Page:Scientific Memoirs, Vol. 1 (1837).djvu/255

Rh under the influence of light; wherefore, though sometimes fettered to the earth, it is by no means fixed or rooted in it, to which circumstance it owes its faculty of locomotion.

A further consequence which flows from the above consideration is, that the animal cannot, like the plant, draw its nourishing juices from the soil, because its whole organism has a tendency to inward unity; its very root-organs are turned inwards and formed into intestines; from which we are able to show most evidently the origin of the excretory canal and of the absorbent and circulating vessels. Let us suppose for instance a plant A, living with the atmospheric part + aboveground, and with its terrestrial part — underground; let us now detach it from the ground so that all the fibres of its root, a b c c, having struck back into the internal parts of the stem and of the leaves, may be reversed inwards; we shall then have the figure B, in which the part subjected to the light perfectly encompasses that subjected to the earth; and a b appears as the alimentary duct; b, as the cavity of the stomach, and c c as the vessels for distributing the sap.

Here we observe how very much in this metamorphosis the plant has assumed the type of the animal body, such as we observe it among the lower classes of animals. In this way we may now see why in the Medusa, the Sea-star, the Echinus, and other inferior kinds of animals, the aperture of the mouth is turned downwards, and the alimentary duct upwards ; or in this way we may see that the lower classes want the opposite or posterior opening of the excretory ducts (anus), or that (as is likewise particularly evident in the Medusa ) the vascular organs branch out immediately from the cavity of the stomach, and that the leaf-formed parts B, α α, furnish an explanation of the appearance of a kind of