284 Theories Treating of Inheritance 



of the necessity of regarding them as bound up with one 

 another into a rigid structure, he has been led, through 

 the conception of these preformistic germs which was 

 forced upon him by particulate inheritance, to deny most 

 energetically every possibility of the inheritance by the 

 germ of characters which the soma had acquired by 

 functional adaptation. 



Weismann admits, it is true, that sometimes external 

 influences acting uniformly upon the whole organism, like 

 temperature and other such things, can alter the deter- 

 minants of the soma and the corresponding determinants 

 of the germ at the same time and in the same direction; 

 as occurs for example in the determinants of the wing 

 scales of the butterfly Polyommatus phlaeas, whose color 

 changes as we have seen when it is transported to a 

 warmer climate. But the cases which permit of this ex- 

 planation, which resembles in many respects the above 

 discussed diplogenesis of Cope, the only cases which 

 Weismann admits, are limited by this investigator to so 

 small a number, and are also of so peculiar a kind that it 

 would be wrong to assert that he held less determinedly 

 to his earlier stand as an opponent of the Lamarckian 

 theory. 



We may point out however, the following contradic- 

 tions. He admits inheritance in unicellular organisms 

 while he denies it in the pluricellular and thinks he can 

 justify this by saying simply that as the unicellular divide 

 always into two equal halves they need only preserve 

 what they have acquired, in order to transmit it unaltered 

 to the new individuals. But this is not right. For new 

 functional adaptations acquired by the anterior end of the 

 infusorian Stentor, for instance the acquisition of "Mem- 

 branelles" by the peristome in consequence of the fusion 



