106 CREATIVE EVOLUTION [chap. 



come to naught. There is not a single property of vege- 

 table life that is not found, in some degree, in certain ani- 

 mals; not a single characteristic feature of the animal 

 that has not been seen in certain species or at certain 

 moments in the vegetable world. Naturally, therefore, 

 biologists enamored of clean-cut concepts have regarded 

 the distinction between the two kingdoms as artificial. 

 They would be right, if definition in this case must be made, 

 as in the mathematical and physical sciences, according 

 to certain statical attributes which belong to the object 

 defined and are not found in any other. Very different, in 

 our opinion, is the kind of definition which befits the 

 sciences of life. There is no manifestation of life which 

 does not contain, in a rudimentary state — either latent 

 or potential, — the essential characters of most other mani- 

 festations. The difference is in the proportions. But this 

 very difference of proportion will suffice to define the group, 

 if we can establish that it is not accidental, and that the 

 group as it evolves, tends more and more to emphasize these 

 particular characters. In a word, the group must not be 

 defined by the possession of certain characters, but by its 

 tendency to emphasize them. From this point of view, taking 

 tendencies rather than states into account, we find that 

 vegetables and animals may be precisely defined and 

 distinguished, and that they correspond to two divergent 

 developments of life. 



This divergence is shown, first, in the method of ali- 

 mentation. We know that the vegetable derives directly 

 from the air and water and soil the elements necessary 

 to maintain life, especially carbon and nitrogen, which it 

 takes in mineral form. The animal, on the contrary, 

 cannot assimilate these elements unless they have already 

 been fixed for it in organic substances by plants, or by 

 animals which directly or indirectly owe them to plants; 



