firmed; and we are now so familiar with the outlines of the history of the fresh-water polype, and its marvellous reproductive powers, that we can scarcely appreciate the vividness of the sensation felt when it was all novel and strange when the leading men of our learned societies were daily experimenting on these poor worms, and transmitting them to one another from distant countries, by careful posts, and as most precious gifts; and when even ambassadors interested themselves in sending early intelligence of the engrossing theme to their respective courts."*

Let us try to see what Trembley saw. Put the phial in a window, and allow it to remain untouched a while. The balls of jelly have all attached themselves, some to the glass sides, some to the plant, but they are balls no longer. Each is a thread of some half-inch in length, and about as thick as small twine, adhering by one extremity; while from the other radiate, like a star, six slender threads, which are waved irregularly through the water, thrown into spiral coils or various contortions, elongated, contracted, elongated again, slowly or suddenly, and in different degrees. Two or three minute water-insects are swimming giddily about; one of them, as he shoots unconsciously by, just touches one of these slender threads. In an instant the playful course is arrested; the little thing strives to pursue his way, drags the flexible cord that holds him hither and thither; redoubles his efforts, pulls away and stretches it till we think it must break and free him. No! like a skilful angler, the Jelly is but wearying his victim suddenly the thread is thrown into corkscrew coils,

* Johnston, Brit. Zooph. 126,

and the helpless insect is dragged in; another thread is brought to bear upon it, and another. Poor thing! "actum de eo est," it is all up with him! He is dragged helplessly to the base of the radiating threads, and there, in the midst of their circle, an aperture is gaping, which stretches wider and wider, while the prey is slowly sucked in, until it is quite engulphed within the gelatinous body.

But, for some time before this, the prey had become quite motionless; its struggles, though violent at first, had soon entirely ceased, and it was evident that a fatal effect had been produced by the mere contact of those slender threads.

What is the nature of this subtle venom that resides in a creature apparently so low in the scale of being, so simple in structure, and almost homogeneous in substance? Worms, and the larvæ of insects, that may be wounded, and even chopped into pieces, and yet survive for hours, die suddenly from a touch of these gelatinous threads! "I have sometimes," says Baker, "forced a worm from a polype the instant it has been seized, at the expense of breaking off the polype's arms, and have always observed it to die very soon afterwards, without one single instance of recovery. On the other hand, the tiny water-fleas, and other minute Crustacea, frequently escape with impunity even from the very mouth of the polype; for they are enclosed in a horny shell, which evidently protects their vital parts from the morbific touch.

The microscope throws light on the question, and reveals a most elaborate system of offensive weapons with which these soft and sluggish creatures are provided.

* History of the Polype, 33.

According to Corda, each tentacle forms a slender membranaceous tube, filled with an albuminous substance nearly fluid, mingled with some oily particles. This substance, at certain definite points, swells out into tubercles or dense warts, which run round the tentacle in a spiral line. Each wart is furnished with several spinebearing vesicles, which are organs of touch, and with an organ of highly curious structure, which is the weapon of offence.

The organ of touch consists of a fine sac, enclosing another with thicker walls, within which there is a small cavity. From the upper extremity, where the inner and the outer sacs are in contact, there projects a long cilium, or fine pointed bristle, which is not retractile, and appears to be immoveable.

The weapon of offence is placed in the midst of these spines, in the centre of each wart. It consists of an oval transparent sac, imbedded in the substance of the wart, with its perforated extremity exactly at the surface. At the bottom of the interior of the sac there is a body, in shape resembling a saucer, in the centre of which stands a small oval, solid body, bearing on its summit a calcareous dart, pointed at its extremity, and bifid, or sagittate, at its base. This dart can be projected at the will of the animal, and again withdrawn into the sac. When the prehensile instinct is exerted, the darts are thrust out with force, and, entering the tissues of the prey, retain it : while at the same time, in all probability, a subtle but potent poison is injected, the effects of which we have already alluded to.

But this is a modern discovery. The circumstance in

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