ii THE PLANT AND THE ANIMAL in 



inspiring them, and raise discussions to which the 

 present state of science does not admit of a final 

 settlement. But a comparison of the different solutions 

 shows that the controversy bears less on the main lines 

 of the movement than on matters of detail ; and so, by 

 following the main lines as closely as possible, we shall 

 be sure of not going astray. Moreover, they alone 

 are important to us ; for we do not aim, like the 

 naturalist, at finding the order of succession of 

 different species, but only at defining the principal 

 directions of their evolution. And not all of these 

 directions have the same interest for us : what concerns 

 us particularly is the path that leads to man. We shall 

 therefore not lose sight of the fact, in following one 

 direction and another, that our main business is to 

 determine the relation of man to the animal kingdom, 

 and the place of the animal kingdom itself in the 

 organized world as a whole. 



To begin with the second point, let us say that no 

 definite characteristic distinguishes the plant from the 

 animal. Attempts to define the two kingdoms strictly 

 have always come to naught. There is not a single 

 property of vegetable life that is not found, in some 

 degree, in certain animals ; 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 enamoured of clean- 

 cut concepts have regarded the distinction between the 

 two kingdoms as artificial. They would be right, if 



O / O 



definition in this case must be made, as in the mathe 

 matical and physical sciences, according to certain 

 statical attributes which belong to the object defined 

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



