Chapter I: Front Matter (1)

TRANSCRIBER’S NOTE

Italic text is denoted by _underscores_.

Footnote anchors are denoted by [number], and the footnotes have
been placed at the end of the book.

Chapter headings have been made consistent, with the title on a
single line and the author on the following line.

The Index in this book covers all four volumes.

Some minor changes to the text are noted at the end of the book.

Volume I of this set of four volumes can be found in Project
Gutenberg at: https://www.gutenberg.org/ebooks/74571

Volume II can be found in Project Gutenberg at:
https://www.gutenberg.org/ebooks/77792

Volume III can be found in Project Gutenberg at:
https://www.gutenberg.org/ebooks/77827

1, Callimorpha; 2, Prionus Cervicornus; 3, 6, Licæna; 4. Oryctes Hercules; 5, Lucanus Cervus; 7, Zeryntina; 8, Lithosia; 9, Arctia; 10, Cynthia; 11, Papilio Œnora; 12, Oryctes Nasicornis; 13, Melolontha; 14, Papilio Machaon; 15, Goliathus; 16, Ditiscus; 17, Leptura; 18, Geotrupes; 19, 20, Vanessa; 21, Urania]

THE STORY OF
THE UNIVERSE

_Told by Great Scientists
and Popular Authors_

COLLECTED AND EDITED

_By_ ESTHER SINGLETON

Author of “Turrets, Towers and Temples,” “Wonders of Nature,”
“The World’s Great Events,” “Famous Paintings,” Translator
of Lavignac’s “Music Dramas of Richard Wagner”

_FULLY ILLUSTRATED_

VOLUME IV

THE
EARTH’S
CREATURES:
FAUNA

THE CURRENT LITERATURE
PUBLISHING CO.,
NEW YORK

COPYRIGHT 1905
P. F. COLLIER & SON

ILLUSTRATIONS

Butterflies and other Insects _Frontispiece_

Radiolaria _Opposite p._ 1327

Curious Zoophytes ” 1375

Fishes ” 1423

Shells ” 1495

Types of Extinct Fishes, Shells, and Crustacea ” 1543

Birds ” 1591

Fairy Flies ” 1639

American Reptiles ” 1687

CONTENTS

OMNIPRESENCE OF LIFE. George Henry Lewes 1285

THE ANIMAL KINGDOM. Thomas H. Huxley 1296

THE FOUR CLASSES. Baron Cuvier 1301

DEEP SEA FAUNA. Lord Kelvin 1304

“THE MIMIC FIRES OF OCEAN.” G. Clarke Nuttall 1320

THE JELLY-FISH AND OTHER HYDROZOA. P. Martin Duncan 1324

FISHES. Andrew Wilson 1337

WONDERS OF THE SHORE. Charles Kingsley 1357

CRABS, PRAWNS, AND LOBSTERS. Philip Henry Gosse 1374

REPTILES. Peter Mark Roget 1379

THE CLASSIFICATION AND ORIGIN OF INSECTS. Lord Avebury 1401

INSECTS: THEIR WINGS, STINGS, EARS, AND EYES.
Philip Henry Gosse 1425

FAIRY FLIES. Fred. Enock 1449

INSECT TRANSFORMATIONS. Andrew Wilson 1458

STRUGGLE FOR EXISTENCE. Charles Darwin 1464

NATURAL SELECTION. Charles Darwin. 1482

MAMMALIA. Baron Cuvier 1513

ZOOLOGICAL ZONES. Sir Richard Owen 1520

GEOGRAPHICAL DISTRIBUTION OF ANIMALS. William Hughes 1535

CETACEA. Peter Mark Roget 1561

HUNTING AND FISHING OF ANIMALS. Frédéric Houssay 1565

THE DEATH-FEIGNING INSTINCT. W. H. Hudson 1577

BIRDS. J. Arthur Thomson 1582

MIMICRY. David Robertson 1593

DWELLINGS. Frederic Houssay 1601

MAN’S FIRST APPEARANCE. Boyd Dawkins 1647

MAN’S PRIMITIVE CONDITION. Duke of Argyl 1656

RACES OF MANKIND. Wiliam Hughes 1667

THE HUMAN RACE. Louis Figuier 1679

INDEX 1695

THE STORY OF THE UNIVERSE (VOLUME FOUR)

THE STORY OF THE UNIVERSE

OMNIPRESENCE OF LIFE
--GEORGE HENRY LEWES

Come with me, and lovingly study Nature, as she breathes, palpitates, and works under myriad forms of Life-forms unseen, unsuspected, or unheeded by the mass of ordinary men. Our course may be through park and meadow, garden and lane, over the swelling hills and spacious heaths, beside the running and sequestered streams along the tawny coast, out on the dark and dangerous reefs, or under dripping caves and slippery edges. It matters little where we go: everywhere--in the air above, the earth beneath, and waters under the earth--we are surrounded with Life. Avert your eyes a while from our human world, with its ceaseless anxieties, its noble sorrow, poignant, yet sublime, of conscious imperfection aspiring to higher states, and contemplate the calmer activities of that other world with which we are so mysteriously related. I hear you exclaim,

“The proper study of mankind is man;”

nor will I pretend, as some enthusiastic students seem to think, that

“The proper study of mankind is _cells_;”

but agreeing with you, that man is the noblest study, I would suggest that under the noblest there are other problems which we must not neglect. Man himself is imperfectly known, because the laws of universal Life are imperfectly known. His life forms but one grand illustration of Biology--the science of Life--as he forms but the apex of the animal world.

Our studies here will be of Life, and chiefly of those minuter or obscurer forms which seldom attract attention. In the air we breathe, in the water we drink, in the earth we tread on, Life is everywhere. Nature _lives_: every pore is bursting with Life; every death is only a new birth, every grave a cradle. And of this we know so little, think so little! Around us, above us, beneath us, that great mystic drama of creation is being enacted, and we will not even consent to be spectators! Unless animals are obviously useful or obviously hurtful to us, we disregard them. Yet they are not alien, but akin. The Life that stirs within us stirs within them. We are all “parts of one transcendent whole.” The scales fall from our eyes when we think of this; it is as if a new sense had been vouchsafed to us, and we learn to look at Nature with a more intimate and personal love.

Life everywhere! The air is crowded with birds--beautiful, tender, intelligent birds--to whom life is a song and a thrilling anxiety, the anxiety of love. The air is swarming with insects--those little animated miracles. The waters are peopled with innumerable forms, from the animalcule, so small that one hundred and fifty millions of them would not weigh a grain, to the whale, so large that it seems an island as it sleeps upon the waves. The bed of the seas is alive with polypes, crabs, star-fishes, and with sand-numerous shell-animalcules. The rugged face of rocks is scarred by the silent boring of soft creatures, and blackened with countless mussels, barnacles, and limpets.

Life everywhere! on the earth, in the earth, crawling, creeping, burrowing, boring, leaping, running. If the sequestered coolness of the wood tempt us to saunter into its checkered shade, we are saluted by the murmurous din of insects, the twitter of birds, the scrambling of squirrels, the startled rush of unseen beasts, all telling how populous is this seeming solitude. If we pause before a tree, or shrub, or plant, our cursory and half-abstracted glance detects a colony of various inhabitants. We pluck a flower, and in its bosom we see many a charming insect busy at its appointed labor. We pick up a fallen leaf, and if nothing is visible on it, there is probably the trace of an insect larva hidden in its tissue, and awaiting there development. The drop of dew upon this leaf will probably contain its animals, visible under the microscope. This same microscope reveals that the _blood-rain_ suddenly appearing on bread, and awakening superstitious terrors, is nothing but a collection of minute animals (Monas prodigiosa); and that the vast tracts of snow which are reddened in a single night owe their color to the marvelous rapidity in reproduction of a minute plant (Protococcus nivalis). The very mould which covers our cheese, our bread, our jam, or our ink, and disfigures our damp walls, is nothing but a collection of plants. The many-colored fire which sparkles on the surface of a summer sea at night, as the vessel plows her way, or which drips from the oars in lines of jeweled light, is produced by millions of minute animals.

Nor does the vast procession end here. Our very mother-earth is formed of the débris of life. Plants and animals which have been built up its solid fabric. We dig downward thousands of feet below the surface, and discover with surprise the skeletons of strange, uncouth animals, which roamed the fens and struggled through the woods before man was. Our surprise is heightened when we learn that the very quarry itself is mainly composed of the skeletons of microscopic animals; the flints which grate beneath our carriage wheels are but the remains of countless skeletons. The Apennines and Cordilleras, the chalk cliffs so dear to homeward-nearing eyes--these are the pyramids of bygone generations of atomies. Ages ago these tiny architects secreted the tiny shells which were their palaces; from the ruins of these palaces we build our Parthenons, our St. Peters, and our Louvres. So revolves the luminous orb of Life! Generations follow generations; and the Present becomes the matrix of the Future, as the Past was of the Present--the Life of one epoch forming the prelude to a higher Life.

When we have thus ranged air, earth, and water, finding everywhere a prodigality of living forms, visible and invisible, it might seem as if the survey were complete. And yet it is not so. Life cradles within Life. The bodies of animals are little worlds, having their own animals and plants. A celebrated Frenchman has published a thick octavo volume devoted to the classification and description of _The Plants which Grow on Men and Animals_;[1] and many Germans have described the immense variety of animals which grow on and in men and animals; so that science can boast of a parasitic Flora and Fauna. In the fluids and tissues, in the eye, in the liver, in the stomach, in the brain, in the muscles, parasites are found, and these parasites have often _their_ living parasites in them!

We have thus taken a bird’s-eye view of the field in which we may labor. It is truly inexhaustible. We may begin where we please, we shall never come to an end; our curiosity will never slacken.

“And whosoe’er in youth
Has through ambition of his soul given way
To such desires, and grasp’d at such delights,
Shall feel congenial stirrings late and long.”

As a beginning, get a microscope. If you can not borrow, boldly buy one. Few purchases will yield you so much pleasure; and, while you are about it, do, if possible, get a good one. Spend as little money as you can on accessory apparatus and expensive fittings, but get a good stand and good glasses. Having got your instrument, bear in mind these two important trifles--work by daylight, seldom or never by lamplight; and keep the unoccupied eye _open_. With these precautions you may work daily for hours without serious fatigue to the eye.

Now where shall we begin? Anywhere will do. This dead frog, for example, that has already been made the subject of experiments, and is now awaiting the removal of its spinal cord, will serve us as a text from which profitable lessons may be drawn. We snip out a portion of its digestive tube, which, from its emptiness, seems to promise little; but a drop of the liquid we find in it is placed on a glass slide, covered with a small piece of very thin glass, and brought under the microscope. Now look. There are several things which might occupy your attention, but disregard them now to watch that animalcule which you observe swimming about. What is it? It is one of the largest of the Infusoria, and is named Opalina. When I call this an Infusorium I am using the language of text-books; but there seems to be a growing belief among zoologists that the Opalina is not an Infusorium, but the infantile condition of some worm (Distoma?). However, it will not grow into a mature worm as long as it inhabits the frog; it waits till some pike or bird has devoured the frog, and then, in the stomach of its new captor, it will develop into its mature form--then, and not till then. This surprises you. And well it may; but thereby hangs a tale, which to unfold--for the present, however, it must be postponed, because the Opalina itself needs all our notice.

Observe how transparent it is, and with what easy, undulating grace it swims about; yet this swimmer has no arms, no legs, no tail, no backbone to serve as a fulcrum to moving muscles--nay, it has no muscles to move with. ’Tis a creature of the most absolute abnegations--sans eyes, sans teeth, sans everything; no, not sans everything, for, as we look attentively, we see certain currents produced in the liquid, and, on applying a higher magnifying power, we detect how these currents are produced. All over the surface of the Opalina there are delicate hairs in incessant vibration; these are the _cilia_.[2] They lash the water, and the animal is propelled by their strokes, as a galley by its hundred oars. This is your first sight of that ciliary action of which you have so often read, and which you will henceforth find performing some important service in almost every animal you examine. Sometimes the cilia act as instruments of locomotion; sometimes as instruments of respiration, by continually renewing the current of water; sometimes as the means of drawing in food, for which purpose they surround the mouth, and by their incessant action produce a small whirlpool into which the food is sucked. An example of this is seen in the Vorticella.

Having studied the action of these cilia in microscopic animals, you will be prepared to understand their office in your own organism.

It is an interesting fact, that while the direction in which the cilia propel fluids and particles is generally toward the interior of the organism, it is sometimes _reversed_, and, instead of beating the particles inward, the cilia energetically beat them back if they attempt to enter. Fatal results would ensue if this were not so. Our air-passages would no longer protect the lungs from particles of sand, coal-dust, and filings flying about the atmosphere; on the contrary, the lashing hairs which cover the surface of these passages would catch up every particle and drive it onward into the lungs. Fortunately for us, the direction of the cilia is reversed, and they act as vigilant janitors, driving back all vagrant particles with a stern “No admittance, _even_ on business!” In vain does the whirlwind dash a column of dust in our faces--in vain does the air, darkened with coal-dust, impetuously rush up the nostrils; the air is allowed to pass on, but the dust is inexorably driven back.

The swimming apparatus of the Opalina has led us far away from the little animal who has been feeding while we have been lecturing. At the mention of feeding you naturally look for the food that is eaten, the mouth and stomach that eat. But I hinted just now that this ethereal creature dispenses with a stomach, as too gross for its nature, and, of course, by a similar refinement, dispenses with a mouth. Indeed, it has no organs whatever except the cilia just spoken of.

And this leads us to consider what biologists mean by an _organ_: it is a particular portion of the body set apart for the performance of some particular function. The whole process of development is this setting apart for special purposes. The starting-point of Life is a single cell--that is to say, a microscopic sac, filled with liquid and granules, and having within it a nucleus, or smaller sac. Paley has somewhere remarked that in the early stages there is no difference discernible between a frog and a philosopher. It is very true--truer than he conceived. In the earliest stage of all, both the Batrachian and the Philosopher are nothing but single cells, although the one cell will develop into an Aristotle or a Newton, and the other will get no higher than the cold, damp, croaking animal which boys will pelt, anatomists dissect, and Frenchmen eat. From the starting-point of a single cell this is the course taken: the cell divides itself into two, the two become four, the four eight, and so on, till a mass of cells is formed not unlike the shape of a mulberry. This mulberry-mass then becomes a sac, with double envelopes or walls; the inner wall, turned toward the yelk, or food, becomes the _assimilating_ surface for the whole; the outer wall, turned toward the surrounding medium, becomes the surface which is to bring frog and philosopher into contact and relation with the external world--the Non-Ego, as the philosopher in after life will call it. Here we perceive the first grand “setting apart,” or _differentiation_, has taken place; the embryo having an assimilating surface, which has little to do with the external world, and a sensitive, contractile surface, which has little to do with the preparation and transport of food. The embryo is no longer a mass of similar cells; it is already become dissimilar, _different_, as respects its inner and outer envelope. But these envelopes are at present uniform; one part of each is exactly like the rest. Let us, therefore, follow the history of Development, and we shall find that the inner wall gradually becomes unlike itself in various parts, and that certain organs, constituting a very complex apparatus of Digestion, Secretion, and Excretion, are all one by one wrought out of it by a series of metamorphoses or _differentiations_. The inner wall thus passes from a simple assimilating surface to a complex apparatus serving the functions of vegetative life.

Now glance at the outer wall: from it also various organs have gradually been wrought; it has developed into muscles, nerves, bones, organs of sense, and brain--all these from a simple homogeneous membrane!

With this bird’s-eye view of the course of development you will be able to appreciate the grand law first clearly enunciated by Goethe and Von Baer as the law of animal life, namely, that development is always from the general to the special, from the simple to the complex, from the homogeneous to the heterogeneous, and this by a gradual series of _differentiations_.

Here is our Opalina, for example, without mouth, or stomach, or any other organ. It is an assimilating surface in every part; in every part a breathing, sensitive surface. Living on liquid food, it does not need a mouth to seize or a stomach to digest such food. The liquid, or gas, passes through the Opalina’s delicate skin by a process which is called _endosmosis_; it there serves as food; and the refuse passes out again by a similar process, called _exosmosis_. This is the way in which many animals and all plants are nourished. The cell at the end of a rootlet, which the plant sends burrowing through the earth, has no mouth to seize, no open pores to admit the liquid that it needs; nevertheless, the liquid passes into the cell through its delicate cell-wall, and passes from this cell to _other_ cells upward from the rootlet to the bud. It is in this way, also, that the Opalina feeds: it is all-mouth, no-mouth; all-stomach, no-stomach. Every part of its body performs the functions which in more complex animals are performed by organs specially set apart. It feeds without mouth, breathes without lungs, and moves without muscles. The Opalina, as I have said, is a parasite. It may be found in various animals, and almost always in the frog.

Nature is economic as well as prodigal of space. She fills the illimitable heavens with planetary and starry grandeurs, and the tiny atoms moving over the crust of earth she makes the homes of the infinitely little. Far as the mightiest telescope can reach, it detects worlds in clusters, like pebbles on the shore of infinitude; deep as the microscope can penetrate, it detects life within life, generation within generation, as if the very universe itself were not vast enough for the energies of life!

THE ANIMAL KINGDOM
--THOMAS H. HUXLEY

As soon as the labors of anatomists had extended over a sufficiently great variety of animals, it was found that they could be grouped into separate assemblages, the members of each of which, while varying more or less in minor respects, had certain structural features in common, and these common morphological characters became the definition of the group thus formed. The smallest group thus constituted is a _Morphological Species_. A certain number of species having characters in common, by which they resemble one another and differ from all other species, constitutes a _Genus_; a group of genera, similarly associated, constitutes a _Family_; a group of families, an _Order_; a group of orders, a _Class_; a group of classes, a _Sub-kingdom_; while the latter, agreeing with one another only in the characters in which all animals agree, and in which they differ from all plants, make up the _Animal Kingdom_.

Linnæus, living at a time when neither comparative anatomy nor embryology can be said to have existed, based his classification of animals upon such broad resemblances of adult structure and habit as his remarkable sagacity and wide knowledge enabled him to detect. Cuvier and his school devoted themselves to the working out of adult structure, and the _Leçons d’Anatomie Comparée_ and the _Règne Animal_ are wonderful embodiments of the results of such investigations. But the Cuvierian system ignores development; and it was reserved for Von Baer to show the importance of developmental studies, and to inaugurate the marvelous series of researches which, in the course of the last fifty years, have made us acquainted with the manner of development of every important group of animals. The splendid researches of Cuvier gave birth to scientific palæontology, and demonstrated that, in some cases, at any rate, extinct forms of life present characters intermediate between those of groups which are at present widely different. The investigations of Agassiz upon fossil fishes tended in the same direction, and further showed that, in some cases, the older forms preserve, as permanent features, structural characters which are embryonic and transitory in their living congeners. Moreover, Darwin, Owen, and Wallace proved that, in any great area of geographical distribution, the later tertiary extinct forms are clearly related to those which now exist in the area. As Taxonomic investigations increased in accuracy and in extent, the careful examination of large suites of specimens revealed an unexpected amount of variability in species; and Darwin’s investigation of the phenomena presented by animals under domestication proved that forms, morphologically as distinct as admitted natural genera, could be produced by selective breeding from a common stock.

The only genus of animals of which we possess a satisfactory, though still not quite complete, ancestral history, is the genus Equus, the development of which in the course of the Tertiary epoch from an Anchitherioid ancestor, through the form of Hipparion, appears to admit of no doubt. And all the facts of geology and palæontology not only tend to show that the knowledge of ancestral development is likely long to remain fragmentary, but lead us to doubt whether even such fragments as may be vouchsafed to us by the extension of geological inquiry will ever be sufficiently old, in relation to the whole duration of life on the earth, to give us positive evidence of the nature of the earliest forms of animals.

In the case of an existing animal, it is possible to determine its adult structure and its development, and therefore to assign its place relatively to other animals, the structure and development of which are also known; and, in the case of an extinct animal, it is possible to ascertain certain facts of its structure, and sometimes certain facts of its development, which will justify a more or less positive assignment of its place relatively to existing animals. So far, Taxonomy is objective, capable of proof and disproof, and it should leave speculation aside, until speculation has converted itself into demonstration.

In the present rapidly shifting condition of our knowledge of the facts of animal structure and development, however, it is no easy matter to group these facts into general propositions which shall express neither more nor less than is contained in the facts; and no one can be more conscious of the manifold imperfections of the following attempt at such a classification than the author of it.

In certain of the lower animals, the substance of the body is not differentiated into histogenetic elements; that is, into cells[3] which, by their metamorphoses, give rise to tissues. In all other animals, on the other hand, the protoplasmic mass, which constitutes the primitive body, is converted into a multitude of cells, which become metamorphosed into the tissues of the body.

For the first of these divisions the old name of Protozoa may be retained; for the second, the title of Metazoa, recently proposed by Haeckel, may be conveniently employed.

The subjoined synopsis indicates the general relations of the different groups of the animal kingdom.

Those who are familiar with the existing condition of our knowledge of animal morphology will be aware that any such scheme must needs, at present, be tentative and subject to extensive revision, in correspondence with the advance of knowledge. Nor will they regard it as any objection to the scheme of classification proposed, that the divisions sketched out may be incapable of sharp definition--the constant tendency of modern investigations being to break through all boundaries of groups, and to fill up the gaps between them by the discovery of transitional forms. In the place of assemblages of distinctly definable groups, which it has hitherto been the object of the taxonomist to define and co-ordinate in precise logical categories, we are gradually learning to substitute series, in which all the modifications by which a fundamental form passes from lower to higher degrees of organic complication are summed up.

ANIMALIA

I.--PROTOZOA

i. MONERA
Protamœbidæ. Protomonadidæ. Myxastridæ, etc.

ii. ENDOPLASTICA
Amœbidæ. Flagellata. Gregarinidæ. Acinetida. Ciliata. Radiolaria

II.--METAZOA

A. Gastrææ

i. POLYSTOMATA
Porifera (or Spongida)

ii. MONOSTOMATA

1. ARCHÆOSTOMATA

α. _Scolecimorpha_ β. _Cœlenterata_
|
/-----------------|----------------\
Rotifera Nematoidea Hirudinea Hydrozoa
Turbellaria Oligochæta Actinozoa
Trematoda

2. DEUTEROSTOMATA

_a._ Schizocœla
|
/-------------------------|-------------------------\
_Annelida (Polychæta)_ _Gephyrea_ _Brachiopoda (?)_
_Arthropoda_ _Mollusca_ _Polyzoa (?)_

_b._ Enterocœla
|
/------------------------|------------------------\
_Enteropneusta_ _Chætognatha_ _Echinodermata_

_c._ Epicœla
|
/------------|----------\
_Tunicata_ _Vertebrata_

B. Agastrææ (provisional)
Acanthocephala. Cestoidea

THE FOUR CLASSES
--BARON CUVIER

If we consider only the organization and nature of animals, without regard to their size, utility, the greater or less knowledge we have of them, and other accessory circumstances, we shall find there are four principal forms, four general plans, if it may be so expressed, on which all animals seem to have been modeled, and whose ulterior divisions, whatever be the titles with which naturalists have decorated them, are merely slight modifications, founded on the development or addition of certain parts, which produce no essential change in the plan itself.

In the first of these forms, which is that of man and of the animals most nearly resembling him, the brain and principal trunk of the nervous system are inclosed in a bony envelope, formed by the cranium and vertebræ; to the sides of this intermedial column are attached the ribs and bones of the limbs, which form the framework of the body; the muscles generally cover the bones, whose motions they occasion, while the viscera are contained within the head and trunk. Animals of this form we shall denominate Animalia Vertebrata. They have, all, red blood, a muscular heart, a mouth furnished with two jaws situated either above or before each other, distinct organs of sight, hearing, smell, and taste placed in the cavities of the face, never more than four limbs, the sexes always separated, and a very similar distribution of the medullary masses and the principal branches of the nervous system.

By a closer examination of each of the parts of this great series of animals, we always discover some analogy, even in species the most remote from each other; and may trace the gradations of one same plan from man to the last of the fishes.

In the second form there is no skeleton; the muscles are merely attached to the skin, which constitutes a soft contractile envelope, in which, in many species, are formed stony plates, called shells, whose position and production are analogous to those of the mucous body. The nervous system is contained within this general envelope along with the viscera, and is composed of several scattered masses connected by nervous filaments; the chief of these masses is placed on the æsophagus and is called the brain. Of the four senses, the organs of two only are observable, those of taste and sight, the latter of which are even frequently wanting. One single family alone presents organs of hearing. There is always, however, a complete system of circulation, and particular organs for respiration. Those of digestion and secretion are nearly as complex as in the vertebrata. We will distinguish the animals of this second form by the appellation of Animalia Mollusca.

Although, as respects the external configuration of the parts, the general plan of their organization is not as uniform as that of the vertebrata, there is always an equal degree of resemblance between them in the structure and the functions.

The third form is that remarked in worms, insects, etc. Their nervous system consists of two long cords, running longitudinally through the abdomen, with which they communicate by filaments that encircle the æsophagus like a necklace. The covering or envelope of the body is divided by transverse folds into a certain number of rings whose teguments are sometimes soft, and sometimes hard; the muscles, however, being always situated internally. Articulated limbs are frequently attached to the trunk; but very often there are none. We will call these animals Animalia Articulata, or articulated animals, in which is observed the transition from the circulation in closed vessels to nutrition by imbibition, and the corresponding one of respiration in circumscribed organs, to that effected by tracheæ or air-vessels distributed throughout the body. In them the organs of taste and sight are the most distinct; one single family alone presenting that of hearing. Their jaws, when they have any, are always lateral.

The fourth form, which embraces all those animals known by the name of zoophytes, may also be properly denominated Animalia Radiata, or radiated animals. We have seen that the organs of sense and motion in all the preceding ones are symmetrically arranged on the two sides of an axis. There is a posterior and anterior dissimilar face. In this last division they are disposed by rays round a centre; and this is the case even when they consist of but two series, for then the two faces are similar. They approximate to the homogeneity of plants, having no very distinct nervous system or particular organs of sense; in some of them it is even difficult to discover a vestige of circulation; their respiratory organs are almost universally seated on the surface of the body, the intestine in the greater number is a mere sac without issue, and the lowest of the series are nothing but a sort of homogeneous pulp, endowed with motion and sensibility.

DEEP SEA FAUNA
--LORD KELVIN

Nearly all the animals at extreme depths--practically all the animals, for the small number of higher forms feed upon these--belong to one sub-kingdom, the Protozoa; whose distinctive character is that they have no special organs of nutrition, but absorb nourishment through the whole surface of their jelly-like bodies. Most of these animals secrete exquisitely formed skeletons, some of silica, some of carbonate of lime. There is no doubt that they extract both these substances from the sea-water; and it seems more than probable that the organic matter which forms their soft parts is derived from the same source. It is thus quite intelligible that a world of animals may live in these dark abysses, but it is a necessary condition that they must chiefly belong to a class capable of being supported by absorption through the surface of their bodies of matter in solution, developing but little heat, and incurring a very small amount of waste by any manifestation of vital activity. According to this view it seems probable that at all periods of the earth’s history, some form of the Protozoa--rhizopods, sponges, or both--predominated greatly over all other forms of animal life in the depths of the warmer regions of the sea. The rhizopods, like the corals of a shallower zone, form huge accumulations of carbonate of lime, and it is probably to their agency that we must refer most of those great bands of limestone which have resisted time and change, and come in here and there with their rich imbedded lettering to mark like milestones the progress of the passing ages.

We find the first and simplest of the invertebrate sub-kingdoms, the Protozoa, represented by three of its classes--the monera, the rhizopoda, and the sponges. The monera have been defined as a distinct class by Professor Ernst Haeckel, of a vast assemblage of almost formless beings apparently absolutely devoid of internal structure, and consisting simply of living and moving expansions of jelly-like protoplasm. The monera pass into the rhizopoda, which give a slight indication of advance in the definite form of the graceful, calcareous, shell-like structures which most of them secrete, and the two groups may be taken together.

The dredging at 2,435 fathoms at the mouth of the Bay of Biscay gave a very fair idea of the condition of the bottom of the sea over an enormous area, as we know from many observations which have now been made with the various sounding instruments contrived to bring up a sample of the bottom. Under the microscope the surface-layer was found to consist chiefly of entire shells of Globigerina bulloides, large and small, and fragments of such shells mixed with a quantity of amorphous calcareous matter in fine particles, a little fine sand, and many spicules, portions of spicules, and shells of Radiolaria, a few spicules of sponges, and a few frustules of diatoms.

In this dredging, as in most others in the bed of the Atlantic, there was evidence of a considerable quantity of soft gelatinous organic matter, enough to give a slight viscosity to the mud of the surface-layer. This gelatinous matter is capable of a certain amount of movement, and there can be no doubt that it manifests the phenomena of a very simple form of life.

To this organism, if a being can be so called which shows no trace of differentiation of organs, consisting apparently of an amorphous sheet of a protein compound, irritable to a low degree and capable of assimilating food, Professor Huxley has given the name of Bathybius haeckelii. The circumstance which gives its special interest to Bathybius is its enormous extent: whether it be continuous in one vast sheet, or broken up into circumscribed individual particles, it appears to extend over a large part of the bed of the ocean; and as no living thing, however slowly it may live, is ever perfectly at rest, but is continually acting and reacting with its surroundings, the bottom of the sea becomes like the surface of the sea and of the land--a theatre of change, performing its part in maintaining the “balance of organic nature.”

Living upon and among this Bathybius, we find a multitude of other protozoa--foraminifera and other rhizopods, radiolarians, and sponges; and we as yet know very little of the life-history of these groups.

Many foraminifera of different groups inhabit the deep water, lying upon or mixed in the upper layer of the globigerina ooze, or fixed to some foreign body, such as a sponge, coral, or stone; and all of these are remarkable for their large size.

The few hauls of the dredge which we have already had in deep water have been enough to teach us that our knowledge of sponges is in its infancy--that those which we have collected from shallow water along our shores, and even those few which have been brought up from deep water on fishing lines, and have surprised us by the beauty of their forms and the delicacy of their lustre, are the mere margin and remnant of a wonderfully diversified sponge-fauna which appears to extend in endless variety over the whole of the bottom of the sea.

The most remarkable new forms are referable to the group which seems to be in a sense special to deep water, the Hexactinellidæ. One of the most abundant and singular forms belonging to this order, Holtenia carpenteri, is an oval or sphere 90 to 100 mm. in height, with one large oscular opening at the top about 30 mm. in diameter, whence a simple cylindrical cavity cupped at the bottom passes down vertically into the substance of the sponge to the depth of 55 mm. The outer wall of the sponge consists of a complicated network of the cross-like heads of five-rayed spicules. One ray of each spicule dips directly into the body of the sponge, and the other four, which are at right angles to it, form a cross on the surface, giving it a beautiful stellate appearance. The silicious rays of one star curve toward and meet the rays of the neighboring stars, and run parallel with them. All the rays of all the spicules are thickly invested with consistent semi-transparent gelatinous matter, which binds their concurrent branches together by an elastic union, and fills up the angles of the meshes with softly curved viscous masses. This arrangement of the spicules, free and yet adhering together by long elastic connections, produces a strong, flexible, and very extensible tissue. The cylindrical oscular cavity within the sponge is lined with nearly the same kind of network.

When the sponge is living, the interstices of the silicious network are filled up both outside and in with a delicate fenestrated membrane formed of a glairy substance like white of egg, which is constantly moving, extending or contracting the fenestræ, and gliding over the surface of the spicules. This “sarcode,” which is the living flesh of the sponge, contains distributed through it an infinite number of very minute spicules, presenting the most singular and elegant forms very characteristic of each species of sponge. A constant current of water carried along by the action of cilia passes in by apertures in the outer wall, courses through the passages in the loose texture of the intermediate sponge-substance carrying organic matter in solution and particles of nourishment into all its interstices, and finally passes out by the large “osculum” at the top. Over the upper third of the sponge a multitude of radiating rigid silicious spicules form a kind of ornamental frill, and from the lower third a perfect maze of delicate glassy filaments, like fine white hair, spread out in all directions, penetrating the semi-fluid mud, and supporting the sponge in its precarious bed by increasing its surface indefinitely while adding but little to its weight.

This is only one of the ways by which sponges anchor themselves in the ooze of the deep sea. Hyalonema sends right down through the soft mud a coiled wisp of strong spicules, each as thick as a knitting needle, which open out into a brush as the bed gets firmer, and fix the sponge in its place somewhat on the principle of a screw pile. A very singular sponge from deep water off the Lofoten Islands spreads into a thin circular cake, and adds to its surface by sending out a flat border of silky spicules, like a fringe of white floss round a little yellow mat; and the lovely Euplectella, whose beauty is imbedded up to its fretted lid in the gray mud of the seas of the Philippines, is supported by a frill of spicules standing up round it like Queen Elizabeth’s ruff.

The sponges of the deep-water ooze are by no means confined to one group. The Hexactinellidæ are perhaps the most abundant, but corticate sponges even, closely allied to those which look so rigid when fixed to stones in shallow water, send out long anchoring spicules and balance themselves in the soft mud; and off the coast of Portugal Mr. Gwyn Jeffreys dredged in 1870 several small forms of the Halichondridæ, with long supporting fibrous beards.

From its appearance when brought up Holtenia evidently lives buried in the mud to its upper fringe of spicules. When freshly dredged, it is loaded with pale gray semi-fluid sarcode, full of Globigerinæ, Triloculinæ, and other rhizopods, and covered in our northern localities with the little ophiurid Amphiura abyssicola, Sars, and the exquisitely delicate transparent clam, Pecten viterus Chemnitz. Holtenia extends from the Butt of Lewis to Gibraltar, in from 500 to 1,000 fathoms.

In the Hexactinellidæ all the spicules, so far as we know, are formed on the hexradiate plan; that is to say, there is a primary axis, which may be long or short, and at one point four secondary rays cross this central shaft at right angles. In many of the Hexactinellidæ the spicules are all distinct, and combined, as in Holtenia, by a small quantity of nearly transparent sarcode; but in others, as in “Venus’s flower-basket,” and the nearly equally beautiful genera Iphiteon, Aphrocallistes, and Farrea, the spicules run together and make a continuous silicious network. When this is the case the sponge may be boiled in nitric acid, and all the organic matter and other impurities thus removed, when the skeleton comes out a lovely lacy structure of the clearest glass. The six-rayed form of the spicules gives the network which is the result of their fusion great flexibility of design, with a characteristic tendency, however, to square meshes.

Off the Butt of Lewis, in water of 450 to 500 fathoms, we met on two occasions with full-grown specimens of a species of the remarkable genus Hyalonema, with the coils in the larger examples upward of 40 centimetres in length.

A bundle of from 200 to 300 threads of transparent silica, glistening with a silky lustre, like the most brilliant spun-glass--each thread from 30 to 40 centimetres long, in the middle the thickness of a knitting-needle, and gradually tapering toward either end to a fine point; the whole bundle coiled like a strand of rope into a lengthened spiral, the threads of the middle and upper portions remaining compactly coiled by a permanent twist of the individual threads; the lower part of the coil, which, when the sponge is living, is imbedded in the mud, frayed out so that the glassy threads stand separate from one another, like the bristles of a glittering brush; the upper portion of the coil close and compact, imbedded perpendicularly in a conical or cylindrical sponge; and usually part of the upper portion of the silicious coil, and part of the sponge-substance, covered with a brownish leathery coating, whose surface is studded with the polypes of an alcyonarian zoophyte--such is the general effect of a complete specimen of Hyalonema.

The genus was first known in Europe by specimens brought from Japan by the celebrated naturalist and traveler, Von Siebold; and Japanese examples of Hyalonema sieboldi, Gray, may now be found more or less perfect in most of the European museums. When the first specimen of Hyalonema was brought home, the other vitreous sponges which approach it so closely in all essential points of structure were unknown.

In essential structure Hyalonema very closely resembles Holtenia, and the more characteristic forms of the Hexactinellidæ. On one of the Holteniæ from the Butt of Lewis, there was a little accumulation of greenish granular matter among the fibres. On placing this under the microscope it turned out to be a number of very young sponges, scarcely out of their germ state. They were all at first sight very much alike, minute pear-shaped bodies, with a long delicate pencil of silky spicules taking the place of the pear-stalk. On closer examination, however, these little germs proved to belong to different species, each showing unmistakably the characteristic forms of its special spicules. Most of them were the young of Tisiphonia, but among them were several Holteniæ, and one or two were at once referred to Hyalonema. In two or three hauls in the same locality we got them in every subsequent stage--beautiful little pear-shaped things, a centimetre long, with a single osculum at the top, and the wisp like a small brush. At this stage the Palythoa is usually absent, but when the body of the sponge has attained 15 mm. or so in length very generally a little pink tubercle may be detected at the point of junction between the sponge body and the coil, the germ of the first polype.

During Mr. Gwyn Jeffreys’s cruise in 1870, two specimens of a wonderful sponge belonging also to the Hexactinellidæ were dredged in 374 fathoms in rocky ground off Cape St. Vincent. The larger of these forms a complete vase of a very elegant form, nearly ninety centimetres in diameter at the top and about sixty in height. The sponge came up folded together, and had much the appearance of a piece of coarse, grayish-colored blanket.

Near the mouth of the Strait of Gibraltar a number of species were taken in considerable quantity, belonging to a group which were at first confused with the Hexactinellidæ, on account of their frequently forming a similar and equally beautiful continuous network of silica, so as to assume the same resemblance to delicate lace when boiled in nitric acid. The Corallio-spongiæ differ, however, from the Hexactinellidæ in one very fundamental character. While in the latter the spicule is hexradiate, in the former it consists of a shaft with three diverging rays at one end.

This group of sponges are as yet imperfectly known. They seem to pass into such forms as Geodia and Tethya; and the typical example with which we are most familiar is the genus Dactylocalyx, represented by the cup-shaped pumice-like masses which are thrown ashore from time to time on the West Indian Islands.

Twelve species of stony corals were dredged in 1869.

From their considerable size, the length and rigidity of their straggling rays, and their habit of clinging to fixed objects, the Echinodermata are not very readily taken by the dredge, but they fall an easy prey to the “hempen tangles.” It is possible that this circumstance may to a certain extent exaggerate their apparent abundance at great depths, but we have direct evidence in the actual numbers which are brought up that in some places they must be wonderfully numerous; and we frequently dredge sponges and corals actually covered with them in the attitudes in which they lived, nestling among their fibres and in the angles of their branches. I have counted seventy-three examples of Amphiura abyssicola, small and large, sticking to one Holtenia.

Both on account of their beauty and extreme rarity, and of the important part they have borne in the fauna of some of the past periods of the earth’s history, the first order of the Echinoderms, the Crinoidea, has always had a special interest to naturalists; and, on the watch as we were for missing links which might connect the present with the past, we eagerly welcomed any indication of their presence. Crinoids were very abundant in the seas of the Silurian period. But during the lapse of ages the whole order seems to have been worsted in the “struggle for life.” They become scarce in the newer Mesozoic beds, still scarcer in the Tertiaries, and up to within the last few years only two living stalked crinoids were known in the seas of the present period, and these appeared to be confined to deep water in the seas of the Antilles, whence fishermen from time to time bring up mutilated specimens on their lines. Their existence has been known for more than a century; but although many eyes have been watching for them, until very lately not more than twenty specimens had reached Europe, and of these only two showed all the joints and plates of the skeleton, and the soft parts were lost in all.

These two species belong to the genus Pentacrinus, which is well represented in the beds of the lias and oolite, and sparingly in the white chalk; and are named respectively Pentacrinus asteria, L., and P. mülleri, Oersted. The first of these has been known in Europe since the year 1755, when a specimen was brought to Paris from the island of Martinique, and described by Guettard in the Memoirs of the Royal Academy of Sciences. For the next hundred years an example turned up now and then from the Antilles.

Pentacrinus asteria may be taken as the type of its order; I will therefore describe it briefly. The animal consists of two well-marked portions, a stem and a head. The stem, which is often from 40 to 60 centimetres in length, consists of a series of flattened calcareous joints; it may be snapped over at the point of junction between any two of these joints, and by slipping the point of a penknife into the next suture a single joint may be removed entire. The joint has a hole in the centre, through which one might pass a fine needle. This hole forms part of a canal filled during life with a gelatinous nutrient matter which runs through the whole length of the stem, branches in a complicated way through the plates of the cup, and finally passes through the axis of each of the joints of the arms, and of the ultimate pinnules which fringe them. On the upper and lower surfaces of the stem-joint there is a very graceful and characteristic figure of five radiating oval leaf-like spaces, each space surrounded by a border of minute alternate ridges and grooves. The ridges of the upper surface of a joint fit into the grooves of the lower surface of the joint above it; so that, though from being made up of many joints the stem admits of a certain amount of motion, that motion is very limited.

As the border of each star-like figure exactly fits the border of the star above and below, the five leaflets within the border are likewise placed directly one above the other. Within these leaflets the limy matter which makes up the great bulk of the joint is more loosely arranged than it is outside, and five oval bands of strong fibres pass in the interspaces right through the joints, from joint to joint, from one end of the stem to the other. These fibrous bands give the column great strength. It is by no means easily broken even when dead and dry. They also, by their elasticity, admit a certain amount of passive motion. There are no muscles between the joints of the stem, so that the animal does not appear to be able to move its stalk at will. It is probably only gently waved by the tides and currents, and by the movements of its own arms.

In Pentacrinus asteria about every seventeenth joint of the lower mature part of the stem is a little deeper or thicker than the others, and bears a whorl of five long tendrils or cirri. These tendrils have no true muscles; they have, however, some power of contracting round resisting objects which they touch, and there are often star-fishes and other sea animals entangled among them.

Near the head the cirri become shorter and smaller, and their whorls closer. At the top of the stem five little calcareous lumps like buttons stand out from the projecting ridges, and upon these and upon the upper part of the stem the cup which holds the viscera of the animal is placed.

All the ordinary joints of the arms are provided with muscles producing various motions, and binding the joints firmly together. If one of the arms get entangled, or fall into the jaws or claws of an enemy, by a jerk the star-fish can at once get rid of the embarrassed arm; and as all this group have a wonderful power of reproducing lost parts, the arm is soon restored.

Unfortunately, most of the examples of Pentacrinus asteria hitherto procured have had the soft parts destroyed and the disk more or less injured. One specimen, however, in my possession is quite perfect. The body is covered above by a membrane closely tessellated with irregularly formed flat plates. The mouth is a rounded opening of considerable size in the centre of the disk, and opens into a stomach passing into a short curved intestine which ends in a long excretory tube--the so-called “proboscis” of the fossil crinoids--which rises from the surface of the disk near the mouth. From the mouth five deep grooves, bordered on either side by small square plates, run out to the edge of the disk, and are continuous with the grooves on the upper surface of the arms and pinnules, while in the angles between them five thickened masses of the mailing of the disk surround the mouth like valves. These were at first supposed to answer the purpose of teeth. The crinoids, however, are not predatory animals. Their nutrition is effected in a very gentle manner. The grooves of the pinnules and arms are richly ciliated. The crinoid expands its arms like the petals of a full-blown flower, and a current of sea-water bearing organic matter in solution and suspension is carried by the cilia along the brachial and radial grooves to the mouth. In the stomach and intestine the water is exhausted of assimilable matter, and the length and direction of the excretory proboscis prevent the exhausted water from returning at once into the ciliated passages.

Two other fixed crinoids were dredged from the _Porcupine_, and these must be referred to the Apiocrinidæ, which differ from all other sections of the order in the structure of the upper part of the stem.