DE GEN ERA TION. 



389 



teristically in every leaf. Through the combined oj)eration of this 

 green color either singly or aided by the leaf -protoplasm and the 

 action of light, plants decompose the carbonic acid of the air, as every 

 schoolboy knows, and, retaining the carbon to aid in the formation of 



Fig. 18. Hydile. (Iu both figures young hydrse are represented budding from the side of the 



parent). 



starch, set free the oxygen, which thus returns to the atmosphere, and 

 is welcomed by the animal hosts. The hydra, or common fresh-water 

 polyp (Fig. 18), many animalcules, and certain worms of a low type, 

 possess this chlorophyl. Like dishonest manufacturers, they seem to 

 have infringed the patent-rights of the j)lant to 

 elaborate this green color. And it is no longer 

 matter of theory, but ascertained fact, that these 

 green animals are capable, like the plants, of ab- 

 sorbing carbonic acid usually a fatal gas to the 

 animal constitution and of elaborating starch 

 therefrom like their plant neighbors. Thus a 

 simpler mode of feeding, ob- 

 viating the necessities of animal 

 existence in the way of diges- 

 tive apparatus, has apparently 

 led to the simplification of 

 structure. Degeneration has 

 followed in the worms just 

 mentioned, as the result of 

 their imitation and acquirement 

 of vegetative powers of feed- 

 ing ; and it is probable that 

 other alterations in the way of 

 dietary, of less sweeping char- 

 acter than that just mentioned, 

 will affect, in like retrogressive 

 fashion, the animal constitution. 



Some of the most curious cases of degeneration known to us illus- 

 trate the total disappearance of digestive apparatus even in some 

 beings, in which, as in the stylops already mentioned, one sex becomes 



Fig. 19. Kotifera. 



