EVOLUTION OF MAN 33 



response to the same stimulation as in the parent : 

 " Plainly, then, that which is transmitted to the_ 

 infant is not the modification, but only the power o£ 

 acquiring the modification under similar circumstances' 

 — a power which has undergone such an evolution in 

 high animal organisms that in man, for instance, 

 nearly all the developmental changes which occur 

 between infancy and manhood are attributable to 

 it."* Now, while it must be admitted that it is very 

 important to ascertain how far characters are developed 

 entirely as the result of the constitution of the germ- 

 plasm, and how far they require an appropriate 

 stimulus, I think Dr. Reid attributes excessive im- 

 portance to the latter factor. We know that a child 

 only learns to speak by hearing speech, but we also 

 know that monkeys and dogs do not learn to speak 

 under the same conditions. The difference, therefore, 

 between man and his nearest allies is not in acquire- 

 ment, but in hereditary constitution. Indeed, Dr. 

 Reid admits as much, but he puts the fact in other 

 words, and here, as in much else that he has written, 

 it seems to me that he imagines he has discovered 

 something new when he has expressed what was 

 known before in different and unnecessarily abundant 

 language. He says that since " Nature " has en- 

 dowed animals with the power of making not all 

 possible acquirements, but only certain fixed acquire- 

 ments that are commonly useful to the species, there- 

 fore species differ not only in characters which are 

 inborn, but also in those which are acquired ; for 



'■^ Principles of Heredity, 2nd Edition, page 35. 



