THE PHENOMENA OF LIFE. 21 



than in vegetables, but there are many animals in which traces of it may 

 be discovered, and some, the Ascidians, in which it is found in consider- 

 able quantity. The presence of starch in vegetable cells is very charac- 

 teristic, though, as we have seen above, it is not distinctive, and a sub- 

 stance, glycogen, similar in composition to starch, is very common in the 

 organs and tissues of animals. 



(4.) Inherent power of movement is a quality which we so commonly 

 consider an essential indication of animal nature, that it is difficult tit 

 first to conceive it existing in any other. The capability of simple mo- 

 tion is now known, however, to exist in so many vegetable forms, that 

 it can no longer be held as an essential distinction between them and 

 animals, and ceases to be a mark by which the one can be distinguished 

 from the other. Thus the zoospores of many of the Cryptogamia ex- 

 hibit ciliary or amoeboid movements of a like kind to those seen in 

 amoebae; and even among the higher orders of plants, many, e.g., Dioncea 

 Muscipula (Venus's fly-trap), and Mimosa sensitiva (Sensitive plant), ex- 

 hibit such motion, either at regular times, or on the application of 

 external irritation, as might lead one, were this fact taken by itself, to 

 regard them as sentient beings. Inherent power of movement, then, 

 although especially characteristic of animal nature, is, when taken by 

 itself, no proof of it. 



