müller, Wyville Thomson, etc. of another species of Echinaster and of Asteracanthion. These larvæ on leaving the egg have an oval form, and are uniformly covered by cilia. Four processes (or in Agassiz' type one process) grow out from the body; by these the larvæ fix themselves. In the case of Echinaster the larvæ are fixed in the ventral concavity of the disc of the mother, between the five arms, where a temporary brood-pouch is established. The main part of the body is converted directly into the disc of the young starfish, while the four processes come to spring from the ventral surface, and are attached to the water-vascular ring. Eventually they atrophy completely. Of the internal structure but little is known; till the permanent mouth is formed, after the development of the young starfish is pretty well advanced, the stomach has no communication with the exterior.
A second abnormal type of development is presented by the embryo of Pteraster miliaris, as described by Koren and Danielssen[222]. The larvæ to the number of eight to twenty develop in a peculiar pouch on the dorsal surface of the body. The early stages are not known, but in the later ones the whole body assumes a pentagonal appearance with a mouth at one edge of the disc. At a later stage the anus is formed on the dorsal side of an arm opposite the mouth. The stomach is surrounded by a water-vascular ring, from which the madreporic canal passes to the dorsal surface, but does not open. At a later stage the embryonic mouth and anus vanish, to be replaced by a permanent mouth and anus in the normal positions.
[222] The following statements are taken from the abstract in Bronn's Thierreichs.
A third, and in some respects very curious, form is a worm like larva of Müller, which is without bands of cilia. The dorsal surface of the youngest larva is divided by transverse constrictions into five segments. On the under side of the first of these is a five-lobed disc, each lobe being provided with a pair of tube feet.
At a later period only three segments are visible on the dorsal surface, but the ventral surface has assumed a pentagonal aspect. The later stages are not known.
[FIG. 261. DIAGRAMMATIC FIGURES SHEWING THE EVOLUTION OF AN OPHIUROID PLUTEUS FROM A SIMPLE ECHINODERM LARVA. (Copied from Müller.) The calcareous skeleton is not represented.
m. mouth; an. anus; d. anterior arms; d´. lateral arms; e´. posterior arms; g´. anterolateral arms.]
Ophiuroidea. The full-grown larva of the Ophiuroids is known as a Pluteus. It commences with the usual more or less spherical form; from this it passes to a form closely resembling that of Auricularia with a rounded dorsal surface, and a flattened ventral one. Soon however it becomes distinguished by the growth of a post-anal lobe and the absence of a præ-oral lobe (fig. 261 B). The post-anal lobe forms the somewhat rounded apex of the body. In front of the mouth, and between the mouth and anus, arise the anal and oral ciliated ridges, which soon become continued into a single longitudinal ciliated ring. At the same time the body becomes prolonged into a series of processes along the ciliated band, which is continued to the extremity of each. The primitive ciliated ring never becomes broken up into two or more rings. A ciliated crown is usually developed at the extremity of the post-anal lobe. The arms are arranged in the form of a ring surrounding the mouth, and are all directed forwards.
The first arms to appear are two lateral ones, which usually remain the most conspicuous (fig. 261 B and C, d´). Next arises a pair on the sides of the mouth, which may be called the mouth or anterior arms (C, d). A pair ventral to and behind the lateral arms is then formed, constituting the posterior arms (D, e´), and finally a pair between the lateral arms and the anterior, constituting the anterolateral arms (D, g´).
The concave area between the arms forms the greater part of the ventral surface of the body. Even before the appearance of any of the arms, and before the formation of the mouth, two calcareous rods are formed, which meet behind at the apex of the post-anal lobe, and are continued as a central support into each of the arms as they are successively formed. These rods are shewn at their full development in fig. 262. The important points which distinguish a Pluteus larva from the Auricularia or Bipinnaria are the following:
(1) The presence of the post-anal lobe at the hind end of the body. (2) The slight development of a præ-oral lobe. (3) The provisional calcareous skeleton in the larval arms.
[FIG. 262. PLUTEUS LARVA OF AN OPHIUROID. (From Gegenbaur; after Müller.)
A. rudiment of young Ophiuroid; d´. lateral arms; d. anterior arms; e´. posterior arms.]
Great variations are presented in the development of the arms and provisional skeleton. The presence of lateral arms is however a distinctive characteristic of the Ophiuroid Pluteus. The other arms may be quite absent, but the lateral arms never.
The formation of the permanent Ophiuroid takes place in much the same way as in the Asteroidea.
There is formed (fig. 262) on the right and dorsal side of stomach the abactinal disc supported by calcareous plates, at first only five in number and radial in position[223]. The disc is at first not symmetrical, but becomes so at the time of the resorption of the larval arms. It grows out into five processes--the five future rays. The original five radial plates remain as the terminal segments of the adult rays, and new plates are always added between the ultimate and penultimate plate (Müller), though it is probable that in the later stages fresh plates are added in the disc.
[223] Whether interradial plates are developed as in Asterias is not clear. They seem to be found in Ophiopholis bellis, Agassiz, but have not been recognised in other forms (vide Carpenter, No. 548, p. 369).
[FIG. 263. DIAGRAMMATIC FIGURES SHEWING THE EVOLUTION OF ECHINOID PLUTEI. (Copied from Müller.) The calcareous skeleton is not represented. E. Pluteus of Spatangus.
m. mouth; an. anus; d. anterior arms; d´. point where lateral arms arise in the Ophiuroid Pluteus; e. anterointernal arms; e´. posterior arms; g´. anterolateral arms; g. anteroexternal arms.]
The ventral surface of the permanent Ophiuroid is formed by the concave surface between the mouth and anus. Between this and the stomach is situated the water-vascular ring. It is at first not closed, but is horseshoe-shaped, with five blind appendages (fig. 262). It eventually grows round the oesophagus, which, together with the larval mouth, is retained in the adult. The five blind appendages become themselves lobed in the same way as in Asterias, and grow out along the five arms of the disc and become the radial canals and tentacles. All these parts of the water-vascular system are of course covered by skin, and probably also surrounded by mesoblast cells, in which at a later period the calcareous plates which lie ventral to the radial canal are formed. The larval anus disappears. As long as the larval appendages are not absorbed the ventral and dorsal discs of the permanent Ophiuroid fit as little as in the case of the Brachiolaria, but at a certain period the appendages are absorbed. The calcareous rods of the larval arms break up, the arms and anal lobe become absorbed, and the dorsal and ventral discs, with the intervening stomach and other organs, are alone left. After this the discs fit together, and there is thus formed a complete young Ophiuroid.
The whole of the internal organs of the larva (except the anus), including the mouth, oesophagus, the body cavity, etc. are carried on directly into the adult.
The larval skeleton is, as above stated, absorbed.
The viviparous larva of Amphiura squamata does not differ very greatly from the larvæ with very imperfect arms. It does not develop a distinct ciliated band, and the provisional skeleton is very imperfect. The absence of these parts, as well as of the anus, mentioned on p. 549, may probably be correlated with the viviparous habits of the larva. With reference to the passage of this larva into the adult there is practically nothing to add to what has just been stated. When the development of the adult is fairly advanced the part of the body with the provisional skeleton forms an elongated rod-like process attached to the developing disc. It becomes eventually absorbed.
[FIG. 264. TWO LARVÆ OF STRONGYLOCENTRUS. (From Agassiz.)
m. mouth; a. anus; o. oesophagus; d. stomach; c. intestine; v´. and v. ciliated ridges; w. water-vascular tube; r. calcareous rods.]
Echinoidea. The Echinus larva (fig. 263) has a Pluteus form like that of the Ophiuroids, and in most points, such as the presence of the anal lobe, the ciliated band, the provisional skeleton, etc., develops in the same manner. The chief difference between the two Pluteus forms concerns the development of the lateral arms. These, which form the most prominent arms in the Ophiuroid Pluteus, are entirely absent in the Echinoid Pluteus, which accordingly has, as a rule, a much narrower form than the Ophiuroid Pluteus.
A pair of ciliated epaulettes on each side of and behind the ciliated ring is very characteristic of some Echinoid larvæ. They are originally developed from the ciliated ring (fig. 266 A and B, v´´). The presence of three processes from the anal lobe supported by calcareous rods is characteristic of the Spatangoid Pluteus (fig. 263 E).
[FIG. 265. LATERAL AND VENTRAL VIEW OF A LARVA OF STRONGYLOCENTRUS. (From Agassiz.) General references as in fig. 264.
b. dorsal opening of madreporic canal; e´. posterior arms; e´´´. anterior arms; eIV. anterointernal arms.]
The first two pairs of arms to develop, employing the same names as in Ophiuroids, are the anterior attached to the oral process (fig. 263 C, d) and the posterior pair (e´). A pair of anterolateral arms next becomes developed (g´). A fourth pair (not represented in Ophiuroids) appears on the inner side of the anterior pair forming an anterointernal pair (e), and in the Spatangoid Pluteus a fifth pair may be added on the external side of the anterior pair forming an anteroexternal pair (g).
Each of the first-formed paired calcareous rods is composed of three processes, two of which extend into the anterior and posterior arms; and the third and strongest passes into the anal lobe, and there meets its fellow (fig. 265). A transverse bar in front of the arms joins the rods of the two sides meeting them at the point where the three processes diverge. The process in the anterolateral arm (fig. 266 B) is at first independent of this system of rods, but eventually unites with it. Although our knowledge of the Pluteus types in the different groups is not sufficient to generalise with great confidence, a few points seem to have been fairly determined[224]. The Plutei of Strongylocentrus (figs. 266 and 267) and Echinus have eight arms and four ciliated epaulettes. The only Cidaris-like form, the Pluteus of which is known, is Arbacia: it presents certain peculiarities. The anal lobe develops a pair of posterior (auricular) appendages, and the ciliated ring, besides growing out into the normal eight appendages, has a pair of short blunt anterior and posterior lobes. An extra pair of non-ciliated accessory mouth arms appears also to be developed. Ciliated epaulettes are not present. So far as is known the Clypeastroid larva is chiefly characterized by the round form of the anal lobe. The calcareous rods are latticed. In the Pluteus of Spatangoids there are (fig. 263) five pairs of arms around the mouth pointing forwards, and three arms developed from the anal lobe pointing backwards. One of these is unpaired, and starts from the apex of the anal lobe. All the arms have calcareous rods which, in the case of the posterior pair, the anterolateral pair, and the unpaired arm of the anal lobe, are latticed. Ciliated epaulettes are not developed.
[224] Vide especially Müller, Agassiz, and Metschnikoff.
Viviparous larvæ of Echinoids have been described by Agassiz[225].
[225] For viviparous Echini vide Agassiz, Proc. Amer. Acad. 1876.
The development of the permanent Echinus has been chiefly worked out by Agassiz and Metschnikoff.
In the Pluteus of Echinus lividus the first indication of the adult arises, when three pairs of arms are already developed, as an invagination of the skin on the left side, between the posterior and anterolateral arms, the bottom of which is placed close to the water-vascular vesicle (fig. 266 B, w´). The base of this invagination becomes very thick, and forms the ventral disc of the future Echinus. The parts connecting this disc with the external skin become however thin, and, on the narrowing of the external aperture of invagination and the growth of the thickened disc, constitute a covering for the disc, called by Metschnikoff the amnion. The water-vascular vesicle adjoining this disc grows out into five processes, forming as many tube feet, which cause the surface of the involuted disc to be produced into the same number of processes. The external opening of the invagination of the disc never closes, and after the development of the tube feet begins to widen again, and the amnion to atrophy. Through the opening of the invagination the tube feet now project. The dorsal and right surface of the Pluteus, which extends so as to embrace the opening of the madreporic canal and the anus, forms the abactinal or dorsal surface of the future Echinus (fig. 267, a). This disc fits on to the actinal invaginated surface which arises on the left side of the Pluteus. On the right surface of the larva (dorsal of permanent Echinus) two pedicellariæ appear, and at a later period spines are formed, which are at first arranged in a ring-like form round the edge of the primitively flat test. While these changes are taking place, and the two surfaces of the future Echinus are gradually moulding themselves so as to form what is obviously a young Echinus, the arms of the Pluteus with their contained skeleton have been gradually undergoing atrophy. They become irregular in form, their contained skeleton breaks up into small pieces, and they are gradually absorbed.
[FIG. 266. SIDE AND DORSAL VIEW OF A LARVA OF STRONGYLOCENTRUS. (From Agassiz.) General reference letters as in figs. 264 and 265.
e´´. anterolateral arms; v´´. ciliated epaulettes; w´. invagination to form the disc of Echinus.]
The water-vascular ring is from the first complete, so that, as in Asterias, it is perforated through the centre by a new oesophagus. According to Agassiz the first five tentacles or tube feet grow into the radial canals, and form the odd terminal tentacles exactly as in Asterias[226]. Spatangus only differs in development from Echinus in the fact that the opening of the invagination to form the ventral disc becomes completely closed, and that the tube feet have eventually to force their way through the larval epidermis of the amnion, which is ruptured in the process and eventually thrown off.
[226] Götte (No. 549) supported by Müller's and Krohn's older, and in some points extremely erroneous observations, has enunciated the view that the radial canals in Echinoids and Holothuroids have a different nature from those in Asteroids and Ophiuroids.
[FIG. 267. FULL-GROWN LARVA OF STRONGYLOCENTRUS. (From Agassiz.)
The figure shews the largely-developed abactinal disc of the young Echinus enclosing the larval stomach. Reference letters as in previous figs.]
Crinoidea. The larva of Antedon, while still within the egg-shell, assumes an oval form and uniform ciliation. Before it becomes hatched the uniform layer of cilia is replaced by four transverse bands of cilia, and a tuft of cilia at the posterior extremity. In this condition it escapes from the egg-shell (fig. 268 A), and becomes bilateral, owing to a flattening of the ventral surface. On the flattened surface appears a ciliated depression corresponding in position with the now closed blastopore (vide p. 550). The third ciliated band bends forward to pass in front of this (fig. 269). Behind the last ciliated band there is present a small depression of unknown function, also situated on the ventral surface. The posterior extremity of the embryo elongates to form the rudiment of the future stem, and a fresh depression, marking the position of the future mouth, makes its appearance on the anterior and ventral part.
[FIG. 268. THREE STAGES IN THE DEVELOPMENT OF ANTEDON (COMATULA.) (From Lubbock; after Thomson.)
A. larva just hatched; B. larva with rudiment of the calcareous plates; C. Pentacrinoid larva.]
While the ciliated bands are still at their full development, the calcareous skeleton of the future calyx makes its appearance in the form of two rows, each of five plates, formed of a network of spicula (figs. 268 B and 269). The plates of the anterior ring are known as the orals, those of the posterior as the basals. The former surround the left, i.e. anterior peritoneal sack; the latter the right, i.e. posterior peritoneal sack. The two rows of plates are at first not quite transverse, but form two oblique circles, the dorsal end being in advance of the ventral. The rows soon become transverse, while the originally somewhat ventral oral surface is carried into the centre of the area enclosed by the oral plates.
[FIG. 269. LARVA OF ANTEDON WITH RUDIMENTS OF CALCAREOUS SKELETON. (From Carpenter; after Thomson.)
1. Terminal plate at the end of the stem; 3. basals; or. orals; bl. position of blastopore.]
By the change in position of the original ventral surface relatively to the axis of the body, the bilateral symmetry of the larva passes into a radial symmetry. While the first skeletal elements of the calyx are being formed, the skeleton of the stem is also established. The terminal plate is first of all established, then the joints, eight at first, of the stem. The centro-dorsal plate is stated by Thomson to be formed as the uppermost joint of the stem[227]. The larva, after the completion of the above changes, is shewn in fig. 268 B, and somewhat more diagrammatically in fig. 269.
[227] Götte (No. 549) on the other hand holds that the centro-dorsal plate is developed by the coalescence of a series of at first independent rods, which originate simultaneously with, and close to, the lower edges of the basals, and that it is therefore similar in its origin to the basals.
[FIG. 270. YOUNG PENTACRINOID LARVA OF ANTEDON. (From Carpenter; after Wyville Thomson.)
1. terminal plate of stem; cd. centro-dorsal plate; 3. basals; 4. radials; or. orals.]
After the above elements of the skeleton have become established the ciliated bands undergo atrophy, and shortly afterwards the larva becomes attached by the terminal plate of its stem. It then passes into the Pentacrinoid stage. The larva in this stage is shewn in fig. 268 C and fig. 270. New joints are added at the upper end of the stem next the calyx, and a new element--the radials--makes its appearance as a ring of five small plates, placed in the space between the basals and orals, and in the intervals alternating with them (fig. 270, 4). The roof of the oral vestibule (vide fig. 253 and p. 551) has in the meantime become ruptured; and the external opening of the mouth thus becomes established. Surrounding the mouth are five petal-like lobes, each of them supported by an oral plate (fig. 268 C). In the intervals between them five branched and highly contractile tentacles, which were previously enclosed within the vestibule, now sprout out: they mark the position of the future radial canals, and are outgrowths of the water-vascular ring. At the base of each of them a pair of additional tentacles is soon formed. Each primary tentacle corresponds to one of the radials. These latter are therefore, as their name implies, radial in position; while the basals and orals are interradial. In addition to the contractile radial tentacles ten non-contractile tentacles, also diverticula of the water-vascular ring, are soon formed, two for each interradius.
In the course of the further development the equatorial space between the orals and the basals enlarges, and gives rise to a wide oral disc, the sides of which are formed by the radials resting on the basals; while in the centre of it are placed the five orals, each with its special lobe.
The anus, which is formed on the ventral side in the position of the blastopore (p. 551), becomes surrounded by an anal plate, which is interradial in position, and lies on the surface of the oral disc between the orals and radials. On the oral plate in the next interradius is placed the opening of a single funnel leading into the body cavity, which Ludwig regards as equivalent to the opening of the madreporic canal (vide p. 551)[228].
[228] I have made no attempt to discuss the homologies of the plates of the larval Echinodermata because the criteria for such a discussion are still in dispute. The suggestive memoirs of P. H. Carpenter (No. 548) on this subject may be consulted by the reader. Carpenter attempts to found his homologies on the relation of the plates to the primitive peritoneal vesicles, and I am inclined to believe that this method of dealing with these homologies is the right one. Ludwig (No. 559) by regarding the opening of the madreporic canal as a fixed point has arrived at very different results.
From the edge of the vestibule the arms grow out, carrying with them the tentacular prolongation of the water-vascular ring. Two additional rows of radials are soon added.
The stalked Pentacrinoid larva becomes converted, on the absorption of the stalk, into the adult Antedon. The stalk is functionally replaced by a number of short cirri springing from the centro-dorsal plate. The five basals coalesce into a single plate, known as the rosette, and the five orals disappear, though the lobes on which they were placed persist. In some stalked forms, e.g. Rhizocrinus Hyocrinus, the orals are permanently retained. The arms bifurcate at the end of the third radial, and the first radial becomes in Antedon rosacea (though not in all species of Antedon) concealed from the surface by the growth of the centro-dorsal plate. An immense number of funnels, leading into the body cavity, are formed in addition to the single one present in the young larva. These are regarded by Ludwig as equivalent to so many openings of the madreporic canal; and there are developed, in correspondence with them, diverticula of the water-vascular ring.
Comparison of Echinoderm Larvæ and General Conclusions.
In any comparison of the various types of Echinoderm larvæ it is necessary to distinguish between the free-swimming forms, and the viviparous or fixed forms. A very superficial examination suffices to shew that the free-swimming forms agree very much more closely amongst themselves than the viviparous forms. We are therefore justified in concluding that in the viviparous forms the development is abbreviated and modified.
All the free forms are nearly alike in their earliest stage after the formation of the archenteron. The surface between the anus and the future mouth becomes flattened, and (except in Antedon, Cucumaria, Psolinus, etc. which practically have an abbreviated development like that of the viviparous forms) a ridge of cilia becomes established in front of the mouth, and a second ridge between the mouth and the anus. This larval form, which is shewn in fig. 264 A, is the type from which the various forms of Echinoderm larvæ start.
In all cases, except in Bipinnaria, the two ciliated ridges soon become united, and constitute a single longitudinal post-oral ciliated ring.
The larvæ in their further growth undergo various changes, and in the later stages they may be divided into two groups:
(1) The Pluteus larva of Echinoids and Ophiuroids.
(2) The Auricularia (Holothuroids) and Bipinnaria (Asteroids) type.
The first group is characterized by the growth of a number of arms more or less surrounding the mouth, and supported by calcareous rods. The ciliated band retains its primitive condition as a simple longitudinal band throughout larval life. There is a very small præ-oral lobe, while an anal lobe is very largely developed.
[FIG. 271. A. THE LARVA OF A HOLOTHUROID. B. THE LARVA OF AN ASTERIAS.
m. mouth; st. stomach; a. anus; l.c. primitive longitudinal ciliated band; pr.c. præ-oral ciliated band.]
The Auricularia and Bipinnaria resemble each other in shape, in the development of a large præ-oral lobe, and in the absence of provisional calcareous rods; but differ in the fact that the ciliated band is single in Auricularia (fig. 271 A), and is double in Bipinnaria (fig. 271 B).
The Bipinnaria larva shews a great tendency to develop soft arms; while in the Auricularia the longitudinal ciliated band breaks up into a number of transverse ciliated bands. This condition is in some instances reached directly, and such larvæ undoubtedly approximate to the larvæ of Antedon, in which the uniformly ciliated condition is succeeded by one with four transverse bands, of which one is præ-oral.
All or nearly all Echinoderm larvæ are bilaterally symmetrical, and since all Echinodermata eventually attain a radial symmetry, a change necessarily takes place from the bilateral to the radial type.
In the case of the Holothurians and Antedon, and generally in the viviparous types, this change is more or less completely effected in the embryonic condition; but in the Bipinnaria and Pluteus types a radial symmetry does not become apparent till after the absorption of the larval appendages. It is a remarkable fact, which seems to hold for the Asteroids, Ophiuroids, Echinoids, and Crinoids, that the dorsal side of the larva is not directly converted into the dorsal disc of the adult; but the dorsal and right side becomes the adult dorsal or abactinal surface, while the ventral and left becomes the actinal or ventral surface.
It is interesting to note with reference to the larvæ of the Echinodermata that the various existing types of larvæ must have been formed after the differentiation of the existing groups of the Echinodermata; otherwise it would be necessary to adopt the impossible position that the different groups of Echinodermata were severally descended from the different types of larvæ. The various special appendages, etc. of the different larvæ have therefore a purely secondary significance; and their atrophy at the time of the passage of the larva into the adult, which is nothing else but a complicated metamorphosis, is easily explained.
Originally, no doubt, the transition from the larva to the adult was very simple, as it is at present in most Holothurians; but as the larvæ developed various provisional appendages, it became necessary that these should be absorbed in the passage to the adult state.
It would obviously be advantageous that their absorption should be as rapid as possible, since the larva in a state of transition to the adult would be in a very disadvantageous position. The rapid metamorphosis, which we find in Asteroids, Ophiuroids, and Echinoids in the passage from the larval to the adult state, has no doubt arisen for this reason.
In spite of the varying provisional appendages possessed by Echinoderm larvæ it is possible, as stated above (p. 574), to recognise a type of larva, of which all the existing Echinoderm larval forms are modifications. This type does not appear to me to be closely related to that of the larvæ of any group described in the preceding pages. It has no doubt certain resemblances to the trochosphere larva of Chætopoda, Mollusca, etc., but the differences between the two types are more striking than the resemblances. It firstly differs from the trochosphere larva in the character of the ciliation. Both larvæ start from the uniformly ciliated condition, but while the præ-oral ring is almost invariable, and a peri-anal ring very common in the trochosphere; in the Echinoderm larva such rings are rarely found; and even when present, i.e. the præ-oral ring of Bipinnaria and the terminal though hardly peri-anal patch of Antedon, do not resemble closely the more or less similar structures of the trochosphere. The two ciliated ridges (fig. 264 A) common to all the Echinoderm larvæ, and subsequently continued into a longitudinal ring, have not yet been found in any trochosphere. The transverse ciliated rings of the Holothurian and Crinoid larvæ are of no importance in the comparison between the trochosphere larvæ and the larvæ of Echinodermata, since such rings are frequently secondarily developed. Cf. Pneumodermon and Dentalium amongst Mollusca.
In the character of the præ-oral lobe the two types again differ. Though the præ-oral lobe is often found in Echinoderm larvæ it is never the seat of an important (supra-oesophageal) ganglion and organs of special sense, as it invariably is in the trochosphere.
Nothing like the vaso-peritoneal vesicles of the Echinoderm larvæ has been found in the trochosphere; nor have the characteristic trochosphere excretory organs been found in the Echinoderm larvæ.
The larva which most nearly approaches those of the Echinodermata is the larva of Balanoglossus described in the next chapter.
BIBLIOGRAPHY.
(542) Alex. Agassiz. Revision of the Echini. Cambridge, U.S. 1872-74.
(543) Alex. Agassiz. "North American Starfishes." Memoirs of the Museum of Comparative Anatomy and Zoology at Harvard College, Vol. V., No. 1. 1877 (originally published in 1864).
(544) J. Barrois. "Embryogénie de l'Asteriscus verruculatus." Journal de l'Anat. et Phys. 1879.
(545) A. Baur. Beiträge zur Naturgeschichte d. Synapta digitata. Dresden, 1864.
(546) H. G. Bronn. Klassen u. Ordnungen etc. Strahlenthiere, Vol. II. 1860.
(547) W. B. Carpenter. "Researches on the structure, physiology and development of Antedon." Phil. Trans. CLVI. 1866, and Proceedings of the Roy. Soc., No. 166. 1876.
(548) P. H. Carpenter. "On the oral and apical systems of the Echinoderms." Quart. J. of Micr. Science, Vol. XVIII. and XIX. 1878-9.
(549) A. Götte. "Vergleichende Entwicklungsgeschichte d. Comatula mediterranea." Arch. für micr. Anat., Vol. XII. 1876.
(550) R. Greeff. "Ueber die Entwicklung des Asteracanthion rubens vom Ei bis zur Bipinnaria u. Brachiolaria." Schriften d. Gesellschaft zur Beförderung d. gesammten Naturwissenschaften zu Marburg, Bd. XII. 1876.
(551) R. Greeff. "Ueber den Bau u. die Entwicklung d. Echinodermen." Sitz. d. Gesell. z. Beförderung d. gesam. Naturwiss. zu Marburg, No. 4. 1879.
(552) T. H. Huxley. "Report upon the researches of Müller into the anat. and devel. of the Echinoderms." Ann. and Mag. of Nat. Hist., 2nd Ser., Vol. VIII. 1851.
(553) Koren and Danielssen. "Observations sur la Bipinnaria asterigera." Ann. Scien. Nat., Ser. III., Vol. VII. 1847.
(554) Koren and Danielssen. "Observations on the development of the Starfishes." Ann. and Mag. of Nat. Hist., Vol. XX. 1857.
(555) A. Kowalevsky. "Entwicklungsgeschichte d. Holothurien." Mém. Ac. Pétersbourg, Ser. VII., Tom. XI., No. 6.
(556) A. Krohn. "Beobacht. a. d. Entwick. d. Holothurien u. Seeigel." Müller's Archiv, 1851.
(557) A. Krohn. "Ueb. d. Entwick. d. Seesterne u. Holothurien." Müller's Archiv, 1853.
(558) A. Krohn. "Beobacht. üb. Echinodermenlarven." Müller's Archiv, 1854.
(559) H. Ludwig. "Ueb. d. primar. Steinkanal d. Crinoideen, nebst vergl. anat. Bemerk. üb. d. Echinodermen." Zeit. f. wiss. Zool., Vol. XXXIV. 1880.
(560) E. Metschnikoff. "Studien üb. d. Entwick. d. Echinodermen u. Nemertinen." Mém. Ac. Pétersbourg, Series VII., Tom. XIV., No. 8. 1869.
(561)[229] Joh. Müller. "Ueb. d. Larven u. d. Metamorphose d. Echinodermen." Abhandlungen d. Berlin. Akad. (Five Memoirs), 1848, 49, 50, 52 (two Memoirs).
(562) Joh. Müller. "Allgemeiner Plan d. Entwicklung d. Echinodermen." Abhandl. d. Berlin. Akad., 1853.
(563) E. Selenka. "Zur Entwicklung d. Holothurien." Zeit. f. wiss. Zool., Bd. XXVII. 1876.
(564) E. Selenka. "Keimblätter u. Organanlage bei Echiniden." Zeit. f. wiss. Zool., Vol. XXXIII. 1879.
(565) Sir Wyville Thomson. "On the Embryology of the Echinodermata." Natural History Review, 1864.
(566) Sir Wyville Thomson. "On the Embryogeny of Antedon rosaceus." Phil. Trans. 1865.
[229] The dates in this reference are the dates of publication.
XXI. ENTEROPNEUSTA
The larva of Balanoglossus is known as Tornaria. The præ-larval development is not known, and the youngest stage (fig. 272) so far described (Götte, No. 569) has many remarkable points of resemblance to a young Bipinnaria.
[FIG. 272. EARLY STAGE IN THE DEVELOPMENT OF TORNARIA. (After Götte.)
W. so-called water-vascular vesicle developing as an outgrowth of the mesenteron; m. mouth; an. anus.]
A mouth (m), situated on the ventral surface, leads into an alimentary canal with a terminal anus (an). A præ-oral lobe is well developed, as in Bipinnaria, but there is no post-anal lobe. The bands of cilia have the same general form as in Bipinnaria. There is a præ-oral band, and a longitudinal post-oral band; and the two bands nearly meet at the apex of the præ-oral lobe (fig. 273). A contractile band passes from the oesophagus to the apex of the præ-oral lobe, and a diverticulum (fig. 272, W) from the alimentary tract, directed towards the dorsal surface, is present. Contractile cells are scattered in the space between the body wall and the gut.
In the following stage (fig. 274 A) a conspicuous transverse post-oral band of a single row of long cilia is formed, and the original bands become more sinuous. The alimentary diverticulum of the last stage becomes an independent vesicle opening by a pore on the dorsal surface (fig. 274 A, w). The contractile cord is now inserted on this vesicle. Where this cord joins the apex of the præ-oral lobe between the two anterior bands of cilia a thickening of the epiblast (? a ganglion) has become established, and on it are placed two eye-spots (fig. 273 oc, and fig. 274 A). A deep bay is formed on the ventral surface of the larva.
[FIG. 273. YOUNG TORNARIA. (After Müller.)
m. mouth; an. anus; w. water-vascular vesicle; oc. eye-spots; c.c. contractile cord.]
[FIG. 274. TWO STAGES IN THE DEVELOPMENT OF TORNARIA. (After Metschnikoff.)
The black lines represent the ciliated bands. m. mouth; an. anus; br. branchial cleft; ht. heart; c. body cavity between splanchnic and somatic mesoblast layers; w. water-vascular vesicle; v. circular blood-vessel.]
As the larva grows older the original bands of cilia become more sinuous, and a second transverse band with small cilia is formed (in the Mediterranean larva) between the previous transverse band and the anus. The water-vascular vesicle is prolonged into two spurs, one on each side of the stomach. A pulsating vesicle or heart is also formed (fig. 274 B, ht), and arises, according to Spengel (No. 572), as a thickening of the epidermis. It subsequently becomes enveloped in a pericardium, and is placed in a depression in the water-vascular vesicle. Two pairs of diverticula, one behind the other, grow out (Agassiz, No. 568) from the gastric region of the alimentary canal. The two parts of each pair form flattened compartments, which together give rise to a complete investment of the adjoining parts of the alimentary tract. The two parts of each coalesce, and thus form a double-walled cylinder round the alimentary tract, but their cavities remain separated by a dorsal and ventral septum.
Eventually (Spengel) the cavity of the anterior cylinder forms the section of the body cavity in the collar of the adult, and that of the posterior (fig. 274 B, c) the remainder of the body cavity. The septa, separating the two halves of each, remain as dorsal and ventral mesenteries.
The conversion of Tornaria (fig. 274 A) into Balanoglossus (fig. 274 B) is effected in a few hours, and consists mainly in certain changes in configuration, and in the disappearance of the longitudinal ciliated band.
The body of the young Balanoglossus (fig. 274 B) is divided into three regions (1) the proboscidian region, (2) the collar, (3) the trunk proper. The proboscidian region is formed by the elongation of the præ-oral lobe into an oval body with the eye-spots at its extremity, and provided with strong longitudinal muscles. The heart (ht) and water-vascular vesicle lie near its base, but the contractile cord connected with the latter is no longer present. The mouth is placed on the ventral side at the base of the præ-oral lobe, and immediately behind it is the collar. The remainder of the body is more or less conical, and is still girt with the larval transverse ciliated band, which lies in the middle of the gastric region in the Mediterranean species, but in the oesophageal region in the American one.
The whole of the body, including the proboscis, becomes richly ciliated.
One of the most important characters of the adult Balanoglossus consists in the presence of respiratory structures comparable with the vertebrate gill slits. The earliest traces of these structures are distinctly formed while the larva is still in the Tornaria condition, as one pair of pouches from the oesophagus in the Mediterranean species, and four pairs in the American one (fig. 275, br).
[FIG. 275. LATE STAGE IN THE DEVELOPMENT OF BALANOGLOSSUS WITH FOUR BRANCHIAL CLEFTS. (After Alex. Agassiz.)
m. mouth; an. anus; br. branchial cleft; ht. heart; W. water-vascular vesicle.]
In the Mediterranean Tornaria the two pouches meet the skin dorsally, and in the young Balanoglossus (fig. 274 B, br) acquire an external opening on the dorsal side. In the American species the first four pouches are without external openings till additional pouches have been formed. Fresh gill pouches continue to be formed both in the American and probably the Mediterranean species, but the conversion of the simple pouches into the complicated gill structure of the adult has only been studied by Agassiz (No. 568) in the American species. It would seem in the first place that the structure of the adult gill slits is much less complicated in the American than in the Mediterranean species. The simple pouches of the young become fairly numerous. They are at first circular; they then become elliptical, and the dorsal wall of each slit becomes folded; subsequently fresh folds are formed which greatly increase the complexity of the gills. The external openings are not acquired till comparatively late.
Our knowledge of the development of the internal organs, mainly derived from Agassiz, is still imperfect. The vascular system appears early in the form of a dorsal and a ventral vessel, both pointed, and apparently ending blindly at their two extremities. The two spurs of the water-vascular vesicle, which in the Tornaria stage rested upon the stomach, now grow round the oesophagus, and form an anterior vascular ring, which Agassiz describes as becoming connected with the heart, though it still communicates with the exterior by the dorsal pore and seems to become connected with the remainder of the vascular system. According to Spengel (No. 572) the dorsal vessel becomes connected with the heart, which remains through life in the proboscis: the cavity of the water-vascular vesicle forms the cavity of the proboscis in the adult, and its pore remains as a dorsal (not, as usually stated, ventral) pore leading to the exterior.
The eye-spots disappear.
Tornaria is a very interesting larval form, since it is intermediate in structure between the larva of an Echinoderm and trochosphere type common to the Mollusca, Chætopoda, etc. The shape of the body especially the form of the ventral depression, the character of the longitudinal ciliated band, the structure and derivation of the water-vascular vesicle, and the formation of the walls of the body cavity as gastric diverticula, are all characters which point to a connection with Echinoderm larvæ.
On the other hand the eye-spots at the end of the præ-oral lobe[230], the contractile band passing from the oesophagus to the eye-spots (fig. 273), the two posterior bands of cilia, and the terminal anus are all trochosphere characters.
[230] It would be interesting to have further information about the fate of the thickening of epiblast in the vicinity of the eye-spots. The thickening should by rights be the supra-oesophageal ganglion, and it does not seem absolutely impossible that it may give rise to the dorso-median cord in the region of the collar, which constitutes, according to Spengel, the main ganglion of the adult.
The persistence of the præ-oral lobe as the proboscis is interesting, as tending to shew that Balanoglossus is the surviving representative of a primitive group.
BIBLIOGRAPHY.
(567) A. Agassiz. "Tornaria." Ann. Lyceum Nat. Hist. VIII. New York, 1866.
(568) A. Agassiz. "The History of Balanoglossus and Tornaria." Mem. Amer. Acad. of Arts and Scien., Vol. IX. 1873.
(569) A. Götte. "Entwicklungsgeschichte d. Comatula Mediterranea." Archiv für mikr. Anat., Bd. XII., 1876, p. 641.
(570) E. Metschnikoff. "Untersuchungen üb d. Metamorphose, etc. (Tornaria)." Zeit. für wiss. Zool., Bd. XX. 1870.
(571) J. Müller. "Ueb. d. Larven u. Metamor. d. Echinodermen." Berlin Akad., 1849 and 1850.
(572) J. W. Spengel. "Bau u. Entwicklung von Balanoglossus." Tagebl. d. Naturf. Vers. München, 1877.
INDEX.
Abdominalia, 459, 493, 499
Acanthocephala, 379
Acanthosoma, 473, 474, 475
Acarina, 444, 454
Accipenser, 102
Achæta, 319
Achelia, 538
Achtheres percarum, 490
Acineta, 7, 8
Acraspeda, 152, 165, 167, 178, 179, 182, 185, 186
Actinia, 169, 171, 179
Actinophrys, 9
Actinotrocha, 315, 318, 363, 364
Actinozoa, 26, 102, 152, 166, 170, 171, 172, 176, 178, 179, 181, 182, 186
Actinula, 155
Aculeata, 421
Ægineta flavescens, 158
Æginidæ, 156, 158
Æginopsis Mediterranea, 158
Æquorea Mitrocoma, 182
Agalma, 163
Agelena, 436, 450
Agelena labyrinthica, 119, 438
Alciope, 74
Alcippidæ, 499
Alcyonaria, 152
Alcyonidæ, 167, 168
Alcyonidium mytili, 297, 300, 302
Alcyonium palmatum, 119, 148, 167, 182
Alima, 484, 486
Amoeba, 19, 20
Amphibia, 22, 54, 56, 59, 60, 63, 66, 74, 83, 102
Amphilina, 218
Amphioxus, 54, 56, 59, 61, 66, 93, 426
Amphipoda, 518
Amphiporus lactifloreus, 202
Amphistomum, 31
" subclavatum, 205
Amphitrochæ, 330
Amphiura squamata, 565
Anchorella, 108, 492, 520
Anelasma squalicola, 499
Anguillulidæ, 371
Annelida, 14, 25, 98, 503, 525
Anodon, 37, 38, 39, 100, 107, 259, 260, 265, 266, 268
Anopla, 189, 202
Anura, 5
Antedon, 568, 573, 574
Aphides, 15, 16, 76, 79, 116, 428, 429
Aphrodite, 42
Apis, 402, 407, 408, 412, 413
Aplysia, 99, 226, 238, 252, 253
Aplysinidæ, 146
Apoda, 459, 493
Aptera, 395, 420
Apus, 16, 79, 460, 463
Arachnida, 22, 114, 119, 413, 431, 435, 444, 454, 455, 458, 537, 539
Arachnitis, 171
Araneina, 50, 51, 436
Arbacia, 567
Arca, 38
Archigetes, 218
Archizoæa gigas, 494
Arenicola, 42
Argiope, 311, 312, 315, 317
Argonauta, 247, 248
Argulus, 492
Armata, 355
Arthropoda, 12, 16, 18, 22, 75, 77, 79, 83, 108, 110, 221, 382, 383, 434, 448, 503, 525, 534, 541, 542
Articulata, 311, 313, 316, 317
Ascaridiæ, 371
Ascaris nigrovenosa, 16, 82
" lumbricoides, 375
Ascetta, 144
Ascidia canina, 53
Ascidians, 74, 102, 208, 426
Asellus aquaticus, 112, 120, 516
Astacus, 66, 465, 477, 511, 512, 513, 525
Asteracanthion, 69, 70, 561
Asterias, 20, 68, 69, 71, 78, 80, 84, 549, 564
Asteroidea, 35, 36, 544, 549, 557, 563, 576
Astræa, 169
Astroides, 169
Atax Bonzi, 445
Atlanta, 231, 240
Atrochæ, 330
Aurelia, 167
Auricularia, 553, 554, 562, 574
Autolytus cornutus, 319, 343
Aves, 56, 59, 61, 64, 107, 109
Axolotl, 16
Balanoglossus, 576, 579, 581
Balanus balanoides, 75, 493
Belemnites, 252, 253
Bipinnaria, 557, 563, 574, 576, 579
Blatta, 374, 395
Bojanus, organ of, 264, 282
Bonellia, 20, 43, 44, 98, 324, 355, 358, 359
Bothriocephalus salmonis, 211
" proboscideus, 212
Brachiella, 492
Brachiolaria, 558, 564
Brachiopoda, 311, 317, 318
Brachyura, 466, 480, 483
Branchiobdella, 42, 43, 346
Branchiogasteropoda, 272
Branchiopoda, 79, 459, 523, 524
Branchipus, 463, 524
Branchiura, 459, 492
Branchionus urceolaris, 221
Braula, 396
Buccinum, 237, 280
Bulimus citrinas, 229
Bunodes, 169, 171
Buthus, 431
Calcispongiæ, 138, 148
Calopteryx, 402
Calycophoridæ, 152, 159
Calyptoblastic Hydroids, 184, 185
Calyptræa, 223, 280
Campanularidæ, 183, 184
Capitella, 330, 332
Carabidæ, 476
Carcinus Moenas, 481, 483
Cardium, 260, 262
" pygmæum, 262
Carinaria, 240
Caryophyllium, 168, 171
Cassiopea, 165, 167
Cecidomyia, 15, 79, 416, 417, 429
Cephalopoda, 20, 40, 41, 102, 108, 109, 135, 225, 240, 242, 244, 250, 252, 253, 270, 271, 272, 274, 279, 282, 287
Cephalothrix galatheae, 202
Ceratospongiæ, 146
Cercariae, 207, 208, 209
Cerianthus, 168, 171
Cestodes, 14, 29, 31, 32, 33, 189, 210, 212, 218, 313, 425, 541
Chætogaster, 342
Chætopoda, 5, 18, 23, 41, 43, 44, 54, 67, 209, 215, 270, 275, 307, 312, 317, 318, 319, 320, 326, 334, 338, 342, 346, 349, 350, 351, 364, 369, 383, 386, 408, 448, 457, 458, 521, 576, 582
Chætopteridæ, 333
Chætosomoidea, 371
Chelifer, 434, 436, 442, 446, 454
Chermes, 15, 429
Chilognatha, 113, 387, 389, 391, 393, 395
Chilopoda, 387, 393, 394
Chilostomata, 292, 297, 298, 304, 305
Chironomus, 15, 378, 401, 402, 415, 416, 429
Chiton, 254, 256, 257,273
Chordata, 5
Chrysaora, 165
Chthonius, 436
Cicada, 395
Cirripedia, 459, 492, 496, 503, 509, 520
Cladocera, 459, 464, 519
Clausilia, 239
Clavella, 520
Clavularia crassa, 167
Cleodora, 241
Clepsine, 73, 346, 347, 349, 351, 352, 353, 354
Clio, 242, 278
Clubione, 436
Clupeidæ, 64
Cobitis barbatula, 378
Coccidæ, 429
Coccus, 50
Coelebogyne, 79
Coelenterata, 3, 5, 13, 18, 26, 27, 28, 35, 74, 93, 94, 126, 148, 170, 178, 179, 180, 181, 191, 342
Coenurus cerebralis, 213, 214
Coleochæte, 11
Coleoptera, 396, 402, 409, 412, 420, 421, 425
Collembola, 395, 426
Comatula, 5, 552, 553
Condracanthus, 111, 120, 520
Conochilus volvox, 221
Convoluta, 32
Copepoda, 109, 120, 459, 460, 487, 489, 493, 496, 503, 509, 519
Corallium rubrum, 168, 182
Corethra, 422, 423, 424
Crangoninæ, 476
Craniadæ, 311
Craniata, 5, 6, 19, 20, 54, 56, 59, 61, 62, 64, 74, 102
Crinoidea, 35, 36, 544, 550, 568, 576
Criodilus, 321, 324, 328, 341
Crisia, 304
Crocodilia, 63
Crustacea, 5, 6, 18, 51, 66, 102, 109, 120, 458, 465, 487, 502, 521, 524, 537, 541
Cryptophialus, 499, 509
Crystalloides, 163
Ctenophora, 26, 93, 102, 152, 173, 175, 177, 178, 179, 180, 181, 182
Ctenostomata, 292, 297, 298, 304, 305
Cucullanus elegans, 46, 75, 82, 371, 376
Cucumaria, 546, 556, 574
Cumaceæ, 459, 465, 486, 506
Curculio, 421
Cyclas, 259, 260, 261, 265
Cyclops, 376, 377, 418, 489, 503
Cyclostomata, 102, 292, 304
Cymbulia, 241, 242
Cymothoa, 516, 517, 519, 520, 524, 528
Cynipidæ, 15, 421, 428
Cyphonautes, 297, 301, 304, 306, 308
Cypridina, 500, 502
Cysticercus cellulosæ, 214, 217
" fasciolaris, 216
" limacis, 213
Daphnia, 79, 464
Dasychone, 331, 336
Decapoda, 66, 248, 459, 465, 469, 504, 511
Dendrocoela, 32, 33, 189, 195, 196
Dentalium, 258, 576
Desmacidon, 147
Desor, type of, 196, 197, 201, 202, 204, 212, 424
Diastopora, 304
Dibranchiata, 225, 253
Dicyema, 9, 131, 134, 135, 136
Dimya, 225
Diphyes, 159
Diplozoon, 11, 209, 210
Diporpa, 210
Diptera, 49, 194, 204, 396, 401, 402, 407, 409, 412, 416, 420, 429
Discina radiata, 317
Discinidæ, 311
Discophora, 18, 42, 165, 346, 383
Distomeæ, 189, 205, 425
Distomum, 31
" cygnoides, 209
" globiparum, 207
" lanceolatum, 205
Dochmius duodenale, 375
" trigonocephalus, 375
Donacia, 401
Dracunculus, 376, 377
Echinaster fallax, 23
" Sarsii, 102, 561
Echinodermata, 5, 18, 24, 35, 74, 102, 325, 424, 544, 573, 574, 576, 582
Echinoidea, 35, 36, 544, 549, 565, 576
Echinorhyncus, 379, 380
Echinus lividus, 83, 84, 88
Echiurus, 44, 357, 358
Ectoprocta, 297, 306
Edriophthalmata, 459, 465
Elaphocaris, 473
Elasmobranchii, 23, 56, 59, 61, 62, 64, 67, 105, 106, 107, 108, 109
Enopla, 189, 202
Entoconcha mirabilis, 237
Entomophaga, 421
Entoprocta, 292, 298, 300, 302, 304, 306
Epeira, 436
Ephemera, 395, 409, 420, 422
Ephyra, 186
Epibulia aurantiaca, 159, 165
Erichthus, 484, 507
Errantia, 319, 336
Esperia, 147
Estheria, 463, 464
Euaxes, 101, 322, 324, 341, 346, 349
Eucharis, 178
" multicornis, 178
Eucopepoda, 459
Eucope polystyla, 23, 154
Eunice sanguinea, 319
Eupagurus prideauxii, 112, 113, 115, 511, 520
Euphausia, 465, 468, 504, 505, 518, 523
Eurostomata, 176
Eurylepta auriculata, 192
Eurynome, 483
Euspongia, 146, 147
Filaria, 377
Filaridæ, 371
Firoloidea, 240
Flagellata, 7, 8
Flustrella, 301, 303
Formica, 396
Fungia, 182, 186
Fusus, 275, 280, 284, 288
Gammarus, 122, 518
" fluviatilis, 117
" locusta, 110, 112
Ganoids, 54, 102
Gasteropoda, 39, 41, 98, 225, 226, 229, 230, 232, 233, 240, 258, 260, 261, 270, 272, 275, 279, 283, 324
Gasterosteus, 64, 210
Gastrotricha, 370
Gasterotrochæ, 330, 333
Gecarcinus, 465
Geophilus, 392, 393
Gephyrea, 5, 18, 24, 44, 54, 67, 102, 318, 320, 325, 355, 357, 361, 364
Germogen, 134
Geryonia hastata, 156
Geryonidæ, 156
Glochidia, 267, 268
Gnathobdellidæ, 346, 349
Gordiacea, 94
Gordioidea, 371, 374, 378
Gorgonia, 168
Gorgonidæ, 181
Gorgoninæ, 181
Gregarinidæ, 8
Gryllotalpa, 401, 412, 413
Gummineæ, 147, 148
Gymnoblastic Hydroids, 184, 185
Gymnolæmata, 292
Gymnosomata, 225, 240, 241, 242, 270
Gyrodactylus, 210
Halichondria, 147
Halisarca, 22, 66, 145
Halistemma, 165
Helicidæ, 238
Helioporidæ, 182
Helix, 67, 229
Hemiptera, 395, 402, 403, 409, 420, 421
Hessia, 108, 492
Heterakis vermicularis, 374
Heteronereis, 343
Heteropoda, 71, 72, 225, 226, 231, 278
Hexacoralla, 152, 179, 182
Hippopodius gleba, 27, 159
Hirudinea, 74, 84
Hirudo, 350, 351, 352, 353, 354
Holometabola, 420, 422
Holostomum, 205
Holothuria, 19, 25, 35, 549, 558, 576
Holothuroidea, 35, 544, 553, 556
Homarus, 477
Hyaleacea, 273, 275
Hyaleidæ, 241
Hydra, 21, 22, 26, 28, 29, 34, 152, 154, 155, 179, 183
Hydractinia, 539
Hydrocoralla, 152, 181, 185
Hydroidea, 152
Hydromedusæ, 152, 179, 182, 183, 184, 185, 186, 187
Hydrophilus, 374, 396, 400, 401, 402, 404, 408, 409
Hydrozoa, 14, 19, 26, 27, 67, 102, 152,155, 165, 179, 180, 181, 182, 539
Hymenoptera, 396, 401, 402, 412, 420, 421, 425
Ichneumon, 396
Inarticulata, 311, 316
Inermia, 355
Infusoria, 7, 8
Insecta, 5, 15, 18, 19, 25, 46, 395, 396, 425, 455, 458
Intoshia gigas, 136
Isidinæ, 181
Isodyctia, 147
Isopoda, 109, 515, 519, 521, 523, 527
Julus Moncletei, 387, 388, 389
Kochlorine, 499
Lacertilia, 64
Lacinularia, 221, 223
" socialis, 75
Lamellibranchiata, 23, 25, 37, 39, 98, 225, 241, 257, 258, 259, 269, 270, 271, 273, 274, 288
Lepadidæ, 498
Lepas fascicularis, 224, 493, 494, 495
Lepidoptera, 79, 396, 402, 407, 408, 412, 413, 415, 417, 420, 421, 423, 425, 426, 455
Leptodora, 16, 51
Leptoplana, 74, 189, 192, 193
Lernæopoda, 490, 492, 520
Leucifer, 507
Libellulidæ, 402, 403, 409, 420
Limax, 229, 232, 239, 278, 280
Limnadia, 79, 524
Limulus, 534
Lina, 402
Lingulidæ, 311, 316
Lithobius, 393
Lobatæ, 178
Loligo, 242, 243, 244, 247, 253
Loricata, 507, 514
Lota, 105
Loxosoma, 292, 294, 296, 306, 307
Lucernaria, 185
Lumbricus, 341, 368
" agricola, 321
" rubellus, 324
" trapezoides, 13, 321, 323
Lumbriconereis, 334
Lymnæus, 82, 98, 226, 227, 232, 238, 281
Lycosa, 436
Macrostomum, 32, 34
Macrura, 476
Malacobdella, 203
Malacodermata, 171
Malacostraca, 66, 459, 462, 465, 504, 505, 506, 511, 523
Mammalia, 56, 58, 59, 64, 66
Marsipobranchii, 59
Mastigopus, 473, 474
Medusæ, 27, 154, 157, 158, 163, 164, 176, 178, 181, 182, 183, 184, 185, 186
Megalopa, 482, 483, 484
Melolontha, 402, 421
Membranipora, 297, 303
Mermithidæ, 371
Mesotrochæ, 330
Metachætæ, 335
Metazoa, 9, 10, 12, 67, 86, 125, 135, 149, 150, 179
Millepora, 152, 181
Mitraria, 308, 337
Molgula, 102
Mollusca, 5, 18, 24, 66, 74, 84, 99, 225, 247, 248, 251, 256, 257, 262, 271, 285, 288, 307, 325, 333, 352, 576, 582
Monomya, 225
Monostomum capitellum, 205
" mutabile, 205, 206
Monotrochæ, 330
Montacuta, 260, 262
Musca, 396
Muscidæ, 420, 423
Myobia, 444, 445
Myrianida, 343
Myriapoda, 22, 111, 113, 387, 394, 395, 413, 458
Myriothela, 155
Myrmeleon, 396
Mysis, 120, 469, 472, 486, 504, 509, 525
Mytilus, 260, 261
Myxinoids, 5
Myxispongiæ, 145
Myzostomea, 369
Nais, 342
Nassa mutabilis, 101, 226, 227, 233, 262, 278, 279, 288, 324
Natantia, 487
Natica, 237, 283
Nauplius, 5, 16, 460, 461, 463, 465, 466, 469, 473, 490, 491, 493, 497
Nautilus pompilius, 253, 276
Nebaliadæ, 459, 465, 486
Nematoda, 45, 46, 50, 66, 74, 75, 371, 373, 374, 376
Nematogens, 131
Nematoidea, 18, 84, 94, 371, 374
Nematus ventricosus, 13, 427
Nemertea, 94, 189, 196, 202, 204
Nemertines, 30, 31, 33, 93, 136, 195, 202, 328, 333, 424
Nephelis, 82, 346, 349, 350, 351, 352, 354
Nereis, 343
" diversicolor, 319
" Dumerilii, 343
Neritina, 229, 237
Neuroptera, 396, 401, 420, 421
Neuroterus ventricularis, 428
Notonecta, 395
Nototrochæ, 330, 353
Nudibranchiata, 229, 241
Ocellata, 184
Octocoralla, 152, 179
Octopus, 248
Odontophora, 225, 257, 271
Odontosyllis, 333
Oedogonium, 11
Oligochæta, 42, 319, 321, 325, 330, 338, 346, 352
Olynthus, 144
Oniscus murarius, 107, 108, 109, 120, 516, 520, 528
Opercula, 31
Ophiothryx, 36, 549
Ophidia, 64
Ophiuroidea, 136, 544, 553, 562, 565, 576
Ophryotrochæ puerilis, 333
Opisthobranchiata, 225, 232, 237
Ornithodelphia, 109
Orthonectidæ, 136
Orthoptera, 395, 414, 420, 421, 425, 426
Ostracoda, 459, 500, 510
Ostrea, 259, 260, 262
Oxyuridæ, 46, 373, 374
Oxyurus ambigua, 374
" vermicularis, 375
Pæcilopoda, 534
Paguridæ, 477
Palæmon, 110
Palæmonetes, 476
Palæmoninæ, 476, 511, 512
Palinurus, 478, 480
Paludina, 66, 227, 229, 235, 270, 278, 280
" costata, 229
" vivipara, 226
Pandorina, 11
Parasita, 489
Pedalion, 221
Pedicellina, 98, 292, 296, 299, 307
Pelagia, 167, 185
Penæinæ, 476
Penæus, 110, 113, 465, 469, 473, 474, 504, 518
Pennatulidæ, 181
Pentacrinus, 5
Pentastomida, 539, 540
Pentastomum denticulatum, 540, 541
" tænoides, 539, 540, 541
Percidæ, 64
Perennichætæ, 335
Peripatus, 5, 386, 411, 412, 413, 542
Petromyzon, 61, 63, 64, 74, 83
Phalangella, 304
Phalangidæ, 436
Phallusia, 83
Phascolosoma, 44, 355, 356, 361
Pholcus, 436, 442
Phoronis, 315, 355, 363, 364
Phoxinus lævis, 378
Phryganea, 396, 401, 409
Phylactolæmata, 292, 294, 297, 305, 306
Phyllobothrium, 218
Phyllodoce, 329
Phyllopoda, 16, 459, 461, 505
Phyllosoma, 479, 480
Phylloxera, 429
Physophoridæ, 152, 162, 164
Pilidium, type of, 196, 200, 201, 202, 204, 424
Pisces, 5
Piscicola, 20, 43
Pisidium, 259, 260, 262, 264
Planaria Neapolitana, 193
Planorbis, 273, 281, 325
Platyelminthes, 18, 20, 24, 221, 424
Platygaster, 396, 416, 417, 418, 419
Pleurobrachia, 176, 177, 238
Pneumodermon, 242, 576
Podostomata, 292
Poduridæ, 401, 405
Polychæta, 42, 319, 325, 338
Polydesmus complanatus, 387, 388
Polygordius, 319, 325, 326, 327, 328, 332, 357, 386
Polynoe, 42, 331
Polyophthalmus, 328
Polyplacophora, 225, 254, 270, 271, 288
Polystomeæ, 189, 205, 209
Polystomum, 209
" integerrimum, 30, 31, 210
Polytrochæ, 330, 333
Polyxenia leucostyla, 158
Polyxenus lagurus, 387
Polyzoa, 98, 303, 305, 306, 308, 315, 316
Porcellana, 483
Porifera, 102, 138, 148
Porthesia, 115
Prorhyncus, 32, 34
Prosobranchiata, 225, 237, 281
Prostomum, 32, 34, 38, 196
Protozoa, 8, 9, 10, 11, 86, 135, 149
Protozoæa, 471
Protula Dysteri, 342
Pseudoneuroptera, 426
Pseudoscorpionidæ, 434
Psolinus, 556, 574
Psychidæ, 16
Pteraster miliaris, 561
Pteropoda, 98, 225, 226, 229, 230, 232, 240, 258, 270, 272, 279, 283
Pterotrachæa, 71, 229, 240
Pulex, 396
Pulmonata, 39, 225, 232, 238, 281, 282
Purpura lapillus, 78
Pycnogonida, 538
Pyrosoma, 13, 53, 109
Rana temporaria, 210
Raspailia, 147
Redia, 206, 207, 208, 209
Reniera, 147
Reptilia, 56, 59, 60, 61, 62, 64, 109
Rhabditis dolichura, 82
Rhabdocoela, 32, 33, 189, 196
Rhabdopleura, 294, 306
Rhizocephala, 459, 493, 499, 500
Rhizocrinus, 5
Rhizostoma, 167
Rhombogens, 131, 134
Rhynchonellidæ, 311
Rhyncobdellidæ, 346
Rotifera, 5, 12, 18, 75, 76, 77, 79, 83, 102, 221, 308, 325
Saccocirrus, 328, 329, 332, 340
Sacculina, 500
Sagartia, 169, 171
Sagitta, 23, 74, 94, 130, 366, 367, 368
Salmonidæ, 64
Salpa, 102
Sarcia, 164
Scaphopoda, 225, 257, 270, 271
Schistocephalus, 211
Schizopoda, 459, 465, 466
Scolopendra, 392
Scorpio, 120, 431, 446, 454, 455, 457
Scrobicularia, 38, 39
Scyllarus, 477
Scyphistoma, 179, 185, 186
Sedentaria, 319, 336
Sepia, 20, 40, 41, 242, 243, 244, 245, 247, 249, 253
Sergestidæ, 473, 507
Serpula, 319, 325, 331
Sertularia, 152, 183, 184
Silicispongiæ, 147
Simulia, 401, 415
Siphonophora, 13, 27, 152, 159, 163, 165, 179, 180, 182, 185
Sipunculida, 24
Sipunculus, 44
Sirex, 396
Sitaris, 421
Spathegaster baccarum, 428
Spio, 42, 332, 333
Spiroptera obtusa, 376
Spirorbis Pagenstecheri, 319
" spirillum, 319, 336
Spirula, 252
Spirulirostra, 252
Spongelia, 147
Spongida, 138, 144, 148, 149
Spongilla, 147, 150
Sporocysts, 206, 207, 208, 209
Squilla, 66, 504, 507
Stephanomia pictum, 162, 165
Stomatopoda, 459, 465, 484
Stomodæum, 413
Strongylidæ, 371, 375
Strongylocentrus, 567
Strongysoloma Guerinii, 387, 388, 390
Stylasteridæ, 152, 181
Styliolidæ, 241
Stylochopsis ponticus, 193
Sycandra, 93, 138, 144, 145, 147, 150
" raphanus, 138, 174
Syllis, 343
" vivipara, 319
Sympodium coralloides, 168
Tæniatæ, 178
Tardigrada, 541
Tegenaria, 436
Teleostei, 18, 25, 56, 59, 64, 107, 109
Telotrochæ, 330
Tendra, 300
Tenthreds, 396
Terebella conchilega, 332, 333, 337
Terebella nebulosa, 332, 333
Terebratula, 311, 315
Terebratulina, 311, 315, 316
" septentrionalis, 315, 316
Teredo, larva of, 262
Tergipes, 232, 238
" Edwardsii, 238
" lacinulatus, 238
Tethya, 147
Tetrabranchiata, 225
Tetranychus telarius, 116
Tetrastemma varicolor, 203
Thalassema, 44, 355, 357
Thalassinidæ, 477
Thallophytes, 11
Thecidium, 311, 312, 315, 316
Thecosomata, 225
Thoracica, 459, 493, 499, 500
Thysanozoon, 192, 193
Thysanura, 395, 408, 425, 458
Tichogonia, 39
Tipula, 396
Tipulidæ, 420, 421
Toenia coenurus, 214
" echinococcus, 215, 217
" solium, 217
Tornaria, 579, 581
Toxopneustes, 22, 24, 35, 85, 88, 89
Tracheata, 385, 426, 432, 448, 455, 457, 458, 538, 541
Trachymedusæ, 152, 156, 179, 185
Trematodes, 14, 16, 29, 30, 31, 32, 33, 46, 94, 189, 205, 208, 210, 212, 216
Trichina, 377, 378
Trichinidæ, 371
Trichocephalus affinis, 374
Trochosphæra æquatorialis, 221
Tubiporidæ, 182
Tubularia, 34, 38, 152, 154, 158
Tubularidæ, 29, 179, 183
Tunicata, 5, 14, 53
Turbellaria, 5, 30, 31, 33, 74, 98, 102, 136, 179, 189, 193, 333
Tyroglyphus, 445
Unio, 37, 38, 39, 100, 101, 259, 260, 265, 266, 445
Vaginulus luzonicus, 229
Vermes, 5, 74, 102, 223, 324, 352
Verongia rosea, 146
Vertebrata, 14, 18, 19, 24, 59, 64, 83, 272, 349, 397, 426
Vesiculata, 184
Vitrina, 229
Vorticella, 8, 9, 10
Wilsia, 164
Xiphoteuthis, 252
Zoantharia, 152, 168, 169
Zoæa, 465, 468, 471, 474, 482, 483, 484, 486, 504
BIBLIOGRAPHY.
THE OVUM.
General Works.
(1) Ed. van Beneden. "Recherches sur la composition et la signification de l'oeuf," etc. Mém. cour. d. l'Acad. roy. des Sciences de Belgique, Vol. XXXIV. 1870.
(2) R. Leuckart. Artikel "Zeugung," R. Wagner's Handwörterbuch d. Physiologie, Vol. IV. 1853.
(3) Fr. Leydig. "Die Dotterfurchung nach ihrem Vorkommen in d. Thierwelt u. n. ihrer Bedeutung." Oken. Isis, 1848.
(4) Ludwig. "Ueber d. Eibildung im Thierreiche." Arbeiten a. d. zool.-zoot. Institut. Würzburg, Vol. I. 1874[231].
(5) Allen Thomson. Article "Ovum" in Todd's Cyclopædia of Anatomy and Physiology, Vol. V. 1859.
(6) W. Waldeyer. Eierstock u. Ei. Leipzig, 1870.
[231] A very complete and critical account of the literature is contained in this paper.
THE OVUM OF COELENTERATA.
(7) Ed. van Beneden. "De la distinction originelle d. testicule et de l'ovaire." Bull. Acad. roy. Belgique, 3e série, Vol. XXXVII. 1874.
(8) R. and O. Hertwig. Der Organismus d. Medusen. Jena, 1878.
(9) N. Kleinenberg. Hydra. Leipzig, 1872.
THE OVUM OF PLATYELMINTHES.
(10) P. Hallez. Contributions à l'Histoire naturelle des Turbellariés. Lille, 1879.
(11) S. Max Schultze. Beiträge z. Naturgeschichte d. Turbellarien. Greifswald, 1851.
(12) C. Th. von Siebold. "Helminthologische Beiträge." Müller's Archiv, 1836.
(13) C. Th. von Siebold. Lehrbuch d. vergleich. Anat. d. wirbellosen Thiere. Berlin, 1848.
(14) E. Zeller. "Weitere Beiträge z. Kenntniss d. Polystomen." Zeit. f. wiss. Zool., Bd. XXVII. 1876.
[Vide also Ed. van Beneden (No. 1).]
THE OVUM OF ECHINODERMATA.
(15) C. K. Hoffmann. "Zur Anatomie d. Echiniden u. Spatangen." Niederländisch. Archiv f. Zoologie, Vol. I. 1871.
(16) C. K. Hoffmann. "Zur Anatomie d. Asteriden." Niederländisch. Archiv f. Zoologie, Vol. II. 1873.
(17) H. Ludwig. "Beiträge zur Anat. d. Crinoiden." Zeit. f. wiss. Zool., Vol. XXVIII. 1877.
(18) Joh. Müller. "Ueber d. Canal in d. Eiern d. Holothurien." Müller's Archiv, 1854.
(19) C. Semper. Holothurien. Leipzig, 1868.
(20) E. Selenka. Befruchtung d. Eies v. Toxopneustes variegatus, 1878.
[Vide also Ludwig (No. 4), etc.]
THE OVUM OF MOLLUSCA.
Lamellibranchiata.
(21) H. Lacaze-Duthiers. "Organes génitaux des Acéphales Lamellibranches." Ann. Sci. Nat., 4me série, Vol. II. 1854.
(22) W. Flemming. "Ueb. d. er. Entwick. am Ei d. Teichmuschel." Archiv f. mikr. Anat., Vol. X. 1874.
(23) W. Flemming. "Studien üb. d. Entwick. d. Najaden." Sitz. d. k. Akad. Wiss. Wien, Vol. LXXI. 1875.
(24) Th. von Hessling. "Einige Bemerkungen, etc." Zeit. f. wiss. Zool., Bd. V. 1854.
(25) H. von Jhering. "Zur Kenntniss d. Eibildung bei d. Muscheln." Zeit. f. wiss. Zool., Vol. XXIX. 1877.
(26) Keber. De Introitu Spermatozoorum in ovula, etc. Königsberg, 1853.
(27) Fr. Leydig. "Kleinere Mittheilung etc." Müller's Archiv, 1854.
Gasteropoda.
(28) C. Semper. "Beiträge z. Anat. u. Physiol. d. Pulmonaten." Zeit. f. wiss. Zool., Vol. VIII. 1857.
(29) H. Eisig. "Beiträge z. Anat. u. Entwick. d. Pulmonaten." Zeit. f. wiss. Zool., Vol. XIX. 1869.
(30) Fr. Leydig. "Ueb. Paludina vivipara." Zeit. f. wiss. Zool., Vol. II. 1850.
Cephalopoda.
(31) Al. Kölliker. Entwicklungsgeschichte d. Cephalopoden. Zürich, 1844.
(32) E. R. Lankester. "On the Developmental History of the Mollusca." Phil. Trans., 1875.
THE OVUM OF THE CHÆTOPODA.
(33) Ed. Claparède. "Les Annelides Chætopodes d. Golfe de Naples." Mém. d. l. Sociét. phys. et d'hist. nat. de Genève, 1868-9 and 1870.
(34) E. Ehlers. Die Borstenwürmer nach system. und anat. Untersuchungen. Leipzig, 1864-68.
(35) E. Selenka. "Das Gefäss-System d. Aphrodite aculeata." Niederländisches Archiv f. Zool., Vol. II. 1873.
THE OVUM OF DISCOPHORA.
(36) H. Dorner. "Ueber d. Gattung Branchiobdella." Zeit. f. wiss. Zool., Vol. XV. 1865.
(37) R. Leuckart. Die menschlichen Parasiten.
(38) Fr. Leydig. "Zur Anatomie v. Piscicola geometrica, etc." Zeit. f. wiss. Zool., Vol. I. 1849.
(39) C. O. Whitman. "Embryology of Clepsine." Quart. J. of Micr. Sci., Vol. XVIII. 1878.
THE OVUM OF GEPHYREA.
(40) Keferstein u. Ehlers. Zoologische Beiträge. Leipzig, 1861.
(41) C. Semper. Holothurien, 1868, p. 145.
(42) J. W. Spengel. "Beiträge z. Kenntniss d. Gephyreen." Beiträge a. d. zool. Station z. Neapel, Vol. I. 1879.
(43) J. W. Spengel. "Anatomische Mittheilungen üb. Gephyreen." Tagebl. d. Naturf. Vers. München, 1877.
THE OVUM OF NEMATODA.
(44) Ed. Claparède. De la formation et de la fécondation des oeufs chez les Vers Nématodes. Genève, 1859.
(45) R. Leuckart. Die menschlichen Parasiten. (46) H. Munk. "Ueb. Ei- u. Samenbildung u. Befruchtung b. d. Nematoden." _Zeit. f. wiss. Zool._, Vol. IX. 1858.
(47) H. Nelson. "On the reproduction of Ascaris mystax, etc." Phil. Trans. 1852.
(48) A. Schneider. Monographie d. Nematoden. Berlin, 1866.
THE OVUM OF INSECTA.
(49) A. Brandt. Ueber das Ei u. seine Bildungsstätte. Leipzig, 1878.
(50) T. H. Huxley. "On the agamic reproduction and morphology of Aphis." Linnean Trans., Vol. XXII. 1858. Vide also Manual of Invertebrated Animals, 1877.
(51) R. Leuckart. "Ueber die Micropyle u. den feinern Bau d. Schalenhaut bei den Insecteneiern." Müller's Archiv, 1855.
(52) Fr. Leydig. Der Eierstock u. die Samentasche d. Insecten. Dresden, 1866.
(53) Lubbock. "The ova and pseudova of Insects." Phil. Trans. 1859.
(54) Stein. Die weiblichen Geschlechtsorgane d. Käfer. Berlin, 1847.
[Conf. also Claus, Landois, Weismann, Ludwig (No. 4).]
THE OVUM OF ARANEINA.
(55) Victor Carus. "Ueb. d. Entwick. d. Spinneneies." Zeit. f. wiss. Zool., Vol. II. 1850.
(56) v. Wittich. "Die Entstehung d. Arachnideneies im Eierstock, etc." Müller's Archiv, 1849.
[Conf. Leydig, Balbiani, Ludwig (No. 4), etc.]
THE OVUM OF CRUSTACEA.
(57) Aug. Weismann. "Ueb. d. Bildung von Wintereiern bei Leptodora hyalina." Zeit. f. wiss. Zool., Vol. XXVII. 1876.
[For general literature vide Ludwig, No. 4, and Ed. van Beneden, No. 1.]
THE OVUM OF CHORDATA.
Urochorda (Tunicata).
(58) A. Kowalevsky. "Weitere Studien ü. d. Entwicklung d. Ascidien." Archiv f. mikr. Anat., Vol. VII. 1871.
(59) A. Kowalevsky. "Ueber Entwicklungsgeschichte d. Pyrosoma." Arch. f. mikr. Anat., Vol. XI. 1875.
(60) Kupffer. "Stammverwandtschaft zwischen Ascidien u. Wirbelthieren." Arch. f. mikr. Anat., Vol. VI. 1870.
(61) Giard. "Études critiques des travaux, etc." Archives Zool. expériment., Vol. I. 1872.
(62) C. Semper. "Ueber die Entstehung, etc." Arbeiten a. d. zool.-zoot. Institut Würzburg, Bd. II. 1875.
Cephalochorda.
(63) P. Langerhans. "Z. Anatomie d. Amphioxus lanceolatus," pp. 330-3. Archiv f. mikr. Anat., Vol. XII. 1876.
Craniata.
(64) F. M. Balfour. "On the structure and development of the Vertebrate Ovary." Quart. J. of Micr. Science, Vol. XVIII. 1878.
(65) Th. Eimer. "Untersuchungen ü. d. Eier d. Reptilien." Archiv f. mikr. Anat., Vol. VIII. 1872.
(66) Pflüger. Die Eierstöcke d. Säugethiere u. d. Menschen. Leipzig, 1863.
(67) J. Foulis. "On the development of the ova and structure of the ovary in Man and other Mammalia." Quart. J. of Micr. Science, Vol. XVI. 1876.
(68) J. Foulis. "The development of the ova, etc." Journal of Anat. and Phys., Vol. XIII. 1878-9.
(69) C. Gegenbaur. "Ueb. d. Bau u. d. Entwicklung d. Wirbelthiereier mit partieller Dottertheilung." Müller's Archiv, 1861.
(70) Alex. Götte. Entwicklungsgeschichte d. Unke. Leipzig, 1875.
(71) W. His. Untersuchungen üb. d. Ei u. d. Eientwicklung bei Knochenfischen. Leipzig, 1873.
(72) A. Kölliker. Entwicklungsgeschichte d. Menschen u. höherer Thiere. Leipzig, 1878.
(73) J. Müller. "Ueber d. zahlreichen Porenkanäle in d. Eikapsel d. Fische." Müller's Archiv, 1854.
(74) W. H. Ransom. "On the impregnation of the ovum in the Stickleback." Pro. R. Society, Vol. VII. 1854.
(75) C. Semper. "Das Urogenitalsystem d. Plagiostomen etc." Arbeiten a. d. zool.-zoot. Instit. Würzburg, Vol. II. 1875.
[Cf. Ludwig, No. 4, Ed. van Beneden, No. 1, Waldeyer, No. 6, etc.]
MATURATION AND IMPREGNATION OF THE OVUM.
(76) Auerbach. Organologische Studien, Heft 2. Breslau, 1874.
(77) Bambeke. "Recherches s. Embryologie des Batraciens." Bull. de l'Acad. royale de Belgique, 2me sér., T. LXI. 1876.
(78) E. van Beneden. "La Maturation de l'OEuf des Mammifères." Bull. de l'Acad. royale de Belgique, 2me sér., T. XL. No. 12, 1875.
(79) Idem. "Contributions à l'Histoire de la Vésicule Germinative, &c." Bull. de l'Acad. royale de Belgique, 2me sér., T. XLI. No. 1, 1876.
(80) O. Bütschli. Eizelle, Zelltheilung, und Conjugation der Infusorien. Frankfurt, 1876.
(81) F. M. Balfour. "On the Phenomena accompanying the Maturation and Impregnation of the Ovum." Quart. J. of Micros. Science, Vol. XVIII. 1878.
(82) Calberla. "Befruchtungsvorgang beim Ei von Petromyzon Planeri." Zeit. f. wiss. Zool., Vol. XXX.
(83) W. Flemming. "Studien in d. Entwickelungsgeschichte der Najaden." Sitz. d. k. Akad. Wien, B. LXXI. 1875.
(84) H. Fol. "Die erste Entwickelung des Geryonideneies." Jenaische Zeitschrift, Vol. VII. 1873.
(85) Idem. "Sur le Développement des Ptéropodes." Archives de Zoologie Expérimentale et Générale, Vol. IV. and V. 1875-6.
(86) Idem. "Sur le Commencement de l'Hénogénie." Archives des Sciences Physiques et Naturelles. Genève, 1877.
(87) Idem. Recherches s. l. Fécondation et l. commen. d. l'Hénogénie. Genève, 1879.
(88) R. Greeff. "Ueb. d. Bau u. d. Entwickelung d. Echinodermen." _Sitzun. der Gesellschaft z. Beförderung d. gesammten Naturwiss. z. Marburg_, No. 5, 1876.
(89) Oscar Hertwig. "Beit. z. Kenntniss d. Bildung, &c., d. thier. Eies." Morphologisches Jahrbuch, Vol. I. 1876.
(90) Idem. Ibid. Morphologisches Jahrbuch, Vol. III. Heft 1, 1877.
(91) Idem. "Weitere Beiträge, &c." Morphologisches Jahrbuch, Vol. III. 1877. Heft 3.
(92) Idem. "Beit. z. Kenntniss, &c." Morphologisches Jahrbuch, Vol. IV. Heft 1 and 2. 1878.
(93) N. Kleinenberg. Hydra. Leipzig, 1872.
(94) C. Kupffer u. B. Benecke. Der Vorgang d. Befruchtung am Eie d. Neunaugen. Königsberg, 1878.
(95) J. Oellacher. "Beiträge zur Geschichte des Keimbläschens im Wirbelthiere." Archiv f. mikr. Anat., Bd. VIII. 1872.
(96) W. Salensky. "Befruchtung u. Furchung d. Sterlets-Eies." Zoologischer Anzeiger, No. 11, 1878.
(97) E. Selenka. Befruchtung des Eies von Toxopneustes variegatus. Leipzig, 1878.
(98) Strasburger. Ueber Zellbildung u. Zelltheilung. Jena, 1876.
(99) Idem. Ueber Befruchtung u. Zelltheilung. Jena, 1878.
(100) C. O. Whitman. "The Embryology of Clepsine." Quart. J. of Micr. Science, Vol. XVIII. 1878.
DIVISION OF NUCLEUS.
(101) W. Flemming. "Beiträge z. Kenntniss d. Zelle u. ihrer Lebenserscheinungen." Archiv f. mikr. Anat., Vol. XVI. 1878.
(102) E. Klein. "Observations on the glandular epithelium and division of nuclei in the skin of the Newt." Quart. J. of Micr. Science, Vol. XIX. 1879.
(103) Peremeschko. "Ueber d. Theilung d. thierischen Zellen." Archiv f. mikr. Anat., Vol. XVI. 1878.
(104) E. Strasburger. "Ueber ein z. Demonstration geeignetes Zelltheilungs-Object." Sitz. d. Jenaischen Gesell. f. Med. u. Naturwiss., July 18, 1879.
SEGMENTATION.
(105) E. Haeckel. "Die Gastrula u. Eifurchung." Jenaische Zeitschrift, Vol. IX. 1877.
(106) Fr. Leydig. "Die Dotterfurchung nach ihrem Vorkommen in d. Thierwelt u. n. ihrer Bedeutung." Oken. Isis. 1848.
GENERAL WORKS ON EMBRYOLOGY.
(107) K. E. von Baer. "Ueb. Entwicklungsgeschichte d. Thiere." Königsberg, 1828-37.
(108) C. Claus. Grundzüge d. Zoologie. Marburg und Leipzig, 1879.
(109) C. Gegenbaur. Grundriss d. vergleichenden Anatomie. Leipzig, 1878. Vide also Translation. Elements of Comparative Anatomy. Macmillan and Co., 1878.
(110) E. Haeckel. Studien z. Gastræa-Theorie. Jena, 1877, and also Jenaische Zeitschrift, Vols. VIII. and IX.
(111) E. Haeckel. Schöpfungsgeschichte. Leipzig. Vide also Translation. The History of Creation. King and Co., London, 1876.
(112) E. Haeckel. Anthropogenie. Leipzig. Vide also Translation. Anthropogeny (Translation). Kegan Paul and Co., London, 1878.
(113) Th. H. Huxley. The Anatomy of Invertebrated Animals. Churchill, 1877.
(114) E. R. Lankester. "Notes on Embryology and Classification." Quart. J. of Micr. Science, Vol. XVII. 1877.
(115) A. S. P. Packard. Life Histories of Animals, including Man, or Outlines of Comparative Embryology. Holt and Co., New York, 1876.
(116) H. Rathke. Abhandlungen z. Bildung- und Entwicklungsgesch. d. Menschen u. d. Thiere. Leipzig, 1833.
DICYEMIDÆ.
(117) E. van Beneden. "Recherches sur les Dicyemides." Bull. d. l'Académie roy. de Belgique, 2e sér. T. XLI. No. 6 and T. XLII. No. 7, 1876. Vide this paper for a full account of the literature.
(118) A. Kölliker. Ueber Dicyema paradoxum den Schmarotzer der Venenanhänge der Cephalopoden.
(119) Aug. Krohn. "Ueb. d. Vorkommen von Entozoen, etc." Froriep Notizen, VII. 1839.
ORTHONECTIDÆ.
(120) Alf. Giard. "Les Orthonectida classe nouv. d. Phylum des Vers." Journal de l'Anat. et de la Physiol., Vol. XV. 1879.
(121) El. Metschnikoff. "Zur Naturgeschichte d. Orthonectidæ." Zoologischer Anzeiger, No. 40-43, 1879.
PORIFERA.
(122) C. Barrois. "Embryologie de quelques éponges de la Manche." Annales des Sc. Nat. Zool., VI. ser., Vol. III. 1876.
(123) Carter. "Development of the marine Sponges." Annals and Mag. of Nat. Hist., 4th series, Vol. XIV. 1874.
(124) Ganin[232]. "Zur Entwicklung d. Spongilla fluviatilis." Zoologischer Anzeiger, Vol. I. No. 9, 1878.
(125) Robert Grant. "Observations and Experiments on the Structure and Functions of the Sponge." Edinburgh Phil. J., Vol. XIII. and XIV., 1825, 1826.
(126) E. Haeckel. Die Kalkschwämme, 1872.
(127) E. Haeckel. Studien zur Gastræa-Theorie. Jena, 1877.
(128) C. Keller. Untersuchungen über Anatomie und Entwicklungsgeschichte einiger Spongien. Basel, 1876.
(129) C. Keller. "Studien üb. Organisation u. Entwick. d. Chalineen." Zeit. f. wiss. Zool., Bd. XXVIII. 1879.
(130) Lieberkühn. "Beitr. z. Entwick. d. Spongillen." Müller's Archiv, 1856.
(131) Lieberkühn. "Neue Beiträge zur Anatomie der Spongien." Müller's Archiv, 1859.
(132) El. Metschnikoff. "Zur Entwicklungsgeschichte der Kalkschwämme." Zeit. f. wiss. Zool., Bd. XXIV. 1874.
(133) El. Metschnikoff. "Beiträge zur Morphologie der Spongien." ZEIT. F. WISS. ZOOL., Bd. XXVII. 1876.
(134) El. Metschnikoff. "Spongeologische Studien." Zeit. f wiss. Zool., Bd. XXXII. 1879.
(135) Miklucho-Maklay.. "Beiträge zur Kenntniss der Spongien." Jenaische Zeitschrift, Bd. IV. 1868.
(136) O. Schmidt. "Zur Orientirung über die Entwicklung der Schwämme." Zeit. f. wiss. Zool., Bd. XXV. 1875.
(137) O. Schmidt. "Nochmals die Gastrula der Kalkschwämme." Archiv für mikrosk. Anat., Bd. XII. 1876.
(138) O. Schmidt. "Das Larvenstadium von Ascetta primordialis und Asc. clathrus." Archiv für mikrosk. Anatomie, Bd. XIV. 1877.
(139) F. E. Schulze. "Ueber den Bau und die Entwicklung von Sycandra raphanus." Zeit. f. wiss. Zool., Bd. XXV. 1875.
(140) F. E. Schulze. "Zur Entwicklungsgeschichte von Sycandra." Zeit. f wiss. Zool., Bd. XXVII. 1876.
(141) F. E. Schulze. "Untersuchung üb. d. Bau, etc. Die Gattung Halisarca." Zeit. f. wiss. Zool., Bd. XXVIII. 1877.
(142) F. E. Schulze. "Untersuchungen üb. d. Bau, etc. Die Metamorphose von Sycandra raphanus." Zeit. f. wiss. Zool., Bd. XXXI. 1878.
(143) F. E. Schulze. "Untersuchungen ü. d. Bau, etc. Die Familie Aplysinidæ." Zeit. f. wiss. Zool., Bd. XXX. 1878.
(144) F. E. Schulze. "Untersuchungen ü. d. Bau, etc. Die Gattung Spongelia." Zeit. f. wiss. Zool., Bd. XXXII. 1878.
[232] There is a Russian paper by the same author, containing a full account, with clear illustrations, of his observations.
COELENTERATA.
General.
(145) Alex. Agassiz. Illustrated Catalogue of the Museum of Comparative Anatomy at Harvard College, No. II. American Acalephæ. Cambridge, U. S., 1865.
(146) O. and R. Hertwig. Der Organismus d. Medusæ u. seine Stellung z. Keimblattertheorie. Jena, 1878.
(147) A. Kowalevsky. "Untersuchungen üb. d. Entwicklung d. Coelenteraten." _Nachrichten d. kaiser. Gesell. d. Freunde d. Naturerkenntniss d. Anthropologie u. Ethnographie._ Moskau, 1873. (Russian). For abstract vide Jahresberichte d. Anat. u. Phys. (Hoffman u. Schwalbe), 1873.
Hydrozoa.
(148) L. Agassiz. Contributions to the Natural History of the United States of America. Boston, 1862. Vol. IV.
(149) G. J. Allman. A Monograph of the Gymnoblastic or Tubularian Hydroids. Ray Society, 1871-2.
(150) G. J. Allman. "On the structure and development of Myriothela." Phil. Trans., Vol. CLXV. p. 2.
(151) P. J. van Beneden. "Mém. sur les Campanulaires de la Côte d'Ostende considérés sous le rapport physiologique, embryogénique, et zoologique." Nouv. Mém. de l'Acad. de Brux., Tom. XVII. 1844.
(152) P. J. van Beneden. "Recherches sur l'Embryogénic des Tubulaires et l'histoire naturelle des différents genres de cette famille qui habitent la Côte d'Ostende." Nouv. Mém. de l'Acad de Brux., Tom. XVII. 1844.
(153) C. Claus. "Polypen u. Quallen d. Adria." Denk. d. math.-naturwiss. Classe d. k. k. Akad. d. Wiss. Wien, Vol. XXXVIII. 1877.
(154) J. G. Dalyell. Rare and Remarkable Animals of Scotland. London, 1847.
(155) H. Fol. "Die erste Entwicklung d. Geryonideneies." Jenaische Zeitschrift, Vol. VII. 1873.
(156) Carl Gegenbaur. Zur Lehre vom Generationswechsel und der Fortpflanzung bei Medusen und Polypen. Würzburg, 1854.
(157) Thomas Hincks. "On the development of the Hydroid Polypes, Clavatella and Stauridia; with remarks on the relation between the Polype and the Medusoid, and between the Polype and the Medusa." Brit. Assoc. Rep., 1861.
(158) E. Haeckel. Zur Entwicklungsgeschichte d. Siphonophoren. Utrecht, 1869.
(159) Th. H. Huxley. Oceanic Hydrozoa. Ray Society, 1858.
(160) Geo. Johnston. A History of British Zoophytes. Edin. 1838. 2nd Edition, 1847.
(161) N. Kleinenberg. Hydra, eine anatomisch-entwicklungsgeschichtliche Untersuchung. Leipzig, 1872.
(162) El. Metschnikoff. "Ueber die Entwicklung einiger Coelenteraten." Bull. de l'Acad. de St Pétersbourg, XV. 1870.
(163) El. Metschnikoff. "Studien über Entwicklungsgeschichte d. Medusen u. Siphonophoren." Zeit. f. wiss. Zool., Bd. XXIV. 1874.
(164) H. N. Moseley. "On the structure of the Stylasteridæ." Phil. Trans., 1878.
(165) F. E. Schulze. Ueber den Bau und die Entwicklung von Cordylophora lacustris. Leipzig, 1871.
Actinozoa.
(166) Al. Agassiz. "Arachnitis (Edwarsia) brachiolata." Proc. Boston Nat. Hist. Society, 1860.
(167) Koch. "Das Skelet d. Alcyonarien." Morpholog. Jahrbuch, Bd. IV. 1878.
(168) A. Kowalevsky. "Z. Entwicklung d. Aleyoniden, Sympodium coralloides und Clavularia crassa." Zoologischer Anzeiger, No. 38, 1879.
(169) H. Lacaze Duthiers. Histoire nat. du Corail. Paris, 1864.
(170) H. Lacaze Duthiers. "Développement des Coralliaires." Archives de Zoologie expérimentale et générale, Vol. I. 1872 and Vol. II. 1873.
(171) C. Semper. "Ueber Generationswechsel bei Steinkorallen etc." Zeit. f. wiss. Zool., Bd. XXII. 1872.
Ctenophora.
(172) Alex. Agassiz. "Embryology of the Ctenophoræ." Mem. of the Amer. Acad. of Arts and Sciences, Vol. X. No. III. 1874.
(173) G. J. Allman. "Contributions to our knowledge of the structure and development of the Beroidæ." Proc. Roy. Soc. Edinburgh, Vol. IV. 1862.
(174) C. Chun. "Das Nervensystem u. die Musculatur d. Rippenquallen." Abhand. d. Senkenberg. Gesellsch., B. XI. 1879.
(175) C. Claus. "Bemerkungen ü. Ctenophoren u. Medusen." Zeit. f. wiss. Zool., XIV. 1864.
(176) H. Fol. Ein Beitrag z. Anat. u. Entwickl. einiger Rippenquallen. 1869.
(177) C. Gegenbaur. "Studien ü. Organis. u. System d. Ctenophoren." Archiv f. Naturgesch., XXII. 1856.
(178) A. Kowalevsky. "Entwicklungsgeschichte d. Rippenquallen." Mém. Acad. St Pétersbourg, VII. série, Tom. X. No. 4. 1866.
(179) J. Price. "Embryology of Ciliogrades." Proceed. of British Assoc., 1846.
(180) C. Semper. "Entwicklung d. Eucharis multicornis." Zeit. f. wiss. Zool., Vol. IX. 1858.
PLATYELMINTHES.
Turbellaria.
(181) Alex. Agassiz. "On the young stages of a few Annelids" (Planaria angulata). Annals Lyceum Nat. Hist. of New York, Vol. VIII. 1866.
(182) Dalyell. "Powers of the Creator."
(183) C. Girard. "Embryonic development of Planocera elliptica." Jour. Acad. of Nat. Sci., Philadelphia. New Series, Vol. II. 1854.
(184) Alex. Götte. "Zur Entwicklungsgeschichte d. Seeplanarien." Zoologischer Anzeiger, No. 4, 1878.
(185) P. Hallez. Contributions à l'histoire naturelle des Turbellariés. Thésis à la faculté des Sciences p. le grade d. Docteur ès-sciences naturelles. Lille, 1879.
(186) Knappert. "Bijdragen tot de Ontwikkelings-Geschiedenis der Zoetwater-Planarien." Provinciaal Utrechtsch Genootschap van Kunsten en Wetenschappen. Utrecht, 1865.
(187) W. Keferstein. "Beiträge z. Anat. u. Entwick. ein. Seeplanarien von St. Malo." Abh. d. könig. Gesell. d. Wiss. zu Göttingen. Bd. XIV. 1868.
(188) El. Metschnikoff. "Untersuchungen üb. d. Entwicklung d. Planarien." Notizen d. neurussischen Gesellschaft d. Naturforscher. Odessa, Bd. V. 1877. Vide Hoffman and Schwalbe's Bericht for 1878.
(189) H. N. Moseley. "On Stylochus pelagicus and a new species of pelagic Planarian, with notes on other pelagic species, on the larval forms of Thysanozoon, etc." Quart. Journ. of Micr. Science, Vol. XVII. 1877.
(190) J. Müller. "Ueber eine eigenthümliche Wurmlarva a. d. Classe d. Turbellarien, etc." Müller's Archiv f. Anat. u. Phys. 1850.
(191) J. Müller. "Ueber verschiedene Formen von Seethieren." Müller's Archiv f. Anat. und Phys. 1854.
Nemertea.
(192) J. Barrois. "L'Embryologie des Némertes." An. Sci. Nat., Vol. VI. 1877.
(193) O. Bütschli. Archiv f. Naturgeschichte, 1873.
(194) A. Krohn. "Ueb. Pilidium u. Actinotrocha." Müller's Archiv, 1858.
(195) E. Desor. "Embryology of Nemertes." Proceedings of the Boston Nat. History Society, Vol. VI. 1848.
(196) G. Dieck. "Entwicklungsgeschichte d. Nemertinen." Jenaische Zeitschrift, Vol. VIII. 1874.
(197) C. Gegenbaur. "Bemerkungen üb. Pilidium gyrans, etc." Zeitschrift für wiss. Zool., Bd. V. 1854.
(198) C. K. Hoffman. "Entwicklungsgeschichte von Tetrastemma tricolor." Niederländisches Archiv, Vol. III. 1876, 1877.
(199) C. K. Hoffman. "Zur Anatomie und Ontogenie von Malacobdella." Niederländisches Archiv, Vol. IV. 1877.
(200) W. C. McIntosh. British Annelids. The Nemerteans. Ray Society, 1873-4.
(201) Leuckart u. Pagenstecher. "Untersuchungen üb. niedere Seethiere." Müller's Archiv, 1858.
(202) E. Metschnikoff. "Studien üb. die Entwicklung d. Echinodermen u. Nemertinen." Mém. Acad. imp. Pétersbourg, VII. Ser., Tom. XIV. No. 8, 1869.
Trematoda.
(203) T. S. Cobbold. Entozoa. Groombridge and Son, 1864.
(204) T. S. Cobbold. Parasites; a Treatise on the Entozoa, etc. Churchill, 1879.
(205) Filippi. "Mém. p. servir à l'histoire génétique des Trématodes." Ann. Scien. Nat., 4th Series, Vol. II. 1854, and _Mem. Accad. Torino_, 1855-1859.
(206) R. Leuckart. Die menschlichen Parasiten, Vol. I. 1863, p. 485 et seq.
(207) H. A. Pagenstecher. Trematoden u. Trematodenlarven. Heidelberg, 1857.
(208) C. Th. von Siebold. Lehrbuch d. vergleich. Anat. wirbelloser Thiere. Berlin, 1848.
(209) J. J. S. Steenstrup. Generationswechsel. 1842.
(210) R. v. Willemoes-Suhm. "Zur Naturgeschichte d. Polystomum integerrimum, etc." Zeit. f. wiss. Zool., Vol. XXII. 1872.
(211) R. v. Willemoes-Suhm. "Helminthologische Notizen III." Zeit. f. wiss. Zool., Vol. XXIII. 1873. Vide this paper for a summary of known observations and literature.
(212) G. R. Wagener. Beiträge zur Entwicklungsgeschichte d. Eingeweidewürmer. Haarlem, 1855.
(213) G. R. Wagener. "Helminthologische Bemerkungen, etc." Zeit. f. wiss. Zool., Vol. IX. 1850.
(214) G. R. Wagener. "Ueb. Gyrodactylus elegans." Archiv f. Anat. u. Phys. 1860.
(215) E. Zeller. "Untersuchungen üb. d. Entwicklung d. Diplozoon paradoxum." Zeit. f. wiss. Zool., Vol. XXII. 1872.
(216) E. Zeller. "Untersuchungen ü. d. Entwick. u. Bau d. Polystomum integerrimum." Zeit. f. wiss. Zool., Vol. XXII. 1872.
(217) E. Zeller. "Weitere Beiträge z. Kenntniss d. Polystomen." Zeit. f. wiss. Zool., Vol. XXVII. 1876.
Cestoda.
(218) Ed. van Beneden. "Recherches sur la composition et la signification d. l'oeuf." Mém. cour. Acad. roy. Belgique. Vol. XXXIV. 1868.
(219) P. J. van Beneden. "Les vers Cestoïdes considérés sous le rapport physiologique embryogénique, etc." Bull. Acad. Scien. Bruxelles. Vol. XVII. 1850.
(220) T. S. Cobbold. Entozoa. Groombridge and Son, 1864.
(221) T. S. Cobbold. Parasites; a treatise on the Entozoa, etc. Churchill, 1879.
(222) Th. H. Huxley. "On the Anatomy and Development of Echinococcus veterinorum." Proc. Zool. Soc. Vol. XX. 1852.
(223) J. Knoch. "Die Naturgesch. d. breiten Bandwürmer." Mém. Acad. Imp. Pétersbourg, Vol. V. Ser. 7, 1863.
(224) F. Küchenmeister. "Ueber d. Umwandlung d. Finnen Cysticerci in Bandwürmer (Tænien)." Prag. Vierteljahrsschr. 1852.
(225) F. Küchenmeister. "Experimente üb. d. Entstehung d. Cestoden. 2e Stufe zunächst d. Coenurus cerebralis." Günsburg, Zeitsch. klin. Med. IV. 1853.
(226) R. Leuckart. Die menschlichen Parasiten, Vol. I. Leipzig, 1863. Vide also additions at the end of the 1st and 2nd volume.
(227) R. Leuckart. "Archigetes Sieboldii, eine geschlechtsreife Cestodenamme." Zeit. f. wiss. Zool., Vol. XXX. Supplement, 1878.
(228) El. Metschnikoff. "Observations sur le développement de quelques animaux (Bothriocephalus proboscideus)." Bull. Acad. Imp. St Pétersbourg, Vol. XIII. 1869.
(229) W. Salensky. "Ueb. d. Bau u. d. Entwicklungsgeschichte d. Amphilina." Zeit. f. wiss. Zool., Vol. XXIV. 1874.
(230) Von Siebold. Burdach's Physiologie.
(231) R. von Willemoes-Suhm. "Helminthologische Notizen." Zeit. f. wiss. Zool., Vol. XIX. XX. XXII. 1869, 70 and 73.
ROTIFERA.
(232) F. Cohn. "Ueb. d. Fortpflanzung von Räderthiere." Zeit. f. wiss. Zool., Vol. VII. 1856.
(233) F. Cohn. "Bemerkungen ü. Räderthiere." Zeit. f. wiss. Zool., Vol. IX. 1858, and Vol. XII. 1862.
(234) T. H. Huxley. "Lacinularia socialis." Trans. of the Microscopical Society, 1853.
(235) Fr. Leydig. "Ueb. d. Bau u. d. systematische Stellung d. Räderthiere." Zeit. f. wiss. Zool., Vol. VI. 1854.
(236) W. Salensky. "Beit. z. Entwick. von Brachionus urceolaris." Zeit. f. wiss. Zool., Vol. XXII. 1872.
(237) C. Semper. "Zoologische Aphorismen. Trochosphæra æquatorialis." Zeit. f. wiss. Zool., Vol. XXII. 1872.
MOLLUSCA.
General.
(238) T. H. Huxley. "On the Morphol. of the Cephal. Mollusca." Phil. Trans., 1853.
(239) E. R. Lankester. "On the developmental history of the Mollusca." Phil. Trans., 1875.
(240) H. G. Bronn and W. Keferstein. Die Klassen u. Ordnungen d. Thierreichs, Vol. III. 1862-1866.
Gasteropoda and Pteropoda.
(241) J. Alder and A. Hancock. "Devel. of Nudibr." Ann. and Magaz. Nat. Hist., Vol. XII. 1843.
(242) N. Bobretzky. "Studien über die embryonale Entwicklung d. Gasteropoden." Archiv f. mikr. Anat., Vol. XIII.
(243) W. K. Brooks. "Preliminary Observations on the Development of Marine Gasteropods." Chesapeake Zoological Laboratory, Session of 1878. Baltimore, 1879.
(244) O. Bütschli. "Entwicklungsgeschichtliche Beiträge (Paludina vivipara)." Zeit. f. wiss. Zool., Vol. XXIX. 1877.
(245) W. Carpenter. "On the devel. of the embr. of Purpura lapillus." Trans. Micros. Soc., 2d series, Vol. III. 1855.
(246) W. Carpenter. "On the devel. of the Purpura." Ann. and Mag. of Nat. Hist., 2d series, Vol. XX. 1857.
(247) E. Claparède. "Anatomie u. Entwickl. der Neritina fluviatilis." Müller's Archiv, 1857.
(248) H. Eisig. "Beitr. z. Anat. u. Entwickl. der Geschlechtsorg. von Lymnæus." Zeitschr. f. wiss. Zool., Vol. XIX. 1869.
(249) H. Fol. "Sur le développement des Ptéropodes." Archives de Zool. expérim. et générale, Vol. IV. 1875.
(250) H. Fol. "Sur le développement des Gastéropodes pulmonés." Compt. rend., 1875, pp. 523-526.
(251) H. Fol. "Sur le développement des Hétéropodes." Archives de Zool. expérim. et générale, Vol. V. 1876.
(252) C. Gegenbaur. "Beit. z. Entwicklungsgesch. der Landgasteropoden." Zeitschr. f. w. Zool., Vol. III. 1851.
(253) C. Gegenbaur. Untersuch. üb. Pteropoden u. Heteropoden. Leipzig, 1855.
(254) H. von Jhering. "Entwicklungsgeschichte von Helix." Jenaische Zeitschrift, Vol. IX. 1875.
(255) W. Keferstein and E. Ehlers. "Beob. üb. d. Entwick. v. Æolis peregr." Zool. Beitr., 1861.
(256) J. Koren and D. C. Danielssen. "Bemærk. til Mollusk. Udvikling." Nyt Mag. f. Naturvidensk., Vol. V. 1847. Isis, p. 202. 1848.
(257) J. Koren and D. C. Danielssen. Bidrag til Pectinibr. Udvikl. Bergen, 1851 (supplement, 1852). Ann. and Mag. Nat. Hist., 1857.
(258) A. Krohn. "Beobacht. aus d. Entwickl. der Pteropoden u. Heterop." Müller's Archiv, 1856 and 1857.
(259) A. Krohn. Beitr. zur Entwickl. der Pteropoden u. Heteropoden. Leipzig, 1860.
(260) H. de Lacaze-Duthiers. "Mém. sur l'anat. et l'embryog. des Vermets." 2e partie. Ann. sc. nat., 4e série, T. XIII. 1860.
(261) P. Langerhans. "Zur Entwickl. der Gasterop. Opisthobr." Zeitschr. f. w. Zool., Vol. XXIII. 1873.
(262) E. R. Lankester. "On the development of the Pond-Snail." Quart. J. of Micr. Scie., Vol. XIV. 1874.
(263) E. R. Lankester. "On the coincidence of the blastopore and anus in Paludina vivipara." Quart. J. of Micr. Scie., Vol. XVI. 1876.
(264) F. Leydig. "Ueber Paludina vivipara." Zeitschr. f. w. Zool., Vol. II. 1850.
(265) J. Müller. Ueber Synapta dig. u. üb. d. Erzeug. v. Schnecken in Holoth., 1852.
(266) J. Müller. "Bemerk. aus d. Entwickl. der Pteropoden." Monatsber. Berl. Akad., 1857.
(267) C. Rabl. "Die Ontogenie d. Süsswasser-Pulmonaten." Jenaische Zeitschrift, Vol. IX. 1875.
(268) C. Rabl. "Ueb. d. Entwick. d. Tellerschnecke (Planorbis)." Morph. Jahrbuch, Vol. V. 1879.
(269) W. Salensky. "Beitr. zur Entwickl. d. Prosobr." Zeitschr. f. w. Zool., Vol. XXII. 1872.
(270) O. Schmidt. "Ueb. Entwick. von Limax agrestis." Müller's Archiv, 1851.
(271) Max S. Schultze. "Ueber d. Entwick. des Tergipes lacinulatus." Arch. f. Naturg., Jahrg. XV. 1849.
(272) E. Selenka. "Entwick. von Tergipes claviger." Niederl. Arch. f. Zool., Vol. I. 1871.
(273) E. Selenka. "Die Anlage d. Keimbl. bei Purpura lapillus." Niederl. Arch. f. Zool., Vol. I. 1872.
(274) C. Semper. "Entwickl. der Ampullaria polita, etc." Natuurk. Verhandl. Utrechts Genootsch., 1862.
(275) An. Stecker. "Furchung u. Keimblatterbildung bei Calyptræa." Morphol. Jahrbuch, Vol. II. 1876.
(276) A. Stuart. "Ueb. d. Entwickl. einiger Opisthobr." Zeitschr. f. w. Zool., Vol. XV. 1865.
(277) N. A. Warneck. "Ueber d. Bild. u. Entwick. d. Embryos bei Gasterop." Bullet. Soc. naturel. de Moscou, T. XXIII. 1850.
Cephalopoda.
(278) P. J. van Beneden. "Recherches sur l'Embryogénie des Sépioles." Nouv. Mém. Acad. Roy. de Bruxelles, Vol. XIV. 1841.
(279) N. Bobretzky. Observation on the Development of the Cephalopoda (Russian). Nachrichten d. kaiserlichen Gesell. d. Freunde der Naturwiss. Anthropolog. Ethnogr. bei d. Universität Moskau.
(280) H. Grenacher. "Zur Entwicklungsgeschichte d. Cephalopoden." Zeit. f. wiss. Zool., Bd. XXIV. 1874.
(281) A. Kölliker. Entwicklungsgeschichte d. Cephalopoden. Zürich, 1844.
(282) E. R. Lankester. "Observations on the development of the Cephalopoda." Quart. J. of Micr. Science, Vol. XV. 1875.
(283) E. Metschnikoff. "Le développement des Sépioles." Archives d. Sc. phys. et nat., Vol. XXX. Genève, 1867.
Polyplacophora.
(284) A. Kowalevsky. "Ueb. d. Entwick. d. Chitonen." Zoologischer Anzeiger, No. 37. 1879.
(285) S. L. Lovén. "Om utvecklingen hos slägtet Chiton." Stockholm öfversigt, XII. 1855. [Vide also Ann. and Mag. of Nat. Hist., Vol. XVII. 1856, and Archiv f. Naturgeschichte, 1856.]
Scaphopoda.
(286) H. Lacaze-Duthiers. "Développement du Dentale." Ann. d. Sci. Nat., Series IV. Vol. VII. 1857.
Lamellibranchiata.
(287) M. Braun. "Postembryonale Entwicklung d. Süsswasser-Muscheln." Zoologischer Garten.
(288) C. G. Carus. "Neue Untersuch. üb. d. Entwickl. unserer Flussmuschel." Verh. Leop.-Car. Akad., Vol. XVI. 1832.
(289) W. Flemming. "Studien in d. Entwicklungsgeschichte der Najaden." Sitz. d. k. Akad. Wiss. Wien, Vol. LXXI. 1875.
(290) F. Leydig. "Ueber Cyclas Cornea." Müller's Archiv, 1855.
(291) S. L. Lovén. "Bidrag til Känned. om Utveckl. af Moll. Acephala Lamellibr." Vetensk. Akad. Handl., 1848. [Vide also Arch. f. Naturg., 1849.]
(292) C. Rabl. "Ueber d. Entwicklungsgeschichte d. Malermuschel." Jenaische Zeitschrift, Vol. X. 1876.
(293) W. Salensky. "Bemerkungen über Haeckels Gastræa-Theorie (Ostrea)." Arch. f. Naturg., 1874.
(294) O. Schmidt. "Ueb. d. Entwick. von Cyclas calyculata." Müller's Arch., 1854.
(295) O. Schmidt. "Zur Entwickl. der Najaden." Wien. Sitzungsber. math.-nat. Cl., Vol. XIX. 1856.
(296) P. Stepanoff. "Ueber die Geschlechtsorgane u. die Entwicklung von Cyclas." Archiv f. Naturgeschichte, 1865.
(297) H. Lacaze-Duthiers. "Développement d. branchies d. Mollusques Acéphales." An. Sc. Nat., Ser. IV. Vol. V. 1856.
POLYZOA.
General.
(298) J. Barrois. Recherches sur l'embryologie des Bryozoaires. Lille, 1877.
Entoprocta.
(299) B. Hatschek. "Embryonalentwicklung u. Knospung d. Pedicellina echinata." Zeitschrift für wiss. Zool., Bd. XXIX. 1877.
(300) M. Salensky. "Études sur les Bryozoaires entoproctes." Ann. Scien. Nat., Ser. VI. Tom. V. 1877.
(301) O. Schmidt. "Die Gattung Loxosoma." Archiv f. mik. Anat., Bd. XII. 1876.
(302) C. Vogt. "Sur le Loxosome des Phascolosomes." Archives de Zool. expér. et génér., Tom. V. 1876.
(303) C. Vogt. "Bemerkungen zu Dr Hatschek's Aufsatz üb. Embryonalentwicklung u. Knospung von Pedicellina echinata." Zeit. f. wiss. Zool., Bd. XXX. 1878.
Ectoprocta.
(304) G. J. Allman. Monograph of fresh-water Polyzoa. Ray Society.
(305) G. J. Allman. "On the structure of Cyphonautes." Quart. J. of Micr. Scie., Vol. XII. 1872.
(306) G. J. Allman. "On the structure and development of the Phylactolæmatous Polyzoa." Journal of the Linnean Society, Vol. XIV. No. 77. 1878.
(307) J. Barrois. "Le développement d. Bryozoaires Chilostomes." Comptes rendus, Sept. 23, 1878.
(308) E. Claparède. "Beiträge zur Anatomie u. Entwicklungsgeschichte d. Seebryozoen." Zeit. für wiss. Zool., Bd. XXI. 1871.
(309) E. Claparède. "Cyphonautes." Anat. u. Entwick. wirbell. Thiere. Leipzig, 1864.
(310) R. E. Grant. "Observations on the structure and nature of Flustræ." Edinburgh New Philosoph. Journal, 1827.
(311) B. Hatschek. "Embryonalentwicklung u. Knospung d. Pedicellina echinata." (Description of Cyphonautes). Zeit. f. wiss. Zool., Bd. XXIX. 1877.
(312) T. H. Huxley. "Note on the reproductive organs of the Cheilostome Polyzoa." Quart. Jour. of Micr. Science, Vol. IV. 1856.
(313) L. Joliet. "Contributions à l'histoire naturelle des Bryozoaires des côtes de France." Archives le Zoologie Expérimentale, Vol. VI. 1877.
(314) E. Metschnikoff. "Ueber d. Metamorphose einiger Seethiere." Göttingische Nachrichten, 1869. (315) E. Metschnikoff. Bull. de l'Acad. de St Pétersbourg, XV. 1871, p. 507.
(316) H. Nitsche. "Beiträge zur Kenntniss d. Bryozoen." Zeit. f. wiss. Zool., Bd. XX. 1870.
(317) W. Repiachoff. "Zur Naturgeschichte d. chilostomen Seebryozoen." Zeit. f. wiss. Zool., Bd. XXVI. 1876.
(318) W. Repiachoff. "Ueber die ersten Entwicklungsvorgänge bei Tendra zostericola." Zeit. f. wiss. Zool., Bd. XXX. 1878. Supplement.
(319) W. Repiachoff. "Zur Kenntniss der Bryozoen." Zoologischer Anzeiger, No. 10, Vol. I. 1878.
(320) W. Repiachoff. "Bemerkungen üb. Cyphonautes." Zoologischer Anzeiger, Vol. II. 1879.
(321) M. Salensky. "Untersuchung an Seebryozoen." Zeit. für wiss. Zool., Bd. XXIV. 1874.
(322) A. Schneider. "Die Entwicklung u. syst. Stellung d. Bryozoen u. Gephyreen." Archiv f. mikr. Anat., Vol. V. 1869.
(323) Smitt. "Om Hafsbryozoernas utveckling och fettkroppar." Aftryck ur öfvers. of Kong. Vet. Akad. Förh. Stockholm, 1865.
(324) T. Hincks. British Marine Polyzoa. Van Voorst, 1880.
[Conf. also works by Farre, Hincks, Van Beneden, Dalyell, Nordmann.]
BRACHIOPODA.
(325) W. K. Brooks. "Development of Lingula." Chesapeake Zoological Laboratory, Scientific Results of the Session of 1878. Baltimore, J. Murphy and Co.
(326) A. Kowalevsky. "Development of the Brachiopoda." Protocol of the First Session of the United Sections of Anatomy, Physiology, and Comparative Anatomy at the Meeting of Russian Naturalists in Kasan, 1873. (Russian.)
(327) H. Lacaze-Duthiers. "Histoire de la Thécidie." Ann. Scien. Nat. etc. Ser. 4, Vol. XV. 1861.
(328) Morse. "On the Early Stages of Terebratulina septentrionalis." Mem. Boston Soc. Nat. History, Vol. II. 1869, also Ann. & Mag. of Nat. Hist. Series 4, Vol. VIII. 1871.
(329) Morse. "On the Embryology of Terebratulina." Mem. Boston Soc. Nat. History, Vol. III. 1873.
(330) Morse. "On the Systematic Position of the Brachiopoda." Proceedings of the Boston Soc. of Nat. Hist., 1873.
(331) Fritz Müller. "Beschreibung einer Brachiopoden-Larve." Müller's Archiv, 1860.
CHÆTOPODA.
(332) Alex. Agassiz. "On the young stages of a few Annelids." Annals Lyceum Nat. Hist. of New York, Vol. VIII. 1866.
(333) Alex. Agassiz. "On the embryology of Autolytus cornutus and alternations of generations, etc." Boston Journal of Nat. History, Vol. VII. 1859-63.
(334) W. Busch. Beobachtungen ü. Anat. u. Entwick. einiger wirbelloser Seethiere, 1851.
(335) Ed. Claparède. Beobachtungen ü. Anat. u. Entwick. wirbelloser Thiere an d. Küste von Normandie. Leipzig, 1863.
(336) Ed. Claparède u. E. Metschnikoff. "Beiträge z. Kenntniss üb. Entwicklungsgeschichte d. Chætopoden." Zeit. f. wiss. Zool., Vol. XIX. 1869.
(337) E. Grube. Untersuchungen üb. Entwicklung d. Anneliden. Königsberg, 1844.
(338) B. Hatschek. "Beiträge z. Entwick. u. Morphol. d. Anneliden." Sitz. d. k. Akad. Wiss. Wien, Vol. LXXIV. 1876.
(339) B. Hatschek. "Studien über Entwicklungsgeschichte der Anneliden." Arbeiten aus d. zoologischen Institute d. Universität Wien. Von C. Claus. Heft III. 1878.
(340) Th. H. Huxley. "On hermaphrodite and fissiparous species of tubicolar Annelidæ (Protula)." Edinburgh New Phil. Journal, Vol. I. 1855.
(341) N. Kleinenberg. "The development of the earthworm Lumbricus trapezoides." Quart. J. of Micr. Science, Vol. XIX. 1879. Sullo sviluppo del Lumbricus trapezoides. Napoli, 1878.
(342) A. Kowalevsky. "Embryologische Studien an Würmern u. Arthropoden." Mém. Acad. Pétersbourg, Series VII. Vol. XVI. 1871.
(343) A. Krohn. "Ueber die Erscheinungen bei d. Fortpflanzung von Syllis prolifera u. Autolytus prolifer." Archiv f. Naturgesch. 1852.
(344) R. Leuckart. "Ueb. d. Jugendzustände ein. Anneliden, etc." Archiv f. Naturgesch. 1855.
(345) S. Lovén. "Beobachtungen ü. die Metamorphose von Anneliden." Wiegmann's Archiv, 1842.
(346) E. Metschnikoff. "Ueber die Metamorphose einiger Seethiere (Mitraria)." Zeit. f. wiss. Zool., Vol. XXI. 1871.
(347) M. Milne-Edwards. "Recherches zoologiques, etc." Ann. Scie. Natur. III. Série, Vol. III. 1845.
(348) J. Müller. "Ueb. d. Jugendzustände einiger Seethiere." Monats. d. k. Akad. Wiss. Berlin, 1851.
(349) Max Müller. "Ueber d. weit. Entwick. von Mesotrocha sexoculata." Müller's Archiv, 1855.
(350) Quatrefages. "Mémoire s. l'embryogénie des Annelides." Ann. Scie. Natur. III. Série, Vol. X. 1848.
(351) M. Sars. "Zur Entwicklung d. Anneliden." Archiv f. Naturgeschichte, Vol. XI. 1845.
(352) A. Schneider. "Ueber Bau u. Entwicklung von Polygordius." Müller's Archiv, 1868.
(353) A. Schneider. "Entwicklung u. system. Stell. d. Bryozoen u. Gephyreen (Mitraria)." Archiv f. mikr. Anat. Vol. V. 1869.
(354) M. Schultze. Ueb. die Entwicklung von Arenicola piscatorum u. anderer Kiemenwürmer. Halle, 1856.
(355) C. Semper. "Die Verwandschaftbeziehungen d. gegliederten Thiere." Arbeiten a. d. zool.-zoot. Instit. Würzburg, Vol. III. 1876-7.
(356) C. Semper. "Beiträge z. Biologie d. Oligochæten." Arbeiten a. d. zool.-zoot Instit. Würzburg, Vol. IV. 1877-8.
(357) M. Stossich. "Beiträge zur Entwicklung d. Chætopoden." Sitz. d. k. k. Akad. Wiss. Wien, B. LXXVII. 1878.
(358) R. v. Willemoes-Suhm. "Biologische Beobachtungen ü. niedrige Meeresthiere." Zeit. f. wiss. Zool. Bd. XXI. 1871.
DISCOPHORA.
(359) O. Bütschli. "Entwicklungsgeschichtliche Beiträge (Nephelis)." Zeit. f. wiss. Zool. Vol. XXIX. 1877.
(360) E. Grube. Untersuchungen üb. d. Entwicklung d. Anneliden. Königsberg, 1844.
(361) C. K. Hoffmann. "Zur Entwicklungsgeschichte d. Clepsineen." Niederländ. Archiv f. Zool. Vol. IV. 1877.
(362) R. Leuckart. Die menschlichen Parasiten (Hirudo), Vol. I. p. 686, et seq.
(363) H. Rathke. Beit. z. Entwicklungsgesch. d. Hirudineen. Leipzig, 1862.
(364) Ch. Robin. Mém. sur le Développement embryogénique des Hirudinées. Paris, 1875.
(365) C. O. Whitman. "Embryology of Clepsine." Quart. J. of Micro. Science, Vol. XVIII. 1878.
[Vide also C. Semper (No. 355) and Kowalevsky (No. 342) for isolated observations.]
GEPHYREA.
Gephyrea nuda.
(366) A. Kowalevsky. Sitz. d. zool. Abth. d. III. Versam. russ. Naturj. (Thalassema). Zeit. f. wiss. Zool. Vol. XXII. 1872, p. 284.
(367) A. Krohn. "Ueb. d. Larve d. Sipunculus nudus nebst Bemerkungen," etc. Müller's Archiv, 1857.
(368) M. Salensky. "Ueber die Metamorphose d. Echiurus." Morphologisches Jahrbuch, Bd. II.
(369) E. Selenka. "Eifurchung u. Larvenbildung von Phascolosoma elongatum." Zeit. f. wiss. Zool. 1875, Bd. XXV. p. 1.
(370) J. W. Spengel. "Beiträge z. Kenntniss d. Gephyreen (Bonellia)." Mittheil. a. d. zool. Station z. Neapel, Vol. I. 1879.
Gephyrea tubicola (Actinotrocha).
(371) A. Krohn. "Ueb. Pilidium u. Actinotrocha." Müller's Archiv, 1858.
(372) A. Kowalevsky. "On anatomy and development of Phoronis," Petersburg, 1867. 2 Pl. Russian. Vide Leuckart's Bericht, 1866-7.
(373) E. Metschnikoff. "Ueber d. Metamorphose einiger Seethiere (Actinotrocha)." Zeit. f. wiss. Zool. Bd. XXI. 1871.
(374) J. Müller. "Bericht üb. ein. Thierformen d. Nordsee." Müller's Archiv, 1846.
(375) An. Schneider. "Ueb. d. Metamorphose d. Actinotrocha branchiata." Müller's Arch., 1862.
CHÆTOGNATHA.
(376) O. Bütschli. "Zur Entwicklungsgeschichte der Sagitta." Zeitschrift f. wiss. Zool., Vol. XXIII. 1873.
(377) C. Gegenbaur. "Ueber die Entwicklung der Sagitta." Abhand. d. naturforschenden Gesellschaft in Halle, 1857.
(378) A. Kowalevsky. "Embryologische Studien an Würmern u. Arthropoden." Mém. Acad. Pétersbourg, VII. sér., Tom. XVI., No. 12. 1871.
MYZOSTOMEA.
(379) L. Graff. Das Genus Myzostoma. Leipzig, 1877.
(380) E. Metschnikoff. "Zur Entwicklungsgeschichte d. Myzostomum." Zeit. f wiss. Zool., Vol. XVI. 1866.
(381) C. Semper. "Z. Anat. u. Entwick. d. Gat. Myzostomum." Zeit. f. wiss. Zool., Vol. IX. 1858.
GASTROTRICHA.
(382) H. Ludwig. "Ueber die Ordnung Gastrotricha Metschn." Zeit. f. wiss. Zool., Vol. XXVI. 1876.
NEMATELMINTHES.
(383) O. Bütschli. "Entwicklungsgeschichte d. Cucullanus elegans." Zeit. f. wiss. Zool., B. XXVI. 1876.
(384) T. S. Cobbold. Entozoa. Groombridge and Son, 1864.
(385) T. S. Cobbold. Parasites: a Treatise on the Entozoa of Man and Animals. Churchill, 1879.
(386) O. Galeb. "Organisation et développement des Oxyuridés," etc. Archives de Zool. expér. et génér., Vol. VII. 1878.
(387) R. Leuckart. Untersuchungen üb. Trichina spiralis. 2nd ed. Leipzig, 1866.
(388) R. Leuckart. Die menschlichen Parasiten, Bd. II. 1876.
(389) H. A. Pagenstecher. Die Trichinen nach Versuchen dargestellt. Leipzig, 1865.
(390) A. Schneider. Monographie d. Nematoden. Berlin, 1866.
(391) A. Villot. "Monographie des Dragoneaux" (Gordioidea). Archives de Zool. expér. et génér., Vol. III. 1874.
ACANTHOCEPHALA.
(392) R. Greeff. "Untersuchungen ü. d. Bau u. Entwicklung des Echin. miliarius." Archiv f. Naturgesch. 1864.
(393) R. Leuckart. Die menschlichen Parasiten. Vol. II. p. 801 et seq. 1876. (394) An. Schneider. "Ueb. d. Bau d. Acanthocephalen." Archiv f. Anat. u. Phys. 1868.
(395) G. R. Wagener. Beiträge z. Entwicklungsgeschichte d. Eingeweidewürmer. Haarlem, 1865.
TRACHEATA.
PROTOTRACHEATA.
(396) H. N. Moseley. "On the Structure and Development of Peripatus capensis." Phil. Trans. Vol. 164, 1874.
MYRIAPODA.
(397) G. Newport. "On the Organs of Reproduction and Development of the Myriapoda." Philosophical Transactions, 1841.
(398) E. Metschnikoff. "Embryologie der doppeltfüssigen Myriapoden (Chilognatha)." Zeit. f. wiss. Zool., Vol. XXIV. 1874.
(399) E. Metschnikoff. "Embryologisches über Geophilus." Zeit. f. wiss. Zool., Vol. XXV. 1875.
(400) Anton Stecker. "Die Anlage d. Keimblatter bei den Diplopoden." Archiv f. mik. Anatomie, Bd. XIV. 1877.
INSECTA.
(401) M. Balbiani. "Observations s. la reproduction d. Phylloxera du Chêne." An. Sc. Nat. Ser. V. Vol. XIX. 1874.
(402) E. Bessels. "Studien ü. d. Entwicklung d. Sexualdrüsen bei den Lepidoptera." Zeit. f. wiss. Zool. Bd. XVII. 1867.
(403) Alex. Brandt. "Beiträge zur Entwicklungsgeschichte d. Libellulida u. Hemiptera, mit besonderer Berücksichtigung d. Embryonalhüllen derselben." Mém. Ac. Pétersbourg, Ser. VII. Vol. XIII. 1869.
(404) Alex. Brandt. Ueber das Ei u. seine Bildungsstätte. Leipzig, 1878.
(405) O. Bütschli. "Zur Entwicklungsgeschichte d. Biene." Zeit. f. wiss. Zool. Bd. XX. 1870.
(406) H. Dewitz. "Bau u. Entwicklung d. Stachels, etc." Zeit. f. wiss. Zool. Vols. XXV. and XXVIII. 1875 and 1877.
(407) H. Dewitz. "Beiträge zur Kenntniss d. Postembryonalentwicklung d. Gliedmassen bei den Insecten." Zeit. f. wiss. Zool. XXX. Supplement. 1878.
(408) A. Dohrn. "Notizen zur Kenntniss d. Insectenentwicklung." Zeitschrift f. wiss. Zool. Bd. XXVI. 1876.
(409) M. Fabre. "L'hypermétamorphose et les moeurs des Méloïdes." An. Sci. Nat. Series IV. Vol. VII. 1857.
(410) Ganin. "Beiträge zur Erkenntniss d. Entwicklungsgeschichte d. Insecten." Zeit. f. wiss. Zool. Bd. XIX. 1869.
(411) V. Graber. Die Insecten. München, 1877.
(412) V. Graber. "Vorläuf. Ergeb. üb. vergl. Embryologie d. Insecten." Archiv f. mikr. Anat. Vol. XV. 1878.
(413) O. v. Grimm. "Ungeschlechtliche Fortpflanzung einer Chironomus-Art u. deren Entwicklung aus dem unbefruchteten Ei." Mém. Acad. Pétersbourg. 1870.
(414) B. Hatschek. "Beiträge zur Entwicklung d. Lepidopteren." Jenaische Zeitschrift, Bd. XI.
(415) A. Kölliker. "Observationes de primâ insectorum genese, etc." Ann. Sc. Nat. Vol. XX. 1843.
(416) A. Kowalevsky. "Embryologische Studien an Würmern u. Arthropoden." Mém. Ac. imp. Pétersbourg, Ser. VII. Vol. XVI. 1871.
(417) C. Kraepelin. "Untersuchungen üb. d. Bau, Mechanismus u. d. Entwick. des Stachels d. bienartigen Thiere." Zeit. f. wiss. Zool. Vol. XXIII. 1873.
(418) C. Kupffer. "Faltenblatt an d. Embryonen d. Gattung Chironomus." Arch. f. mikr. Anat. Vol. II. 1866.
(419) R. Leuckart. Zur Kenntniss d. Generationswechsels u. d. Parthenogenese b. d. Insecten. Frankfurt, 1858.
(420) Lubbock. Origin and Metamorphosis of Insects. 1874.
(421) Lubbock. Monograph on Collembola and Thysanura. Ray Society, 1873.
(422) Melnikow. "Beiträge z. Embryonalentwicklung d. Insecten." Archiv f. Naturgeschichte, Bd. XXXV. 1869.
(423) E. Metschnikoff. "Embryologische Studien an Insecten." Zeit. f. wiss. Zool. Bd. XVI. 1866.
(424) P. Meyer. "Ontogenie und Phylogenie d. Insecten." Jenaische Zeitschrift, Vol. X. 1876.
(425) Fritz Müller. "Beiträge z. Kenntniss d. Termiten." Jenaische Zeitschrift, Vol. IX. 1875.
(426) A. S. Packard. "Embryological Studies on Diplex, Perithemis, and the Thysanurous genus Isotoma." Mem. Peabody Acad. Science, 1. 2. 1871.
(427) Suckow. "Geschlechtsorgane d. Insecten." Heusinger's Zeitschrift f. organ. Physik, Bd. II. 1828.
(428) Tichomiroff. "Ueber die Entwicklungsgeschichte des Seidenwurms." Zoologischer Anzeiger, II. Jahr. No. 20 (Preliminary Notice).
(429) Aug. Weismann. "Zur Embryologie d. Insecten." Archiv f. Anat. und Phys. 1864.
(430) Aug. Weismann. "Entwicklung d. Dipteren." Zeit. f. wiss. Zool. Vols. XIII. and XIV. Leipzig, 1863-4.
(431) Aug. Weismann. "Die Metamorphose d. Corethra plumicornis." Zeit. f. wiss. Zool. Vol. XVI. 1866.
(432) N. Wagner. "Beitrag z. Lehre d. Fortpflanzung d. Insectenlarven." Zeit. f. wiss. Zool. Vol. XIII. 1860.
(433) Zaddach. Untersuchungen üb. d. Bau u. d. Entwicklung d. Gliederthiere. Berlin, 1854.
ARACHNIDA.
Scorpionidæ.
(434) El. Metschnikoff. "Embryologie des Scorpions." Zeit. f. wiss. Zool. Bd. XXI. 1870.
(435) H. Rathke. Reisebemerkungen aus Taurien (Scorpio). Leipzig, 1837.
Pseudoscorpionidæ.
(436) El. Metschnikoff. "Entwicklungsgeschichte d. Chelifer." Zeit. f. wiss. Zool. Bd. XXI. 1870.
(437) A. Stecker. "Entwicklung der Chthonius-Eier im Mutterleibe und die Bildung des Blastoderms." Sitzung. königl. böhmisch. Gesellschaft Wissensch., 1876, 3. Heft, and Annal. and Mag. Nat. History, 1876, XVIII. 197.
Phalangidæ.
(438) M. Balbiani. "Mémoire sur le développement des Phalangides." Ann. Scien. Nat. Series V. Vol. XVI. 1872.
Araneina.
(439) M. Balbiani. "Mémoire sur le développement des Aranéides." Ann. Scien. Nat. Series V. Vol. XVII. 1873.
(440) F. M. Balfour. "Notes on the development of the Araneina." Quart. Journ. of Micr. Science, Vol. XX. 1880.
(441) J. Barrois. "Recherches s. l. développement des Araignées." Journal de l'Anat. et de la Physiol. 1878.
(442) E. Claparède. Recherches s. l'évolution des Araignées. Utrecht, 1862.
(443) Herold. De generatione Araneorum in Ovo. Marburg, 1824.
(444) H. Ludwig. "Ueber die Bildung des Blastoderms bei den Spinnen." Zeit. f. wiss. Zool. Vol. XXVI. 1876.
Acarina.
(445) P. van Beneden. "Développement de l'Atax ypsilophora." Acad. Bruxelles, t. XXIV.
(446) Ed. Claparède. "Studien über Acarinen." Zeit. f. wiss. Zool., Bd. XVIII. 1868.
CRUSTACEA.
General Works.
(447) C. Spence Bate. "Report on the present state of our knowledge of the Crustacea." Report of the British Association for 1878.
(448) C. Claus. Untersuchungen zur Erforschung der genealogischen Grundlage des Crustaceen-Systems. Wien, 1876.
(449) A. Dohrn. "Geschichte des Krebsstammes." Jenaische Zeitschrift, Vol. VI. 1871.
(450) A. Gerstaecker. Bronn's Thierreich, Bd. V. Arthropoda, 1866.
(451) Th. H. Huxley. The Anatomy of Invertebrated Animals. London, 1877.
(452) Fritz Müller. Für Darwin, 1864. Translation, Facts for Darwin. London, 1869.
Branchiopoda.
(453) Brauer. "Vorläufige Mittheilung über die Entwicklung u. Lebensweise des Lepidurus (Apus) productus." _Sitz. der Ak. d. Wiss. Wien_, Vol. LXIX., 1874.
(454) C. Claus. "Zur Kenntniss d. Baues u. d. Entwicklung von Branchipus stagnalis u. Apus cancriformis." Abh. d. könig. Gesell. der Wiss. Göttingen, Vol. XVIII. 1873.
(455) C. Grobben. "Zur Entwicklungsgeschichte d. Moina rectirostris." Arbeit. a. d. zoologisch. Institute Wien, Vol. II., 1879.
(456) E. Grube. "Bemerkungen über die Phyllopoden nebst einer Uebersicht etc." Archiv f. Naturgeschichte, Vol. XIX., 1853.
(457) N. Joly. "Histoire d'un petit Crustacé (Artemia salina, Leach) etc." Annales d. Sciences Natur., 2nd ser., Vol. XIII., 1840.
(458) N. Joly. "Recherches zoologiques anatomiques et physiologiques sur l'Isaura cycladoides (=Estheria) nouveau genre, etc." Annales d. Sciences Nat., and ser., Vol. XVII., 1842.
(459) Lereboullet. "Observations sur la génération et le développement de la Limnadia de Hermann." Annales d. Sciences Natur., 5th ser., Vol. V., 1866.
(460) F. Leydig. "Ueber Artemia salina u. Branchipus stagnalis." Zeit. f. wiss. Zool., Vol. III., 1851.
(461) G. O. Sars. "Om en dimorph Udvikling samt Generationsvexel hos Leptodora." Vidensk. Selskab. Forhand, 1873.
(462) G. Zaddach. De apodis cancreformis Schaeff. anatome et historia evolutionis. Dissertatio inauguralis zootomica. Bonnæ, 1841.
Nebaliadæ.
(463) C. Claus. "Ueber den Bau u. die systematische Stellung von Nebalia." Zeit. f. wiss. Zool., Bd. XXII. 1872.
(464) E. Metschnikoff. Development of Nebalia (Russian), 1868.
Schizopoda.
(465) E. van Beneden. "Recherches sur l'Embryogénie des Crustacés. II. Développement des Mysis." Bullet. de l'Académie roy. de Belgique, second series, Tom. XXVIII. 1869.
(466) C. Claus. "Ueber einige Schizopoden u. niedere Malakostraken." Zeit. f. wiss. Zoologie, Bd. XIII., 1863. (467) A. Dohrn. "Untersuchungen üb. Bau u. Entwicklung d. Arthropoden." Zeit. f. wiss. Zool., Bd. XXI., 1871, p. 375. Peneus zoæa (larva of Euphausia).
(468) E. Metschnikoff. "Ueber ein Larvenstadium von Euphausia." Zeit. für wiss. Zool., Bd. XIX., 1869.
(469) E. Metschnikoff. "Ueber den Naupliuszustand von Euphausia." Zeit. für wiss. Zool., Bd. XXI., 1871.
Decapoda.
(470) Spence Bate. "On the development of Decapod Crustacea." Phil. Trans., 1858.
(471) Spence Bate. "On the development of Pagurus." Ann. and Mag. Nat. History, Series 4, Vol. II., 1868.
(472) N. Bobretzky. Development of Astacus and Palæmon. Kiew, 1873. (Russian.)
(473) C. Claus. "Zur Kenntniss d. Malakostrakenlarven." Würzb. naturw. Zeitschrift, 1861.
(474) R. Q. Couch. "On the Metamorphosis of the Decapod Crustaceans." Report Cornwall Polyt. Society, 1848.
(475) Du Cane. "On the Metamorphosis of Crustacea." Ann. and Mag. of Nat. History, 1839.
(476) Walter Faxon. "On the development of Palæmonetes vulgaris." Bull. of the Mus. of Comp. Anat. Harvard, Cambridge, Mass., Vol. V., 1879.
(477) A. Dohrn. "Untersuchungen üb. Bau u. Entwicklung d. Arthropoden." "Zur Entwicklungsgeschichte der Panzerkrebse. Scyllarus Palinurus." Zeit. f. wiss. Zool., Bd. XIX., 1870.
(478) A. Dohrn. "Untersuchungen üb. Bau u. Entwicklung d. Arthropoden. Erster Beitrag z. Kenntniss d. Malacostraken u. ihrer Larven Amphion Reynaudi, Lophogaster, Portunus, Porcellanus, Elaphocaris." Zeit. f. wiss. Zool., Bd. XX., 1870.
(479) A. Dohrn. "Untersuchungen üb. Bau u. Entwicklung d. Arthropoden. Zweiter Beitrag, etc." Zeit. f. wiss. Zool., Bd. XXI., 1871.
(480) N. Joly. "Sur la Caridina Desmarestii." Ann. Scien. Nat., Tom. XIX., 1843.
(481) Lereboullet. "Recherches d. l'embryologie comparée sur le développement du Brochet, de la Perche et de l'Écrevisse." Mem. Savans Etrang. Paris, Vol. XVII., 1862.
(482) P. Mayer. "Zur Entwicklungsgeschichte d. Dekapoden." Jenaische Zeitschrift, Vol. XI., 1877.
(483) Fritz Müller. "Die Verwandlung der Porcellana." Archiv f. Naturgeschichte, 1862.
(484) Fritz Müller. "Die Verwandlungen d. Garneelen." Archiv f. Naturgesch., Tom. XXIX.
(485) Fritz Müller. "Ueber die Naupliusbrut d. Garneelen." Zeit. f. wiss. Zool., Bd. XXX., 1878.
(486) T. J. Parker. "An account of Reichenbach's researches on the early development of the Fresh-water Crayfish." Quart. F. of M. Science, Vol. XVIII., 1878.
(487) H. Rathke. Ueber die Bildung u. Entwicklung d. Flusskrebses. Leipzig, 1829.
(488) H. Reichenbach. "Die Embryoanlage u. erste Entwicklung d. Flusskrebses." Zeit. f. wiss. Zool., Vol. XXIX., 1877.
(489) F. Richters. "Ein Beitrag zur Entwicklungsgeschichte d. Loricaten." Zeit. f. wiss. Zool., Bd. XXIII., 1873.
(490) G. O. Sars. "Om Hummers postembryonale Udvikling." Vidensk Selsk. Forh. Christiania, 1874.
(491) Sidney J. Smith. "The early stages of the American Lobster." Trans. of the Connecticut Acad. of Arts and Sciences, Vol. II., Part 2, 1873.
(492) R. v. Willemoes Suhm. "Preliminary note on the development of some pelagic Decapoda." Proc. of Royal Society, 1876.
Stomatopoda.
(493) W. K. Brooks. "On the larval stages of Squilla empusa." Chesapeake Zoological Laboratory, Scientific results of the Session of 1878. Baltimore, 1879.
(494) C. Claus. "Die Metamorphose der Squilliden." Abhand. der königl. Gesell. der Wiss. zu Göttingen, 1871.
(495) Fr. Müller. "Bruchstück a. der Entwicklungsgeschichte d. Maulfüsser I. und II." Archiv f. Naturgeschichte, Vol. XXVIII., 1862, and Vol. XXIX., 1863.
Cumacea.
(496) A. Dohrn. "Ueber den Bau u. Entwicklung d. Cumaceen." Jenaische Zeitschrift, Vol. V., 1870.
Isopoda.
(497) Ed. van Beneden. "Recherches sur l'Embryogénie des Crustacés. I. Asellus aquaticus." Bull. de l'Acad. roy. Belgique, 2me série, Tom. XXVIII., No. 7, 1869.
(498) N. Bobretzky. "Zur Embryologie des Oniscus murarius." Zeit. für wiss. Zool., Bd. XXIV., 1874.
(499) J. F. Bullar. "On the development of the parasitic Isopoda." Phil. Trans., Part II., 1878.
(500) A. Dohrn. "Die embryonale Entwicklung des Asellus aquaticus." Zeit. f. wiss. Zool., Vol. XVII., 1867.
(501) H. Rathke. Untersuchungen über die Bildung and Entwicklung der Wasser-Assel. Leipzig, 1832.
(502) H. Rathke. Zur Morphologie. Reisebemerkungen aus Taurien. Riga u. Leipzig, 1837. (Bopyrus, Idothea, Ligia, Ianira.)
Amphipoda.
(503) Ed. van Beneden and E. Bessels. "Mémoire sur la formation du blastoderme chez les Amphipodes, les Lernéens et les Copépodes." Classe des Sciences de l'Acad. roy. de Belgique, Vol. XXXIV., 1868.
(504) De la Valette St George. "Studien über die Entwicklung der Amphipoden." Abhand. d. naturfor. Gesell. zu Halle, Bd. V., 1860.
Copepoda.
(505) E. van Beneden and E. Bessels. "Mémoire sur la formation du blastoderme chez les Amphipodes, les Lernéens et Copépodes." Classe des Sciences de l'Acad. roy. de Belgique, Vol. XXXIV., 1868.
(506) E. van Beneden. "Recherches sur l'Embryogénie des Crustacés IV. Anchorella, Lerneopoda, Branchiella, Hessia." Bull. de l'Acad. roy. de Belgique, 2me série, T. XXIX., 1870.
(507) C. Claus. Zur Anatomie u. Entwicklungsgeschichte d. Copepoden.
(508) C. Claus. "Untersuchungen über die Organisation u. Verwandschaft d. Copepoden." Würzburger naturwiss. Zeitschrift, Bd. III., 1862.
(509) C. Claus. "Ueber den Bau u. d. Entwicklung von Achtheres percarum." Zeit. f. wiss. Zool., Bd. XI., 1862.
(510) C. Claus. Die freilebenden Copepoden mit besonderer Berücksichtigung der Fauna Deutschlands, der Nordsee u. des Mittelmeeres. Leipzig, 1863.
(511) C. Claus. "Ueber d. Entwicklung, Organisation u. systematische Stellung d. Argulidæ." Zeit. f. wiss. Zool., Bd. XXV., 1875.
(512) P. P. C. Hoek. "Zur Entwicklungsgeschichte d. Entomostracen." Niederlandisches Archiv, Vol. IV., 1877.
(513) Nordmann. Mikrographische Beiträge zur Naturgeschichte der wirbellosen Thiere. Zweites Heft. 1832.
(514) Salensky. "Sphæronella Leuckartii." Archiv f. Naturgeschichte, 1868.
(515) F. Vejdovsky. "Untersuchtingen üb. d. Anat. u. Metamorph. v. Trachebastes polycolpus." ZEIT. F. WISS. ZOOL., Vol. XXIX., 1877.
Cirripedia.
(516) C. Spence Bate. "On the development of the Cirripedia." Annals and Mag. of Natur. History. Second Series, VIII., 1851.
(517) E. van Beneden. "Développement des Sacculines." Bull. de l'Acad. roy. de Belg., 1870.
(518) C. Claus. Die Cypris-ähnliche Larve der Cirripedien. Marburg, 1869.
(519) Ch. Darwin. A monograph of the sub-class Cirripedia, 2 Vols., Ray Society, 1851-4.
(520) A. Dohrn. "Untersuchungen über Bau u. Entwicklung d. Arthropoden IX. Eine neue Naupliusform (Archizoëa gigas)." Zeit. f. wiss. Zool., Bd. XX., 1870.
(521) P. P. C. Hoek. "Zur Entwicklungsgeschichte der Entomostraken I. Embryologie von Balanus." Niederländisches Archiv für Zoologie, Vol. III., 1876-7.
(522) R. Kossmann. "Suctoria u. Lepadidæ." Arbeiten a. d. zool.-zoot. Institute d. Univer. Würz., Vol. I., 1873.
(523) Aug. Krohn. "Beobachtungen über die Entwicklung der Cirripedien." Wiegmann's Archiv für Naturgesch., XXVI., 1860.
(524) E. Metschnikoff. Sitzungsberichte d. Versammlung deutscher Naturforscher zu Hannover, 1865. (Balanus balanoides.)
(525) Fritz Müller. "Die Rhizocephalen." Archiv f. Naturgeschichte, 1862-3.
(526) F. C. Noll. "Kochlorine hamata, ein bohrendes Cirriped." Zeit. f. wiss. Zool., Bd. XXV., 1875.
(527) A. Pagenstecher. "Beiträge zur Anatomie und Entwicklungsgeschichte von Lepas pectinata." Zeit. f. wiss. Zool., Vol. XIII., 1863.
(528) J. V. Thompson. Zoological Researches and Illustrations, Vol. I., Part 1. Memoir IV. On the Cirripedes or Barnacles. 8vo. Cork, 1830.
(529) J. V. Thompson. "Discovery of the Metamorphosis in the second type of the Cirripedes, viz. the Lepades completing the natural history of these singular animals, and confirming their affinity with the Crustacea." Phil. Trans. 1835. Part II.
(530) R. von Willemoes Suhm. "On the development of Lepas fascicularis." Phil. Trans., Vol. 166, 1876.
Ostracoda.
(531) C. Claus. "Zur näheren Kenntniss der Jugendformen von Cypris ovum." Zeit. f. wiss. Zool., Bd. XV., 1865.
(532) C. Claus. "Beiträge zur Kenntniss d. Ostracoden. Entwicklungsgeschichte von Cypris ovum." Schriften d. Gesell. zur Beförderung d. gesamm. Naturwiss. zu Marburg, Vol. IX., 1868.
POECILOPODA.
(533) A. Dohrn. "Untersuch. üb. Bau u. Entwick. d. Arthropoden (Limulus polyphemus)." Jenaische Zeitschrift, Vol. VI., 1871.
(534) A. S. Packard. "The development of Limulus polyphemus." Mem. Boston Soc. Nat. History, Vol. II., 1872.
PYCNOGONIDA.
(535) G. Cavanna. "Studie e ricerche sui Pienogonidi." Pubblicazioni del R. Instituto di Studi superiori in Firenze, 1877.
(536) An. Dohrn. "Ueber Entwicklung u. Bau d. Pycnogoniden." Jenaische Zeitschrift, Vol. V. 1870, and "Neue Untersuchungen üb. Pycnogoniden." Mittheil. a. d. zoologischen Station zu Neapel, Bd. I. 1878.
(537) G. Hodge. "Observations on a species of Pycnogon, etc." Annal. and Mag. of Nat. Hist. Vol. IX. 1862.
(538) C. Semper. "Ueber Pycnogoniden u. ihre in Hydroiden schmarotzenden Larvenformen." Arbeiten a. d. zool.-zoot. Instit. Würzburg, Vol. I. 1874.
PENTASTOMIDA.
(539) P. J. van Beneden. "Recherches s. l'organisation et le développement d. Linguatules." Ann. d. Scien. Nat., 3 Ser., Vol. XI.
(540) R. Leuckart. "Bau u. Entwicklungsgeschichte d. Pentastomen." Leipzig and Heidelberg. 1860.
TARDIGRADA.
(541) J. Kaufmann. "Ueber die Entwicklung u. systematische Stellung d. Tardigraden." Zeit. f. wiss. Zool., Bd. III. 1851.
ECHINODERMATA.
(542) Alex. Agassiz. Revision of the Echini. Cambridge, U.S. 1872-74.
(543) Alex. Agassiz. "North American Starfishes." Memoirs of the Museum of Comparative Anatomy and Zoology at Harvard College, Vol. V., No. 1. 1877 (originally published in 1864).
(544) J. Barrois. "Embryogénie de l'Asteriscus verruculatus." Journal de l'Anat. et Phys. 1879.
(545) A. Baur. Beiträge zur Naturgeschichte d. Synapta digitata. Dresden, 1864.
(546) H. G. Bronn. Klassen u. Ordnungen etc. Strahlenthiere, Vol. II. 1860.
(547) W. B. Carpenter. "Researches on the structure, physiology and development of Antedon." Phil. Trans. CLVI. 1866, and Proceedings of the Roy. Soc., No. 166. 1876.
(548) P. H. Carpenter. "On the oral and apical systems of the Echinoderms." Quart. J. of Micr. Science, Vol. XVIII. and XIX. 1878-9.
(549) A. Götte. "Vergleichende Entwicklungsgeschichte d. Comatula mediterranea." Arch. für micr. Anat., Vol. XII. 1876.
(550) R. Greeff. "Ueber die Entwicklung des Asteracanthion rubens vom Ei bis zur Bipinnaria u. Brachiolaria." Schriften d. Gesellschaft zur Beförderung d. gesammten Naturwissenschaften zu Marburg, Bd. XII. 1876.
(551) R. Greeff. "Ueber den Bau u. die Entwicklung d. Echinodermen." Sitz. d. Gesell. z. Beförderung d. gesam. Naturwiss. zu Marburg, No. 4. 1879.
(552) T. H. Huxley. "Report upon the researches of Müller into the anat. and devel. of the Echinoderms." Ann. and Mag. of Nat. Hist., 2nd Ser., Vol. VIII. 1851.
(553) Koren and Danielssen. "Observations sur la Bipinnaria asterigera." Ann. Scien. Nat., Ser. III., Vol. VII. 1847.
(554) Koren and Danielssen. "Observations on the development of the Starfishes." Ann. and Mag. of Nat. Hist., Vol. XX. 1857.
(555) A. Kowalevsky. "Entwicklungsgeschichte d. Holothurien." Mém. Ac. Pétersbourg, Ser. VII., Tom. XI., No. 6.
(556) A. Krohn. "Beobacht. a. d. Entwick. d. Holothurien u. Seeigel." Müller's Archiv, 1851.
(557) A. Krohn. "Ueb. d. Entwick. d. Seesterne u. Holothurien." Müller's Archiv, 1853.
(558) A. Krohn. "Beobacht. üb. Echinodermenlarven." Müller's Archiv, 1854.
(559) H. Ludwig. "Ueb. d. primar. Steinkanal d. Crinoideen, nebst vergl. anat. Bemerk. üb. d. Echinodermen." Zeit. f. wiss. Zool., Vol. XXXIV. 1880.
(560) E. Metschnikoff. "Studien üb. d. Entwick. d. Echinodermen u. Nemertinen." Mém. Ac. Pétersbourg, Series VII., Tom. XIV., No. 8. 1869.
(561)[233] Joh. Müller. "Ueb. d. Larven u. d. Metamorphose d. Echinodermen." Abhandlungen d. Berlin. Akad. (Five Memoirs), 1848, 49, 50, 52 (two Memoirs).
(562) Joh. Müller. "Allgemeiner Plan d. Entwicklung d. Echinodermen." Abhandl. d. Berlin. Akad., 1853. (563) E. Selenka. "Zur Entwicklung d. Holothurien." Zeit. f. wiss. Zool., Bd. XXVII. 1876.
(564) E. Selenka. "Keimblätter u. Organanlage bei Echiniden." Zeit. f. wiss. Zool., Vol. XXXIII. 1879.
(565) Sir Wyville Thomson. "On the Embryology of the Echinodermata." Natural History Review, 1864.
(566) Sir Wyville Thomson. "On the Embryogeny of Antedon rosaceus." Phil. Trans. 1865.
[233] The dates in this reference are the dates of publication.
ENTEROPNEUSTA.
(567) A. Agassiz. "Tornaria." Ann. Lyceum Nat. Hist. VIII. New York, 1866.
(568) A. Agassiz. "The History of Balanoglossus and Tornaria." Mem. Amer. Acad. of Arts and Scien., Vol. IX. 1873.
(569) A. Götte. "Entwicklungsgeschichte d. Comatula Mediterranea." Archiv für mikr. Anat., Bd. XII., 1876, p. 641.
(570) E. Metschnikoff. "Untersuchungen üb. d. Metamorphose, etc. (Tornaria)." Zeit. für wiss. Zool., Bd. XX. 1870.
(571) J. Müller. "Ueb. d. Larven u. Metamor. d. Echinodermen." Berlin. Akad., 1849 and 1850.
(572) J. W. Spengel. "Bau u. Entwicklung von Balanoglossus." Tagebl. d. Naturf. Vers. München, 1877.
CAMBRIDGE: PRINTED BY C. J. CLAY, M.A. & SON, AT THE UNIVERSITY PRESS
Transcriber Notes:
Punctuation, hyphenization, and accent marks were standardized. Missing letters were added, as appropriate. Words in italics are displayed between underscores, like this.
Consistently misspelled words (e.g. hydrophillia) were not changed.
Captions of some illustrations contain references to items not indentified in the illustration. The Greek letter, sigma, is spelled out in the caption to Figure 108. There is no Fig. 79 in the original.
Footnotes were renumbered sequentially and moved to follow the paragraph in which the anchor occurs. Anchors [64] and [65] refer to the same footnote.
Illustrations and captions were indented and placed within brackets.
Other changes:
- 11 instances of 'Müller's Archiv' to 'Müller's Archiv' - 8 instances of 'develope(s)' to 'develop(s)' - 'usally' to 'usually' ... there is usually found in young ... - 'occurrs' to 'occurs' ... It occurs in ... - 'investigagation' to 'investigation' ... a thorough investigation ... - 'cillated' to 'ciliated' ... the already ciliated ... external layer - 'on' to 'of' ... development of the type of Desor ... - 'intances' to 'instances' ... In some instances a more or less ... - 'natica' to 'nautica' ... a nautica-like shell,... - 'valves' to 'halves' ... The two halves rapidly grow ... - 'Natica' to 'Nautica' ... e.g. Nautica.... - 'suceeding' to 'succeeding' ....the three succeeding pairs,... - 'espcially' to 'especially' ... especially in the armature ... - 'pecularities' to 'peculiarities' ... marked peculiarities of ... Fig. 102 caption - 'Fom' to 'From' ... (From Gegenbauer ... Fig. 162 caption - 'sc.' to 'se.' to match illustration Fig. 253 caption - 'Pentracrinoid' to 'Pentacrinoid' Reference (95) - 'Wirbelthiereie' to 'Wirbelthiere' References (58) (59) (60) (95) (242) - 'micr.' to 'mikr.'