We may now be permitted to make a few reflections on this singular animal. On considering the various properties that have been already described, many particulars will be found in them that are very analogous to others that are continually carrying on around us; we perceive that there is a successive unfolding of new parts. In every organized frame there is a continual effort to extend its sphere of action, and enlarge the operation of that portion of life which is communicated to it. This gradual evolution requires a secret and curious mechanism, to regulate and modify by re-action the continued conatus of the forming principle within it. The polype is an organized whole, of which each part, each molecule, each atom, tends to produce another; it is, if we may so speak, one entire ovary, a compound of germ, or seed. In cutting a polype to pieces, the nourishing juices, which would have been employed in supporting the whole, are made to act upon each portion.
When a polype is divided longitudinally, it forms two half tubes; the opposite edges of these approach, and in a very short time form a perfect tube. The sides are made to touch each other by certain motions and contractions of the piece; but as soon as the edges come in contact, a slight adhesion takes place, the corresponding vessels unite, and new ones are unfolded, as in a vegetable graft; by these means the points of connection and cohesion are multiplied, the motion of the fluids is re-established, and with them the vital œconomy. This is performed with more rapidity than in vegetables, because the polype is nearly gelatinous, and its parts are extremely ductile; this ductility is supported and preserved by the element which it inhabits. The same reasoning applies equally to explain the formation of so many heads to a polype, as constitute it a real hydra.
A new polype is formed out of small portions or fragments, in a very different manner, the operations in nature being always varied, according as the circumstances differ; each fragment is puffed up, the skin separated, and an empty space is formed within it; this part is to become the stomach of the rising polype, which soon sends forth arms, and is formed to the perfection proper to its kind. We learn from this instance that the skin of the polype is not so simple as was at first imagined; for we find it dividing itself into two membranes, and forming thereby a cavity fit to perform all the functions of a stomach; but why these membranes are separated in the small portions, and not in the larger, we cannot tell; but though we are ignorant of this, and many more circumstances relative to the re-production of these little animals, yet the foregoing facts enable us to understand better the nature of the existence of these polypes which have been turned inside out.
For as that part which formed the interior skin of the stomach in the little fragments before-mentioned, became the exterior part of the animal, the inside of the polype is consequently so similar to the exterior skin, that one may be substituted for the other, without injuring the vital functions; from hence we might, in some measure, have inferred the possibility of the polypes living, after they have been turned inside out, independent of the fact itself.
The viscera of the animal are situated in the thickness of the skin, and absorbing pores are placed both on the inside and outside, so that the animal can live whether the skin be turned one way or the other. The Author of nature did not create the polype to be turned as we turn a glove; but he formed an animal whose viscera were lodged in the thickness of the skin, and with powers to resist the various accidents to which it was unavoidably exposed by the nature of its life; and the organization necessary for this purpose was so constructed, that the skin might be turned without destroying life.
Every portion of a divided polype has, like the vegetable bud, all the viscera necessary to its existence; it can, therefore, live by itself, and push forth a head and tail, when placed end to end against another piece. The vegetation consists in uniting the portions, the vessels of each part increase in length, and a communication is soon formed between them, which unites the whole. The ease with which the parts unite, is as has been observed before, probably owing to their gelatinous nature; for we find many similar instances in tender substances. The solid parts of the embryo, as the fingers, unite in the womb; tender fruit and leaves may be also thus united.
A portion of these creatures is capable of devouring its prey almost as soon as it is divided from the rest. In the structure of those animals which are most familiar to us, a particular place is appropriated for the developement and passage of the embryo. But on the body of an animal, which, like a tree, is covered with prolific gems, it is not surprizing that the young ones should proceed from its sides, like branches from a tree. The mother and her young ones form but one whole; she nourishes them, and they contribute to her existence, as a tree supports, and is reciprocally supported by its branches and leaves.
OF THE HYDRA PALLENS.
The hydra pallens has been fully described only by M. Rösel;[113] it is very seldom to be met with, is of a pale yellow colour, and grows smaller gradually from the bottom, the tail is somewhat round or knobbed, the arms are about the length of the body, of a white colour, and generally seven in number, apparently composed of a chain of globules; it brings forth the young from all parts of its body. Linnæus defines it as, hydra pallens tentaculis subsenis mediocribus;[114] Pallas as, hydra attenuata corpore flavescente, sursum attenuato.[115]
[113] Insecten Belustigung, 3. Theil. pag. 465. Tab. LXXVI. LXXVII.