the economy of these animals which appeared so anomalous, was the mode in which they were both naturally and artificially multiplied. They were manifestly animals, yet it was found that they could be propagated by slips or cuttings, like plants! In the warm weather of summer each polype is observed to shoot forth, from various parts of its body, little warts, or knobs, which increase rapidly, until in a few days they assume the form of the parent animal, each one being furnished with a circle of tentacles, though still attached at its lower end. The young one, which up to this period had received its nutriment from the parent's stomach, from which a channel had communicated with its own, now catches prey with its own tentacles, the duct closes, the connexion of the base with the mother becomes more slender, and at length the little animal falls off, and commences independent life. Such is the ordinary mode of increase-generation by gemmation.

In autumn, the Hydra propagates by means of eggs, which are deposited around the parent; the basal portion of her body being spread over them, and becoming a horny protecting skin. She immediately dies, and the eggs are hatched in the ensuing spring.*

But these strange animals may be artificially increased at pleasure, and that by means which, to higher animals, would inevitably destroy, instead of multiplying life. If the head of a polype, with all its tentacles, be cut off from the trunk with scissors, it will presently develop a new trunk and base, while the headless trunk begins to shoot out new tentacles; and thus, in a little time, two perfect

* Laurent, L'Institut, No. 465.

animals are formed. If one of these be cut into three, four, or half-a-dozen pieces, each piece supplies the wanting parts, and so many animals are made, all as perfect and active, and endowed with the same functions, as the first. Nor does it signify in what direction the mutilation is made; a longitudinal, a diagonal, or a transverse division is equally successful; nay, even a small portion of the skin soon grows into a polype.

It was from this power of perpetual reproduction, that this singular animal received the name of Hydra, by which it is known among naturalists; as if it realised the ancient monster of fabulous story, whose heads sprouted anew as fast as they were cut off by Hercules.

Most curious monstrosities were produced by the experiments of philosophers on these animals, especially by partial separations. If a polype be slit from the summit to the middle, one will be formed having two heads, each of which will capture and swallow food. If these again be slit half-a-dozen times, as many heads will be formed surmounting the same body. If now all these be cut off, as many new ones will spring up in their place, while each of the severed heads becomes a new polype, capable of being, in its turn, varied and multiplied ad infinitum ;— so that in every respect our little reality exceeds its fabulous namesake.

The polypes may be grafted together. If cut-off pieces be placed in contact, and pushed together with a gentle force, they will unite and form a single one. The head of one may be thus planted on the trunk of another.

Another method of uniting them, perhaps still more wonderful, is by introducing one within the other; the

operator forced the body of the one into the mouth of the other, pushing it down so that the heads were brought together. After forcibly keeping it for some time in this. state, the two individuals at length united, and a polype was formed, distinguishable only by having twice the usual number of tentacles.

There is one species which can actually be turned inside out like a glove, and yet perform all the functions of life as before, though that which was the coat of the stomach is now the skin of the body, and vice versâ. If it should chance that a polype so turned had young in the act of budding, these are, of course, now within the stomach. If they have arrived at a certain degree of maturity, they extend themselves towards the mouth of the parent, that they may thus escape when separated. But those which are less advanced turn themselves spontaneously inside out, and thus place themselves again on the exterior of the parent.

A multitude of other variations, combinations, and monstrosities, have been, as it were, created by the ingenuity of philosophers; but these are sufficient to give a notion of the extraordinary nature of these animals, and to account for the wonder with which they were regarded.

The Hydra was, until lately, considered as an animal of very simple structure, being composed of mere granules of jelly, set in a glairy, enveloping fluid. But the further we push our researches, the more are we disposed to hesitate in pronouncing on the comparative simplicity or complexity of any organism. We have already seen the elaborate array of weapons in the tentacles. M.

Gervais has shewn that the component granules of the body are of diverse forms, and, in all probability, sustain different relations to the general economy. The whole body consists of a sac, with thin dilatable walls, enclosing a capacious cavity, which forms the stomach: the granules which border this cavity are conical papillæ projecting into the stomach, and are supposed to have a digestive function; the exterior series are lengthened, and constitute an integument, while some of the intermediate ones are arranged in bands, which are, with little doubt, presumed to be muscular. The muscular bands in the ten

tacles are still more distinct, running in four series, which pass diagonally to and fro from side to side, forming lozenge-shaped spaces by mutual intersection.

CHAPTER VI.

POLYPIFERA (Polypes).

Continued.

LET us suppose that the buds continually put forth from the sides of the Hydra, instead of falling off to commence a new and isolated existence, remained permanently attached to the parent stock, giving forth in their turn buds, becoming permanent branches. We should then have the essential form of a Compound Polype; such, for example, as that of the great marine family, Sertulariada. Here we find the germ first developing a single Hydra-like polype, consisting of a slender stem or body of granular flesh, enclosing a stomachal cavity, the orifice of which is surrounded by a circle of sensitive tentacles. Soon, however, a lateral bud projects, which shoots upward and develops a similar head of tentacles, while, from the side of this, another shoot still carries up the rising stem, which assumes a plant-like condition of branching stalks, with many lateral tentacled buds. It is true that in these marine species we commonly find an additional structure, of which no trace appears in the fresh-water Hydra. The whole compound animal is enclosed in a tube of transparent substance, somewhat flexible though firm, resem