WITH VEGETABLES. 7 



even in their lowest forms ; for while the former consist 

 mainly of a substance containing carbon, hydrogen, and 

 oxygen only, arranged so as to form a compound closely 

 allied to starch, and called cellulose, the latter are com- 

 monly composed almost exclusively of the three elements 

 just named, together with a fourth, nitrogen, the proxi- 

 mate principles formed from these being identical, or 

 nearly so, with albumen. It must not be supposed, how- 

 ever, that either of these typical compounds alone, with 

 its allies, is confined to one kingdom of nature. Nitro- 

 genous or albuminous compounds are freely produced 

 by vegetable structures, although they form an infinitely 

 smaller proportion of the whole organism than cellulose 

 or starch. And while the presence of the latter in animals 

 is much more rare than is that of the former in vegetables, 

 there are many animals in which traces of it may be dis- 

 covered, and some, the Ascidians, in which it is found in 

 considerable quantity. 



Inherent power of movement is a quality which we 

 so commonly consider an essential indication of animal 

 nature, that it is difficult at first to conceive it as existing 

 in any other. The capability of simple motion 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 zoo- 

 spores of many of the Oryptogamia exhibit movements of 

 a like kind to those seen in animalcules ; and even 

 among the higher orders of plants, may exhibit 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 character- 

 istic of animal nature, is, when taken by itself, no proof 

 of it. Of course, if the movement were such as to 

 indicate any kind of purpose, whether of getting food or 



