THEIR LIFE AND AFFINITY. 



243 



under the influence of light ; wherefore, though sometimes fettered to 

 the earth, it is by no means fixed or rooted in it, to which circum- 

 stance 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 -\- above- 

 ground, 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 pos- 

 terior opening of the excretory ducts (anus), or that (as is likewise par- 

 ticularly evident in the Medusaf ) the vascular organs branch out imme- 

 diately from the cavity of the stomach, and that the leaf-formed parts 

 B, a a, furnish an explanation of the appearance of a kind of exter- 



* Cants, Lehrbuck der Zootomie, p. 327. 



t Ibid., p. 578. 



