168 DARWINISM AND HUMAN LIFE 



argued that there are some adaptive characters 

 which cannot be readily interpreted in terms 

 of natural selection (as is imphed in the appeal 

 of some Neo-Darwinians to " intra-selection," 

 " germinal selection," and so on), and that therefore 

 natural selection cannot be regarded as a generally 

 acting factor. Moreover, the Neo-Lamarckian is 

 at liberty to reply that he does not regard the 

 modification-inheritance theory as appUcable to 

 all possible cases. 



Importance of Environment and Function 

 Remains. — ^Although bodily changes due to 

 changes in environment or in function may not 

 be transmissible, the importance of these influences 

 remains. (1) An inheritance cannot be realised 

 without an environment, any more than a man 

 whose legacy was a cheque could make much of 

 it without a bank. (2) Changes in environment 

 and function, saturating through the body, may 

 stimulate the variabiUty of the germ-plasm. This 

 may be the cause of mutation. (3) Living creatures 

 are in many cases very plastic, and their modifica- 

 tions are often of great individual importance, 

 and may even preserve the life. (4) The secondary 

 effects of modifications may reach and influence 

 the germ-cells. (5) Every one admits that the 

 state of the maternal constitution is very important 

 in all cases where there is an intimate connection 

 between the mother and the unborn young. 



Selection and Stimulus. — In two other ways 

 changes in the conditions of life are of great im- 

 portance : they form part of the mechanism of 

 selection, whereby the relatively less fit variants 

 are quickly or slowly, roughly or gently, eliminated, 

 and they act as a stimulus to the intrinsic self- 



