INTRODUCTORY 9 



aftenvards to become famous in this connection, 

 Lamarck published his " Philosophie Zoologique," 

 a work in which precise expression was given to 

 the views which Erasmus Darwin and others had 

 merely adumbrated. Lamarck not only declared 

 that animal and vegetable species were cousins, so 

 to speak, but he stated a theory which* proposed to 

 explain the manner in which they came to change. 

 His survey of the facts showed him that living 

 things, in the course of their individual history, 

 undergo modifications in response to what he called 

 the " milieu environnant," or, as we now say, the 

 environment. To take a simple case, the ancestral 

 giraffe found itself in a land where succulent and 

 palatable leaves grew upon the lowermost branches 

 of tall trees. By an effort the giraffe could just 

 reach the lowest of these leaves. In course of time, 

 then, the giraffe's neck would undergo some elonga- 

 tion, just as the pianist's fingers become capable of 

 unusually wide separation ; and the lengthened neck 

 of the giraffe — or rather the ancestor of the giraffe — 

 would be reproduced in its offspring. The character 

 acquired by the giraffe in response to the demands 

 of the environment would be perpetuated. Each 

 generation would transmit a slightly longer neck 

 than the last, until finally there appeared the giraffe 

 we know. 1 Such was the theory of Lamarck; but 

 it made little impression or none upon his contem- 

 poraries. The theory of organic evolution was to be 



1 Long though the giraffe's neck is, it yet contains only seven 

 vertebrae, the same number as are found in the neck of man and 

 all other mammals save two. The fact obviously points to a 

 common ancestry for all mammals. 



