266 FOUNDATIONS OF BIOLOGY 



embryonic development or later. The individual's environ- 

 ment, food, friends, enemies, the world as he finds it, on the 

 one hand, and on the other his education, work, and general 

 reactions to this environment, all have their influence on 

 body and mind arid determine to a considerable extent the 

 realization of the possibilities derived from the germ 

 what he makes of his endowment. He acquires, let us say, 

 the strong arm of the blacksmith, the sensitive fingers of 

 the violinist, or the command of higher mathematics. In 

 other words, what he is depends on his heritage and what he 

 does with it. Now, if he does develop an inherited capacity, 

 .can he transmit to his offspring this talent in a more highly 

 developed form than he himself received it? Or, must his 

 children begin at the same rung of the ladder at which he 

 started and make their own way in the world? This is the 

 old question of the inheritance of modifications, or so-called 

 ACQUIRED CHARACTERS. Is the length of the* Giraffe's neck, 

 to take a classic though crude example, due to a stretching 

 toward the branches of trees during many successive 

 generations, with the result that a slight increment has been 

 gained in each generation and inherited by the following? 



We cannot enter into a discussion of the problem here, but 

 must simply assure the reader that the general consensus of 

 opinion of biologists is certainly to the effect that modifica- 

 tions, or changes in the individual body due to nurture, use 

 and disuse, are not transmitted as such. This conclusion is 

 held chiefly because there is no positive and much negative 

 evidence forthcoming, and also because there is no known 

 mechanism by which a specific modification of the soma can 

 so influence the germ complex that this modification will be 

 reproduced as such or in any representative degree. How- 

 ever, it should be emphasized that biologists in general recog- 

 nize the potent influence of environment and the organisms' 



