74 ORGANIC EVOLUTION 



than he would have had if the father, through inactivity, 

 had allowed his capacity for strength to lie undeveloped ? 

 There is little, if any, carefully scrutinized and carefully 

 recorded evidence in favor of an affirmative answer. 



How can we test the case ? It is very difficult. Experi- 

 mentation has failed to show inheritance of the effects of use 

 and disuse among the higher plants and animals, and we 

 have practically no evidence in its favor except its apparent 

 plausibility. But, when carefully scrutinized, is it as plausible 

 as it seems at first thought? How can the use of the biceps 

 muscle in the arm of the parent so affect the offspring that 

 he will be not only stronger, but stronger in the biceps 

 muscle, the particular part affected in the parent? The child 

 is not the child of the biceps muscle of the parent, but the 

 child of the germ cells of the parent, and these germ cells 

 have little to do with the parent's biceps muscle. They are 

 separated by a great space, and they do not, so far as we 

 know, have any special mutual relation. If the increased 

 strength gained by the biceps muscle of the parent is to be 

 handed down to the offspring, the increase in size in the 

 parent's biceps must in some way produce an effect upon 

 the parent's distant germ cells from which the child is to 

 develop; and this effect upon the germ cells must be of so 

 particular and definite a kind as to produce not a general 

 effect upon the offspring but a particular effect, namely, 

 greater strength, and not only greater strength, but greater 

 strength in a particular portion of the body, the biceps muscle 

 of the right arm. The hypothesis, apparently so simple at 

 first glance, is seen, when scrutinized, to involve a connection 

 between muscle cells and the distant srerm cells so intimate 



O 



and so definite as to be marvellous beyond almost any known 



