108 CREATIVE EVOLUTION [chap. 



portance to the presence of special characters than to their 

 tendency to develop, and if we regard as essential that 

 tendency along which evolution has been able to continue 

 indefinitely, we may say that vegetables are distinguished 

 from animals by their power of creating organic matter 

 out of mineral elements which they draw directly from the 

 air and earth and water. But now we come to another 

 difference, deeper than this, though not unconnected with it. 

 The animal, being unable to fix directly the carbon 

 and nitrogen which are everywhere to be found, has to 

 seek for its nourishment vegetables which have already 

 fixed these elements, or animals which have taken them 

 from the vegetable kingdom. So the animal must be 

 able to move. From the amoeba, which thrusts out 

 its pseudopodia at random to seize the organic matter 

 scattered in a drop of water, up to the higher animals 

 which have sense-organs with which to recognize their 

 prey, locomotor organs to go and seize it, and a nervous 

 system to coordinate their movements with their sen- 

 sations, animal life is characterized, in its general direction, 

 by mobility in space. In its most rudimentary form, the 

 animal is a tiny mass of protoplasm enveloped at most 

 in a thin albuminous pellicle which allows full freedom for 

 change of shape and movement. The vegetable cell, 

 on the contrary, is surrounded by a membrane of cellu- 

 lose, which condemns it to immobility. And, from the 

 bottom to the top of the vegetable kingdom, there are the 

 same habits growing more and more sedentary, the plant 

 having no need to move, and finding around it, in the air 

 and water and soil in which it is placed, the mineral ele- 

 ments it can appropriate directly. It is true that phe- 

 nomena of movement are seen in plants. Darwin has 

 written a well-known work on the movements of climbing 

 plants. He studied also the contrivances of certain in- 



