162 THE CHILD AND HEREDITY 



not entitled to regard any conclusion as certain. But I 

 believe that upon the whole the direction in which com- 

 petent opinion strongly tends is towards the denial of the 

 inheritance of such acquired characters. It is very doubt- 

 ful if new characters can be acquired at all. Probably, as 

 Weismann says, "Every acquired character is jimply the 

 reaction of tl^aram^j^o_n_j u ^rtain^imulus. >> "No 

 organ can be originated by exercise," says another biologist, 



though an existing organ may be developed to its maxi- 

 mum." . . . And even, "granting that there are such 

 things as acquired characteristics, the evidence of their 

 transmission is unreliable." x 



But if biological evidence tends towards denying the 

 inheritance of acquired characters, it is not to be assumed 

 that it also tends to minimise the significance of heredity. 

 On the contrary, those who are the most strenuous in 

 denying that acquired modifications of the parental struc- 

 ture can be transmitted to the offspring make the largest 

 claims for the inheritance of other characters. Heredity, 

 they think, can be explained only on the theory of the 

 germ-plasm ; and the theory of the germ-plasm implies, 

 in the last resort, not only that life is continuous but that 

 from the first it contains, in some way, the tendency towards 

 the variations which reveal themselves in the successive 

 stages of animal life. Outward environment only elicits 

 or restrains, stimulates or represses, what is already present ; 

 but it can add nothing that is new. 



When the environment appears to cause a change in an 



organism, closer investigation shows that it furnishes only 



the occasion by reference to which the living thing changes 



itself. "A green frog, if he is not among green leaves, 



1 Headley's Problems of Evolution, p. 67. 



