It is to some interesting portions of structure presented by the animals of these four great groups or classes that we shall chiefly attend. They constitute, according to the arrangement of modern naturalists, a sub-kingdom of the animal world, termed by Cuvier the vertebrate; and in like manner the classes of animals still lower in the scale are grouped into great subkingdoms; but the grounds of distinction between those classes are, in many instances, less rigidly marked out. Their characters are, in fact, more indeterminate.

The sub-kingdom succeeding the vertebrate, (that is, possessing a true brain and spine,) comprehends numerous classes in which nerves exist, but in which there is no true brain, (in some, perhaps, rudiments of it,) but no spinal cord or spinal column. These have been commonly called molluscous animals, including the cuttlefishes, the nautilus, the little northern clio the food of the whale; slugs and snails, or univalve-shelled slugs, terrestrial and aquatic, as the whelk, the murex, etc.; bivalve-shells or shellfish, as oysters, mussels, etc.; certain mollusks invested in a sort of cartilaginous tunic, found in the warmer seas; including the pyrosoma, celebrated for its phosphorescence,

and others; to the barnacles, all arranged in their respective classes.

The next sub-kingdom, containing the crustaceous animals, as crabs and lobsters; the spiders and scorpions; true insects; the myriapods, millipedes, etc.; and the ringed worms, as the earthworm, leech, etc. In this subkingdom there are nerves uniting together a series of nervous knots termed ganglia, distributed with systematic regularity. The body consists of a succession of rings or annulations, formed by the integument, which may be soft, as in the leech, or rigid and calcareous, as in the lobster.

The next sub-kingdom comprehends the sea-urchins and star-fishes; the tripangs, so much esteemed in China as delicacies of the table; certain parasitic worms, as the guineaworm, and the various species of ascaris; the wheel animalcules, and a group of curious zoophites, called moss corals, of which the flustra, common along our coasts, is an example. In this sub-kingdom the nerves, where traceable, appear in the form of minute threads diversely arranged.

The last sub-kingdom embraces the seaanemones, the ordinary zoophites and coral

forming polypes; the jelly-fish and sea-nettles; the polygastric animalcules; the sponges, and the tapeworms and hydatids. In this subkingdom, the body of the various animals it embraces consists of an apparently homogeneous gelatine, often investing a framework of solid material, often inclosed in tubes sometimes simple, sometimes beautifully frondescent; in other cases, it has no support: in some instances, the animals move freely at pleasure, in others they are fixed and have a plant-like existence. Some species are simple; others form, by a vital union, a compound being, consisting of myriads of polypes, each distinct, yet all united into a whole by means of filaments, or a common gelatinous support. In some groups, we behold a number of bodies of a definite figure linked in floating chains together, but by a tie so slight that it is not easy to understand the nature of the union between them, or determine precisely whether this union be necessary for their individual vitality or not. In some groups a digestive laboratory is evident; in others mere canals traverse the gelatine through which the absorbed fluids circulate, till they are carried to a central cavity, and this is at once the apparatus of

nutrition and respiration. Many of these beings are beautifully phosphorescent; some exude an acrid humour, which gives pain to the hand incautiously applied to them. There is no distinction of sexes, and reproduction is either by the simple division of the original body into several parts, which ultimately assume the characteristic form, or by granules, which become gradually developed and detached from the parent; or by gemmules or buds, which, when thrown off, in due time display their specific characteristics.

But we must not extend these general observations by entering into particulars; suffice it, in the present place, to have alluded to them. Yet we have said enough to show the amazing extent of the animal kingdom, and the bewildering multiplicity, variety, and strangeness of the forms with which life is invested. Among the lowest groups of the animal creation, in particular, we are perpetually startled and ready to ask, Can these things truly belong to the animal kingdom? Can this plant-like assemblage of delicate stems and branches, studded with miniature cups and vases, or belllike flowerets, and rooted upon a shell or pebble cast by the waves on the sea-beach-can this

be an animal? No, not itself an animal, but the tenement of myriads of polypes, united together by a gelatinous thread running through each tubular ramification; and as the shell is secreted and deposited by the snail, so is this rooted abode secreted by the living zoophite. "I can believe," some one may say, "that the beautiful sea-anemones which bestud the tide-covered rocks along our coast are animals, for I have watched the creatures expand their green and azure arms or feelers, encircle them round small crabs, and drag the victim to their mouth; but will you tell me that the sponge on my dressing-table is an animal ?" It is not an animal, but it is the support of a gelatinous living film, which pervaded every pore of the elastic mass, and of which it may be considered as the rude skeleton. By that living gelatine, once a free swimming gemmule, the substance we call sponge, is secreted; that gemmule thrown out from one of the larger pores or canals of the parent sponge, swam about by means of little fibrils, till it found a suitable place on which to fix itself; there it adhered, and there, losing its pristine form, it became what it was when the diver or the dredger tore it from the rock, washed away the decomposing