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 
