SPECIES AND THEIR ORIGIN .517 



(the enormous overproduction of individuals, and 

 consequent elimination) are incontrovertible. 



Lamarck's Theory. - - We have seen, in a previous 

 chapter, that one of the fundamental qualities of 

 living matter is that of response, and that environ- 

 mental stimuli frequently call forth advantageous 

 reactions (such as the callusing of the hand through 

 friction). That the reaction may also be disad- 

 vantageous is, of course, equally true. Moreover, 

 the fact that the organism is, as a rule, exquisitely 

 adapted to the particular environment in which 

 it is found is one of the most conspicuous facts of 

 nature. Lamarck contended that the continued 

 effect of such response made its impression on the 

 inheritance of the organism, or, to use a technical 

 phrase, that such " acquired characters " are in- 

 herited. Use and disuse thus play a large part in 

 Lamarck's theory. From another standpoint, the 

 will of the organism came into play, since he held 

 that the need for the development of an organ is a 

 causative factor in its production. Swimming birds 

 acquired their web feet by spreading their toes to 

 avoid sinking in the mud ; the giraffe, its long neck 

 by the inherited effect of generations of stretching 

 after the leaves of trees. Of course plants are 

 equally as well adapted to their environment as are 

 animals, but any question of use and disuse, or 

 particularly of such a psychical factor as need, must 

 be ruled out in the case of plants. Lamarck, in this 

 case, laid especial emphasis upon such factors as 

 light, heat, moisture, etc. 



