The aquarian naturalist : a manual for the sea-side

Front matter

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Preface

Our lamented friend the late Hugh Miller, in his delightful work “The Cruise of the Betsy,” surmises that some parties might have thought the geological chapters of the volume more entertaining if all the geology had been left out ; and yet, even with such an authority before us, we flatter ourselves that, in a work written pro¬ fessedly on the subject of the Marine Aquarium, a sketch of the Natural History of its inmates will be considered at least not misplaced.

In the following pages we have collected the principal facts connected with the ascertained habits and oeconomy of various races of animals inhabiting our own shores, with a view of direct¬ ing the attention of the amateur naturalist to subjects most likely to afford materials for useful and instructive observation, and likewise in the

VI

PREFACE.

hope of supplying the student of Nature with a manual sufficiently comprehensive to serve as the basis and foundation of more elaborate research. In the treatment of our subject, we have sought, as far as possible, to steer a middle course between the two extremes of mere elementary shallowness on the one hand, and scientific tech¬ nicality on the other ; omitting, it is hoped, little that will be deemed of importance by the general reader, and at the same time studiously avoiding such details as might be unintelligible, except to the initiated. We have endeavoured, in short, to comply as far as possible with the requisition of our lady-friends, — to write as much as possible about what they do want to know, and as little as possible about what they do not want to know. How far we have succeeded in our task, we leave to their merciful consideration.

Athenaeum Club,

Chapter I. Introductory

A sea-side sketch. — The calm. — The storm. — Changing aspects of the sea. — Use of storms. — Application of the facts ob¬ servable in Nature. — Form of aquarium. — Artificial rockwork. — Floor of the tank. — Pestiferous deposit. — Natural sea- water. — Artificial sea- water — how prepared for the aquarium by Mr. Gosse. — Proportions recommended by Mr. Warington. — Salts procured by evaporation. — Specific gravity of sea-water. — Vegetation proper for the tank. — Mr. Warington’s coloured media. — Vegetation not always essential. — Scavenger department. — Overcrowding to be avoided. — Assortment of specimens. — Management of light and temperature. — Precautions to be observed. — Artificial aeration of the water . p. 1-27

CHAPTER V. ON MEDUSiE, OR (( JELLY-FISHES.”

How to catch Medusae and submit them to microscopic exa¬ mination. — Habits of the Medusae. — Their property of sting¬ ing. — Luminosity of the Medusae. — Cause of their phospho¬ rescence. — Their unfitness for manure. — Account of a mon¬ ster. — Description of Turns neylecta. — Stomobrachium octoeostatum described by the Rev. D. Landsborough. — Sarsia gemmifera produces progeny from buds. — Reproduction of Sarsia jjrolifera . p. 52-07

Chapter XIV. Campanularian Zoophytes

IIow distinguishable from the Sertularian races. — History of Campanularia dichotoma. — Medusiparous reproduction. — Re-

X

CONTENTS.

searches of Sir John Dalyell. — Van Beneden’s observations, and hypothesis concerning the transformation of Medusoids into Polyps . p. 128-134

Chapter XV. Caryophyllia

Zoophytes until recently believed to be vegetables. — First glimpses of their real nature. — Peyssonnel. — Jussieu’s specu¬ lations. — Ideas of Henry Baker — Ellis. — History of Caryophyllia Smithii. — Formation of Coral islands. — Varieties of Coral reefs. — Elevation and subsidence of land. — Prodigious extent of Coral formations. — Succession of species of Coral Zoophytes . p. 135-149

Chapter XVI. Actiniae

How to procure Sea- Anemones. — General habits of the Actiniae ; their voracity and power of fasting ; adhesive and stinging properties. — Senses of the Actiniae ; capability of repairing injuries. — Dicquemare’s experiments. — Reproduction of Ac¬ tinia mesembryanthemum. — Propagation of Actinia lacera and Actinia dianthus by spontaneous separation of fragments. — Precautions to be observed in rearing Actiniae. — Unrefined habits of some species. — Actiniae used as food. . . p. 150-1(57

Chapter XVII. Lucernaria Campanulata

Description of the zoophyte. — Habits of Lucemaria. p. 1G8-1G9

Chapter XVIII. Encrinites — Comatula

Sermons in stones. — Encrinitic marble. — St. Cuthbert’s beads. — Elaborate structure of fossil Encrinites. — Pentacrinus Briareus . — Pentacrinus Europceus. — Rarity of living Encrinites. —

CONTENTS.

XI

Structure and mode of growth. — Comatula ; its organization and habits. — Pentacrinus the young of Comatula — a brittle subject for the aquarium . p. 170-18G

Chapter XX. Ophiurus — “ The Plate-mail Star-fish.”

Alarm amongst the Cockatoos. — Illustrations of instinct ; true and false. — Structure of Ophiurus. — History of PI uteus para¬ doxus. — Transformation of Pluteus. — Ophiocoma. p. 192-200

Chapter XXI. Asterias — “the Cross-fish.”

Habits of the Northern Sea-star.' — How Star-fishes eat oysters. — Habit of casting off their rays. — Renovation of mutilated Star-fislies. — Fisherman’s blunder. — A sea-side breakfast. — Disappointment. — Importance of Star-fishes in creation ; their treatment in the aquarium ; suicidal propensities. — “Eyes” and “eyelids” of the Star-fislies. — Eggs of the Star-fish. — Development of young Asterias . p, 201-213

Chapter XXII. Echinus — “ Sea-urchin.”

Origin of name. — Shell of Echinus esculentus. — Wonderful com¬ plexity of structure. — Necessity for such contrivance. — How the shell grows. — Ambulacral plates. — Suckers and loco¬ motive spines. — Food of the Sea-urchins. — Teeth of the Echinus. — “Lantern of Aristotle.” — Roe of the Sea-egg. — Le stufe di Xerone. — A delightful bathe. — Eggs, Pluteus, and metamorphosis of Echinus. — Pedicellarne. — Reparation of injuries . p. 214-238

Xll

CONTENTS.

Chapter XXIII. Holothuria — “ Sea-cucumber.”

A shipwreck. — A “ sea-pudding.” — Description of Hobthuria pentactes. — Locomotive suckers of Holothuria. — The “Nig¬ ger” or “Cotton-spinner.” — Habits of Holothurioe. — Holotli urine used as food. — Trepang-fishery. — Extraordinary powers of evisceration. — Regeneration of lost parts. — Capa¬ bility of spontaneous division. — Spawning and development of embryo . p. 234-249

CHAPTER XXXI. TEREBELLA LITTORALIS, SeU AREN ARIA — “ THE SAND MASON.”

Habits of Terebella — mode of constructing its tube — struc¬ ture of tentacula — elegant structure of branchiae — their eggs — structure of embryo. — Development of young Terebella — progressive growth. — Terebella Jigulus, “the Potter.” — Terebella conchilega, “the Shell -binder ” — its process of tube-building. — Terebella textrix, “the Weaver.” — Amphi¬ trite ostrearia . p. 288-306

Chapter XXXII. Nereides.*

Poetry fairly outdone by Nature. — General structure of the Nereids. — Eunice gigantea. — Habits of the Nereids. — Defen¬ sive and offensive weapons. — Strangely-constructed mouth. — Their means of sensation. — Remarkable mode of multipli¬ cation. — Nereis fulgens, “the Iridescent Nereis.” — Nereis ( Nephthys ) margaritacea. — Phglluduce laminosa, “Laminated

b

XIV

CONTENTS.

Nereis.” — Reproductive powers of Phyllodoce. — Nereis noctiluca , “the Glow-worm Nereis.” — Metamorphoses of the Nereids . p. 307-326

Chapter XLI. Pinnotheres — Talitrus— Corophium, Etc

Pinnotheres veterum, the Pea-crab — “ the Pinna and her Cancer friend.” — Habits of Pinnotheres. — Sea-spiders. — Isopod and Amphipod Crustaceans. — Long-horned Corophium. — Tube¬ making Crustaceans. — A word in favour of Natural History.

CHAPTER XLH.

CIRRIPEDES OR BARNACLES.

Natural History in the sixteenth century. — Old Gerrard. — Supposed origin of Barnacle Geese. — Lepades and Balani. — Pood of the Cirripedes. — Singular mode of fishing. — Propaga¬ tion of Lepades. — Appearance of nascent Cirripedes. — Meta¬ morphoses. — Barnacle neither a duck-egg nor a gosling.

Chapter XLIII. Wii1tby

Legends of St. Hilda. — Whitby Abbey. — A Zones of the ocean .

XVI

CONTENTS.

Chapter XLIV. Polyzoa (bryozoa, Ehrenberg) — Ascidian Polypes

The tangle-tliatched reef. — Habits of the Polyzoa. — Derivation of their name. — How to view Polyzoa under the microscope. — Mechanism of expansion and retraction. — Structure of tentacula. — Internal ceconomy. — Power of reproduction.

CHAPTER XLV. EOLIACEOUS AND INCRUSTING POLYZOA, FLUSTRiE, ESCIIARiE

ETC.

A delightful walk. — Flustroe, or Sea-mats. — Eschar as. — Popu¬ lation of Flustra membranacea. — Structure of Flustra hispida. — Reproduction by gemnmles. — Progressive addition of new cells . p. 418-426

CHAPTER XL VI.

ALCYONIDIUM GELATINOSUM — “ PUDDING-WEED ” —

“SEA RAGGED-STAFF.”

Philosophy of the sixteenth century. — Lord Bacon. — Ambrose Pare. — Unicorn’s horn. — Hooke. — Theory of pearl-diving. — Structure of Alcyonidium gelatinosum. — Reproduction by gemmules. — Innumerable progeny . ■ . p. 427-435

CHAPTER XL VII.

polyzoa continued — “ avicularia ” — “ vibracula,” etc.

Bugida avicularia. — Structure of “ avicularium.” — Probable office of the “ Bird’s-heads.” — Structure and functions of “ vibracula.” — Distribution of the Polyzoa . p. 436-442

CHAPTER XL VIII.

TUNICATA — ASCIDIANS.

A stormy day. — General description of Ascidians. — Forms of simple Ascidians. — Organization of simple Ascidians. — Re-

CONTENTS.

XVII production. — Metamorphosis of “ Spinula.” — Cynthia aggregata. — Cynthia ampulla. — Ascidia intestinalis . p.443-452

CHAPTER XLIX.

COMPOUND ASCIDIANS.

Composition of colony. — Metamorphosis. — How Compound Ascidians become associated. — Pyrosoma . p. 453-460

CHAPTER L. salp^:.

Alternation of generations. — Organization and habits of Salpse. — Phosphorescence . p. 461-464

CHAPTER LI.

THE SCALLOP-SHELL, THE MUSSEL, AND THE LIMA.

Structure of the Scallop. — Ciliated branchiae. — Faculty of loco¬ motion. — Fabrication of byssus. — Habits of Lima tenera.

CHAPTER LII.

SOLEN SILIQUA — “ THE RAZOR-SHELL.”

Excursion with Sir John Ross. — Mode of fishing for the Razor-shell. — Uses of the u foot.” . p.477-484

CHAPTER LIII.

PHOLAS DACTYLUS.

Boring bivalves. — Structure of siphons. — How the rock is per¬ forated. — Phosphorescence of Pholades. — Prodigious fertility of the Conchifera . p. 485-493

CHAPTER LIV.

GASTEROPOD MOLLUSCA.

A remonstrance. — Foot of Gasteropods. — Aplysia, u the Sea-hare.” — A suspicious character. — Food and habits of Aplysia.

.Will

CONTENTS.

— Proboscis of carnivorous Gasteropods. — Eggs of carni¬ vorous Gasteropods. — Oothecae of Buccinum ; of Fusus antiquus ; of Nassa reticulata ; of Natica ; of Purpura. — Eggs of the Ceplialopods or Cuttle-fishes. — Chitons. — Nudibranchiate Gasteropods. — Doris. — Spawn of Doris tuberculata. — Metamorphoses — “Nautilinos.” — Eolis. — Reproduc¬ tion and habits of Eolis . p. 494-512

CHAPTER LV.

PISHES : — AMPHIOXUS — ECHENEIS — SYNGNATHUS. —

Conclusion

The Lancelot, — Echeneis Remora, — its fabulous attributes. — Syngnathidae. — Habits of Syngnatlius Hippocampus. — Con¬ clusion . p. 513-524

PLATE I. (Frontispiece.)

Sponge.

Page

Fig. 1. Circulation and gemmules of tlie Sponge ( Spongia papillaris). a. Section of the

living sponge, h. Gcmmule magnified, show¬ ing the cilia . 30

Fig. 2. Nonionina Germanica. a. The same after

the dissolution of its shell by means of acid . 39

Fig. 3. Noctiluca . 49

Fig. 4. Medusa chrysaora (Dalycll) . 78

Fig. 5. Hydra tuba . G8

Fig. 7. Sarsia gemmifera . 65

Fig. 8. Stomobrachium octocostatum. Seen from

below . G4

Fig. 9. Stomobrachium octocostatum. Lateral view. G4

Fig. 10. CYDirPE pomiformis. a. Newly extruded egg.

b, c, d , e. Progressive development of the embryo . 97

Fig. 11. Cyanea chrysaora. Upper surface . 57

Fig. 12. Cyanea chrysaora. Seen from below .... 57

THE

AQUARIAN NATURALIST.

MARINE ANIMALS.

CHAPTER I. Fond man ! yon glassy mirror eye

Go, pierce the flood, and there descry The miracles that float between The rainy leaves of watery green ;

Old Ocean’s hoary treasures scan ;

See nations swimming round a span. — Crabbe.

INTRODUCTORY.

Who among us but remembers with pleasurable emotion those happy days, when, with a boyish rod and line, we caught our first minnows hi the way-side brook, and the delight with which we landed on the grass our tiny victims — the deep regret with which we saw them die, and all their splendid colours fade ? Who forgets, when, with an effort to preserve the pretty dwellers in the stream, he next appeared, bottle in hand filled with clear water, and essayed to take them home alive and see them swim in their impri¬ sonment, gazing with rapture on their silvery hues and

B

THE AQUARIAN NATURALIST.

active movements, — hoping all the time — vain hope ! — to keep them as his own ? An hour or two, and they were floating on their hacks, gasping their little lives away in helpless agony !

Or in maturer years, when visiting the shores of the wide Sea in search of health or for amusement, who amongst us has not yearned to keep alive and make his own the countless lovely objects that surround his path ; and, as they wtoo his admiration, seem to court his care in order to preserve their fading beauties ? How often has he tried, in vessels tilled with their native element, to rear them ; but has seen them die in spite of all his efforts, melt away before his eyes, and,

u ... . like tlie baseless fabric of a vision,

Leave not a wreck behind ! ”

Should he ask himself why he thus fails, the simple answer is, he did not change the water, and they died.

It is a lovely morning; let us stroll awhile upon the shingly beach and watch the ebbing tide. How stealthily the sea retires ! — each gently curtseying wave, as its last ripplings sink upon the sand, leaving a line of foam to show how far it had presumed to come. The rocks are now laid bare, over whose weed-crowned heads the gentle spray is tossed in feathery wreaths, which, sparkling in the sunbeams, shine with all the rainbow’s hues, until the sinking waters leave the limpet-covered crags in silent loneliness. We climb their slippery sides, and sit us down beside some rock-girt pool, whose tranquil surface, stirless as a glass, permits us to survey the depths below, clear and translucent. Sea- weeds of roseate hues and forms

USE OF STORMS.

more delicate tlian those of earth, in rich profusion clothe the sides and bottom ; others of varied dyes, purple and green, hang loosely floating in the quiet depths ; pensile Confervas wave from every stone — a wilderness of vegetation. Interspersed with these, the jointed Corallines spread forth their stony branches, and Sea-flowers of every colour, opening to the sun, unfold their living petals to entrap their food. The glassy shrimps and prawns are faintly seen, lost in their own transparency ; and little fishes darting here and there, or poised with quivering fins, give life and animation to the scene.

The sun becomes obscured, and the breeze freshens from the sea ; dark clouds are gathering on the hori¬ zon, and the tide begins to turn ; the heaving waves now tumble towards the shore, and as they break, in angry foam, portend a storm. The sky looks threat¬ ening, and the thunder growls far in the distance. The sea awakens as from slumber, and the blackening heavens lour over its dark bosom; while the rising blast, impelling all the waves, drives them upon the rocks in sheets of feathery foam, lashing them on to madness, till at length ocean and sky seem mingled. The raging winds now

“ . take the ruffian billows by the tops,

Curling their monstrous heads, and hanging them AVith deafening clamours in the slippery clouds

from whence they fall into the yeasty depths, where all is violence and roar and rage.

Such are the changing aspects of the Sea, and such the efficient means whereby Nature ensures the reno¬ vation of that element, the mighty deep, the grand

THE AQUARIAN NATURALIST.

antagonist of all the earth — refreshing it throughout its broad domains, keeping its waters wholesome — filled with air, and thus adapted to afford the means of respiration to the living things that flourish in its vast recesses. It is evident, that it is only by imitating the conditions observable in Creation that we can ever hope to succeed in our attempts at keeping alive and in health for any lengthened period animals that we desire to preserve in our Vivaria, and it is not difficult for the observant mind to perceive how those conditions are to be fulfilled. Water itself, while in a stagnant state, affords no air such as can be respired by any animal. To fill it then with atmospheric air, or oxygen , the purer element, must be the first essen¬ tial ; secondly, to keep it stored with food adapted to the nourishment of those creatures that we place in it, is as imperatively requisite. The storms that tempest ocean, “ making the sea to boil like a pot,” effect the former condition by commingling the air of the atmosphere with the waters of the sea. The vegeta¬ tion which clothes the rocks and carpets the shallows, or floats through every region, when exposed to sun¬ shine, as we all well know, pours forth oxygen gas in abundance sufficient to replace that which is con¬ sumed by respiration, and moreover yields such ample stores of food as will supply all the vast hunger of the mighty deep. With these two grand facts before us, it is manifest upon what principles an Aquarium ought to be established ; how those principles may be put in practice must be the next object of our inquiry.

It is easy to enunciate a broad fact ; but the appli¬ cation of it is a ver\' different thing. Mankind knew

FORM OF AQUARIUM.

P0

Jong ago the expansive force of steam ; but it required the united genius of many mighty minds to realize the steam-engine. The facts above narrated have been long enough sufficiently well known ; but we are indebted to the patient inquiries of Mr. Warington and Mr. Gosse for those practical instructions, which introduced into our drawing-rooms the most elegant productions of the ocean, and enabled the student of Creation, at his own fireside, to carry out observa¬ tions of deep importance, both to the Natural His¬ torian and the Physiologist, which heretofore were scarcely possible even on the seashore. It is to these gentlemen, therefore, we must principally have re¬ course for information as to the manner in which our Aquaria should be constructed and prepared.

The form of aquarium which, after some years’ experience and observation on the various animated tenants of these miniature seas, Mr. Warington has now adopted, consists of a four-sided vessel, having the back gradually sloping upwards from the bottom, at an angle of 45 to 50 degrees, and the consequently extended top sloping slightly downwards, and resting on the upper part of the back. The bottom therefore becomes necessarily narrow. The front, for the pur¬ poses of observation, and the top, for the admission of light, are of glass ; the back, ends and bottom being constructed of slate, the whole fixed in a stout framework.

The advantages of this arrangement are, —

First, that it allows of a most extended view of the whole interior of the aquarium.

Secondly, that it enables the occupants to resort to

THE AQUARIAN NATURALIST.

any depth they may desire, or even to ascend the sloping back and emerge from the water.

Thirdly, it admits of a much larger surface being exposed to the action of light ; and,

Fourthly, the sloping top allows the water which condenses on the glass to trickle off and return to the aquarium, without first resting on the zinc or iron framework. It need hardly be suggested, that the •sloping back is to be covered with light rock- work extending to a short distance above the water-line.

Let it not, however, be supposed, that although the form of tank above described by Mr. Warington may be the best in its general construction, it is by any means indispensable ; tanks of all shapes and sizes are now to be readily procured at moderate prices adapted to all tastes. Yet even these are luxuries : a common show-glass, such as we see in confectioners* shops, a large glass gold-fish globe, or, in default of these, a common earthenware pan will be found to answer every end — as far, at least, as relates to the preservation of specimens for the pur¬ poses of scientific research.

The common propagating glasses used by gardeners, and which may be procured of almost any size, form admirable substitutes for the more expensive plateglass tank; and the broad shallow glass pans now generally in use for holding milk, will be found in many cases even more convenient than deeper vessels. They say that it is only the bad workman who finds fault with his tools, and upon the same principle the real naturalist will never be at a loss for an appropriate vessel as long as a dish or a basin can be obtained.

ARTIFICIAL ROCK-WORK. 7

Iialf-a-dozen finger-glasses, such as are generally placed upon tlie table after dinner, will be found in¬ valuable, and for containing small specimens, adapted to microscopical examination, even preferable to vessels of larger size. Let one of these be filled tliree-parts full of fresh and pure sea- water — strew the bottom with a few small stones and bits of rock, on which are growing Confer vae and young Sea- weeds in a state of vigorous growth, and you at once have an aquarium fitted for the reception of an infinite variety of in¬ teresting objects. Hydrae and Corynae, Sertularian and Tubularian Zoophytes, Crisiae, Bowerbankiae, and the whole host of Polyzoa, the delicate Tubularia, and the many-polyped Antliozoa, here grow luxuriantly, and may be kept for months under examination.

In the arrangement of a large tank, one of the most important features to be attended to is the in¬ troduction, upon a miniature scale, of rock-work, whereby the surface for the growth of plants may be most materially increased, and a picturesque appear¬ ance given to the aquarium, which could not possibly be attained without such an expedient. A wide field is here opened for the display of taste and ingenuity ; it is a piece of landscape gardening upon a small scale, on which every amateur may exercise his talents with advantage, always keeping in view the various uses to which the miniature rockery ought to be subservient. The first of these, as we have already said, is to increase the superficial extent of the interior of the aquarium, and present a larger surface for the growth of vegeta¬ tion, a circumstance of primary importance in the arrangement ; for, as we shall shortly perceive, the

THE AQUARIAN NATURALIST.

entire superficies of tliese rocks speedily becomes in¬ vested with a dense vegetable growth, itself sufficient to aerate and keep in a healthy condition the entire contents of the aquarium, even without the introduc¬ tion of plants of more conspicuous character; every stone in time becomes covered with a thick and moss¬ like carpet, from whence, in the sunshine, bubbles of oxygen may be seen to stream in copious abundance, and almost rendering other care unnecessary. A second important use derivable from the rock-scenery we are here recommending, is the provision of shelter and secure retreat for such animals as may require an asylum. We ought always to bear in mind, that the more nearly we can imitate the usual habitat of our protegees, the more successful will be our efforts to pre¬ serve them in a healthy condition. A little reflection will at once teach us, that to seek retirement and se¬ clusion, except at certain times of the day, is with many animals an imperative instinct, a law of their economy that cannot be broken without producing injurious effects. It is therefore desirable so to dispose our materials as to leave caves and crannies and hidingplaces, whereunto animals requiring such protection may betake themselves.

Shade likew ise is a desideratum of no triflimr importance : constant or even prolonged exposure to the full glare of daylight must necessarily prove pre¬ judicial to animals that frequent the umbrageous pools, or delight in the seclusion of dimly-illuminated corners of their native localities. In the construction of our rock-work, therefore, this point should by no means be lost sight of.

FLOOR OF TIIE T.WK.

It is always best to build up the rock-work with loose stones, placed upon the bottom of the tank — arranging them in such a manner, that not only shelter, shade, &c., may be afforded to the contained animals, but that they may be enabled to station them¬ selves at any depth in the water which their habits or choice may lead them to select.

The best materials for this purpose will be found to be pieces of granite or of limestone of various shapes and sizes ; but all of such weight and regularity of form, that, when placed one upon the other, in ac¬ cordance with the taste or intention of the designer, they may rest firmly and securely in their respective places. No cement should be employed in the con¬ struction of these mimic edifices ; their weight alone and steady supraposition upon each other should ensure the firmness and stability of the entire fabric.

Rude bridges of Cyclopian masonry — edifices some¬ what after the pattern of Stonehenge and other Celtic piles — caverns of wave-worn rock and craggy terraces — should rise above each -other, till the top, reaching above the level of the water, forms a little island of drv land.

We will, however, now confine our attention to the permanent Aquarium, and the mode of its establish¬ ment. We suppose the rock- work to have been ar¬ ranged in accordance with the shape and dimensions of the tank, and scars and reefs, and cliffs and caves, to be adequately represented without needlessly oc¬ cupying the valuable space in the interior.

The next step, of course, is to lay down the bottom of our miniature sea, so as to adapt it to the comfort b o

THE AQUARIAN NATURALIST.

and well-being of its intended inhabitants. Here (and the arrangement is of considerable importance) we must study Nature. The floor should be composed of smooth washed shingle, the stones resembling in size a pea, a bean, up to a hazel-nut, as a substratum ; but with, here and there, a larger piece, whose bulk, like Skiddaw or Helvellvn, so to compare great things with small, may protrude through the alluvial plain to be deposited above. Upon the top of this, a stratum of fine sand (sea-sand) should be spread to the depth of at least three-quarters of an inch or more.

The uses of this sea-sand are, in some measure, as we shall find hereafter, important in relation to many species of marine animals that hide themselves under its shelter, or derive from it the materials wherewith to build their habitations ; but at present we must regard it in its Hygeian character, in so far as it is important to the maintenance of the health of the entire community.

V

Whoever upon the sea- shore takes the trouble to dig to the depth of a few inches, more or less, according to the peculiar circumstances of the locality, will find beneath the clean and wholesome sand a layer of black, or bluish, paint-like, stinking slime, the dregs and filth deposited, as it were, by filtration. Any one who has stood upon the beach where the receding tide, by washing away the surface-sand, and laying bare this foul accumulation, has thus stirred up the abominable odours of the Stygian pool, can vouch for the deleterious effluvia that ema¬ nate from this pestiferous deposit, which, were it not thus safely buried, would poison the entire coast, and

NATURAL SEA-WATER.

render the shores uninhabitable. The naturalist ought therefore to be very cautious how he allows the bottom of an old-established tank to be disturbed ; still more so in permitting the casual introduction of any shell or stone into his aquarium that is polluted with this noisome pestilence. We have ourselves lost many valuable colonies owing to the imprudent zeal of friends, who, in their anxiety to add some new¬ found specimen to our stock, have neglected thoroughly to cleanse the shell, or pebble upon which it was at¬ tached, from the adherent filth.

To procure a supply of sea-water adapted to the purposes of the Aquarium is the next consideration ; and simple as this part of the business may appear, it is by no means always an easy matter even to parties resident upon the sea-shore. On certain favoured beaches, it is true, nothing more is requisite than to take a watering-can to the water's edge, and fill it from the brimming ocean ; but this is unfortunately rather an exceptional privilege. On most of our coasts, too, it generally happens, that during both the advancing and receding tide, the muddy shore, stirred up by the incessant turmoil of the waves, pollutes the sea to such an extent that it is quite inadmissible into the tank. So that the naturalist, like the poor thirstparched mariner, with

“ Water, water, all around,

And not a drop to drink ! ”

eyes the expanse of dirty waves in a state of hope¬ less tantalization. In such a case, the oidy chance is to procure a boat, and obtain^ at a sufficient

THE AQUARIAN NATURALIST.

distance from the shore, a cargo from the clear green billow.

The clement wherein the captives are kept should be always sweet and quite clear; the vessels clean, and free from tainted matter. Some specimens fall immediate victims to putrescence ; others can resist it wonderfully, either endeavouring to escape by ascent or by descent, according to their peculiar nature, or closing themselves up, as if to avoid its deadly influence. The water for most of the Crustacea should be free from mud, and contain eminences whereon they may rest, at will, above the surface. But muddy solutions are essential to most of the bivalve Testacea, and to all the Ascidian tribes ; a certain proportion of mud is likewise grateful to several Amphitrites, and to many Annelidans, as sand is to the various species of Nereis.

An excellent test whereby to judge of the purity and wholesome condition of the water may be esta¬ blished by the simple introduction of a few living specimens of the Acorn-shell or Barnacle ( Lepas ), which are to be found abundantly, adherent to stones or shells, on any part of the coast. Whilst these continue active and healthy, as testified by the ener¬ getic display and contraction of their delicate and highly sensitive arms, we may rest quite satisfied that all is going on well ; but, on the other hand, their inactivity ought to call attention to the condition of the tank.