THE COMATULIDE.

This family, the species of which are called Hair-Stars or Feather-Stars, includes a con

siderable number of animals, which bear

a great resemblance, both in form and structure, to the Encrinidæ. They are, however, only furnished with a stalk during their young state, and on arriving at maturity they quit their attachment, and crawl about freely at the bottom of the water, in the same manner as other starfishes. The body is flattened and covered with separate calcareous plates; the lower, or ventral surface, bears the mouth and anus; and the ten slender rays are often branched to such an extent as to appear very numerous. These are furnished throughout their length with slender, jointed cirri, similar to those of the Encrinidæ, by the assistance of which and the short ambulacra, the Hair-Stars are enabled to grasp any object firmly, and creep about on submarine plants with great ease.

In their young state, the Comatulæ greatly resemble the animals of the preceding family, being supported on a long flexible stalk, formed of calcareous cylinders. So close is this resemblance, that when first discovered the young of the Comatula was described as a Pentacrinus. These animals are tolerably numerous in the seas of the present day, where they constitute, in fact, the principal In the representatives of their order. earliest ages of the world, their place was taken by the fixed Encrinidæ; and the free Comatulæ do not make their appearance in any formation earlier than the Jurassic strata.

Class II. SIPHONOPHORA.

The Siphonophora form a group of animals of which we have still much to learn before their true nature and relations can be ascertained. They are divided into two orders-the Physograda and Chondrograda.

ORDER 1. PHYSOGRADA.

The characteristic of the animals forming this order is, that they are furnished with a vesicular organ containing air, which serves as a float to buoy them up in the water. The best known of this species is the Physalia Atlantica, which has received from sailors the name of the Portuguese Man-of-War. It swims in great crowds at the surface of the water, and possesses a very strong urticating or stinging power.

ORDER 2. CHONDROGRADA.

These animals are called Chondrograda from the circumstance that the circular or oval disc, of which their body is composed, is supported upon a somewhat cartilaginous plate, which sometimes even contains a calcareous deposit; the lower surface of this disc is furnished with cirri, some of which are tubular. Many of these creatures are exceedingly beautiful, blue being their prevailing color. In the genus Porpita, one species of which is found in the Mediterranean, the disc is surrounded by a beautiful fringe of tentacles; but the most remarkable structure is presented by the Velella, in which an oblique upright crest is developed upon the upper surface of the disc, serving as a sort of sail to waft the little mariner from place to place. One species of this genus is found on the coasts of Ireland.

Class III. CTENOPHORA,

We now come to a class of animals, the real nature of which is still to be made out. They

are gelatinous, transparent creatures, generally of an oval form, enabled to swim freely by the action of variously-arranged rows of cilia.

The Beroida, which form the first family, may almost be said to possess no true stomach, the body being so formed as to inclose a great cavity, of which the hinder portion serves as a digestive organ. When the animals have much food in this cavity, they constrict the middle of the body so as to prevent any of it from escaping. The body is oval or roundish, with eight rows of cilia running from one end to the other. The mouth is large, and opens and shuts with facility; it is generally held open when the creature is in motion. The tentacles are wanting in this family. The species are gelatinous, and at night shine like lamps suspended in the water

THE CYDIPPE, FORMERLY CALLED THE BEROE PILEUS.

The Callianirida are distinguished from the Beroide by the small size of the stomach and mouth, and by the possession of filamentous tentacles. The Cydippe, formerly called Beroe Pileus, is now referred to this family, it has a globular body, with two long ciliated appendages. But

VENUS' GIRDLE.

the most singular of these animals is the VENUS' GIRDLE, Cestum Veneris, which inhabits the Mediterranean, and which at first sight would be taken for any thing rather than a near relation of the little globular Cydippe. In this curious creature the sides of the body are produced into a long ribbon, which sometimes attains the length of four or five feet; the mouth and digestive organs being, however, confined to their original position in the middle of the body. This animal is one of the most beautiful inhabitants of the ocean. When in motion, its waving cilia, which are placed along

the margins of the body, glitter with all the tints of the rainbow; at night it appears like a long waving flame in the water.

Class IV. DISCOPHORA.

This term is from the Greek diskos, a disc, and phero, to bear, and alludes to the general form of the animals belonging to this class. They bear the popular names of JELLY-FISHES and SEA-BLUBBERS, from their gelatinous nature, and SEA-NETTLES, from the stinging sensation they have the power of producing when touched; the term Acalephe, which has been generally applied to them, has this signification. They are exclusively natives of the ocean, which teems with them, from the intertropics to the polar circle. Among the strange and beautiful creatures which tenant the thronged and populous waters of the sea, they exhibit sometimes the most fantastic, sometimes the most elegant figures, adorned with colors of surpassing richness; nor is their variation in size less striking than that of their forms. Some are so minute as to require the aid of a microscope, in their examination; others form large masses, which, as they float on the waves, cannot but attract attention. Many shine with phosphorescent brilliance; as the vessel plows the briny water, or the oars of the boat throw up the spray, when darkness covers the face of the deep, they glitter like a shower of stars, and falling again, are lost in a sea of effulgence. Some appear in the depths like balls of glowing metal; some move with an undulating course, appearing as they pass like a ribbon of flame; others like diamonds gem the rocks or the fronds of seaweed; some float in shoals, displaying the lovely tints of the rainbow; while others, like orbs of silver, glitter as they float on the rolling current. They appear to be of a homogeneous and gelatinous consistence, but in reality are composed of filmy tissues, disposed in a cellular manner, and inclosing an abundance of sea-water, which, when they are left dead on the beach, soon dries up, leaving only a little scum or gummy web behind.

case.

THE PELAGIA LABICHE.

"In walking along the sea-beach," says Dallas, "as the tide is falling, the attention of the wanderer is often attracted by the number of singular gelatinous masses left on the sands. At first sight it would never be suspected that these are really living animals endowed with a structure of considerable complexity; but a very little examination will soon show the observer that this is the If one of these lumps of jelly be put into a clear pool or basin of sea-water, parts, before confounded in a shapeless mass, immediately unfold themselves; a circular, umbrella-like disc, surrounded by numerous short filamentous tentacles, appears to support the creature at the surface of the water; and from the center of this, depend four long arms with membraneous fringed margins. This is the Medusa aurita, one of the commonest species, and must have been often observed by those who frequent the sea-shore. In the water the creature swims along most gracefully by the contraction and dilatation of its transparent disc."

THE MEDUSA AURITA.

All the animals of this class present a structure very similar to this. They all possess a disc of greater or less convexity, which is employed, in the manner already described, for the purposes of locomotion; and in most of them the margin of this disc is furnished with tentacles or cirri. The disc, or umbrella, consists of two membranes, of which the lower is called the sub-umbrella. In the center of this the mouth is situated, sometimes at the extremity of a peduncle of variable length, which contains the stomach, and in some cases also the ovaries. The mouth is most frequently furnished with tentacles. Some genera, although provided with a large peduncle or with tentacles, are said to have

no mouth, the nourishment being absorbed through a number of small pores scattered upon these organs, and communicating by minute tubes with the stomach, which, as usual, is situated in the peduncle.

THE FAVONIA OCTONEMA.

It would be in vain to attempt to describe the various forms of these creatures. We give a few engravings, representing some of the most characteristic; as the Favonia octonema, with a nearly hemispherical body, showing a long proboscis, at the root of which are eight branchiferous appendages-inhabiting the South Seas: the Pelagia Labiche, with four foliaceous. arms, and long filaments depending from the rim of the umbrella-also found in the South Seas; and the Cuvieria carisochroma, which is without a central peduncle, yet has numerous long appendages hanging from its border.

The stinging power, which is common to several groups of radiate animals, is possessed by many Medusa in the greatest perfection. Of the Cyanea capillata-a species common on

the British coast-Professor Forbes speaks as follows: "This inhabitant of our seas is a most

formidable creature and the terror of tender-skinned bathers. With its broad, tawny, festooned and scalloped disc, often a full foot, or even more across, it flaps its way through the yielding waters, and drags after it a long train of ribbon-like arms and seemingly interminable tails, marking its course when the body is far away from us. Once tangled in its trailing 'hair' the unfortunate who has recklessly ventured across the graceful monster's path too soon writhes in prickly torture. Every struggle but binds the poisonous threads more firmly round his body, and then there is no escape; for when the winder of the fatal net finds his course impeded by the terrified human wrestling in his coils, he, seeking no combat with the mightier biped, casts loose his envenomed arms and swims away. The amputated weapons, severed from their parent body, vent vengeance on the cause of their destruction, and sting as fiercely as if their original proprietor itself gave the word of attack." This is a large species; most of the smaller ones appear to possess no urticating power, at least none capable of making an impression upon the human skin.

THE CUVIERIA CARISOCHROMA.

The reproduction of the Medusa has been a subject of the most elaborate investigation. These animals are all unisexual, and propagate by eggs, which the female produces in glandular organs, sometimes arranged in bands or patches on the surface of the sub-umbrella, and sometimes in cavities at the base of the peduncle. But these ova, when excluded, produce creatures very different from the parents, and it is not till the second generation that the original Medusa is reproduced. This has led to the following theory, put forth by Steenstrup: "The fundamental idea expressed by the words 'Alternation of Generations,' is the remarkable phenomenon of an animal producing an offspring which at no time resembles its parent, but which, on the other hand, itself brings forth a progeny which returns in its form and nature to the parent animal, so that the maternal animal does not meet with its resemblance in its own brood, but in its descendants of the second, third, or fourth degree of generation. And this always takes place in the different animals which exhibit the phenomena in a determinate generation, or with the intervention of a determinate number of generations. This remarkable precedence of one or more generations, whose function it is, as it were, to prepare the way for the later succeeding generation of animals destined to attain a higher degree of perfection, and which are developed into the form of the mother, and propagate the species by means of ova, can, I believe, be demonstrated in not a few instances in the animal kingdom."

Forbes admits the general correctness of this theory, but considers that in regard to the Medusa it has many exceptions, and in illustration of this view states that at least four British speVOL. II.-80

cies of Medusa, two of Lizzia and two of Sarsia, have the power of producing young animals by direct gemmation, and their development from a zoophytic form has not yet been observed. In Lizzia and Sarsia gemmifera the buds are produced from the stomachal peduncles; but in the other species of Sarsia, S. prolifera, they originate from the bulbs at the base of the tentacles, where they may be seen attached in all stages of development. "What strange and wondrous changes!" says he, after detailing his observations upon the last-mentioned minute Medusa. "Fancy an elephant with a number of little elephants sprouting from his shoulders and thighs, bunches of tusked monsters hanging, epaulette-fashion, from his flanks, in every stage of advancement! Here a young pachyderm, almost amorphous; there one more advanced, but all ears and eyes; on the right shoulder a youthful Chuny, with head, trunk, toes, no legs, and a shapeless body; on the left, an infant better grown, and struggling to get away, but his tail not sufficiently organized as yet to permit of liberty and free action! The comparison seems grotesque. and absurd; but it really expresses what we have been describing as actually occurring among our naked-eyed Medusa. It is true that the latter are minute; but wonders are not less wonderful for being packed into small compass."

Wonderfully beautiful are many of these creatures in form and color, but, as we have before stated, the amount of solid matter contained in their tissues is incredibly small. The greater part of their substance appears to consist of a fluid, differing little, if at all, from the sea-water in which the animal swims, and when this is drained away, so extreme is the tenuity of the membranes which contained it, that the dried residue of a jelly-fish weighing two pounds, which was examined by Professor Owen, weighed only thirty grains. Yet these creatures are capable of executing movements with considerable vivacity—their disc contracts and dilates alternately by the action of a band of what must be regarded as a muscular tissue-their tentacles are capable of seizing upon and destroying, by a subtle venom, animals of far more complicated structure than themselves, and their delicate stomachs have the power of speedily digesting the victim. In fact, in spite of the extreme delicacy of their texture, the Medusæ are among the most voracious inhabitants of the ocean. Small fishes and crustacea, and all the infinite multitude of minute marine creatures, are seized and paralyzed by their deadly arms; and as the mouth and stomach are capable of almost indefinite dilation, the size of their prey often appears exceedingly disproportionate. Of the voracity of one of the most delicate and beautiful species of the small Medusæ inhabiting the British shores, the Sarsia tubulosa, a little creature of the size and shape of a very small child's thimble, Professor Forbes speaks as follows: "Being kept in a jar of salt water with small crustacea, they devoured these animals, so much more highly organized than themselves, voraciously, apparently enjoying the destruction of the unfortunate members of the upper classes with a truly democratic relish. One of them even attacked and commenced the swallowing of a Lizzia octopunctata, quite as good a Medusa as itself. An animal which can pout out its mouth twice the length of its body, and stretch its stomach to corresponding dimensions, must, indeed, be 'a triton among the minnows,' and a very terrific one too."

Professor Forbes separates the Medusa into two great divisions, which we shall adopt as orders. In the first of these the ocelli, or eye-like spots, surrounding the margin of the disc, are protected by more or less complicated membraneous hoods or lobed coverings, while in the second these organs are naked. Hence the former are called Steganophthalmata, Covered-eyed, the latter Gymnophthalmata, or Naked-eyed. In the latter the ocelli, when present, are always placed on the bulbs at the base of the tentacles, and frequently also on the interstices between them. In the first order, on the contrary, they are always placed between the marginal tentacles.

ORDER 1. STEGANOPHTHALMATA.

The Meduse of this order often attain a gigantic stature: the Rhizostoma Cuvieri, a British species, measures two feet, or even more, in diameter, while some of the inhabitants of tropical seas are said to attain a still larger size. In calm weather they often swim close to the surface of the sea, in such multitudes as to impede the motion of a boat through the water. Such a