194 SCIENCE PROGRESS 



are distinguished and named which live in the same district under 

 the same conditions, and that where they live in different habitats 

 there is no evidence that the characters correspond with differ- 

 ences in the mode of life. On the other hand, there is no reason 

 why a single species should not become adapted to some 

 peculiar mode of life, but then it would be a matter of opinion 

 among systematists whether it should not be placed in a 

 separate genus. 



Before proceeding further with this part of the subject it 

 is interesting to consider the origin and nature of these 

 adaptations. While others have been disputing whether 

 acquired characters are ever inherited and whether adaptations 

 are due to the inheritance of acquired characters, Dr. Archdall 

 Reid has made the brilliant discovery that such adaptations 

 as those which distinguish man from the anthropoid apes are 

 not inherited at all but are acquired by every individual in the 

 course of his development. Inborn or congenital characters, he 

 says, are developed by the stimulus of nutrition alone, acquired 

 characters are developed by the stimulus of use. Modifications 

 acquired as a result of use and disuse are clearly never trans- 

 mitted, because they never develop except in 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 of 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 man- 

 hood 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 importance 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 acquirement but in hereditary con- 

 stitution. 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 



1 Principles of Heredity* 2nd Edit., London, 1906, p. 35. 



