128 An Examination of Weismannism. 



characters produced by the direct influence of 

 climate" — i.e.. an exactly representative copying in 

 progeny of characters acquired by parents. I have 

 already quoted these words in order to show their 

 logical inadmissibility as used by Weismann. He 

 cannot be allowed thus to entertain the Lamarckian 

 factors and at the same time to maintain his theory 

 of germ-plasm, which excludes them as physiologically 

 impossible. Doubtless he was himself aware of this, 

 for he immediately added that " new experiments will 

 be necessary to afford the true explanation V 



The explanation, however, which he now gives is 

 not based on any new experiments, but on a new 

 suggestion to the effect that all such seemingly 

 conclusive instances of the inheritance of acquired 

 characters are, in truth, illusory. This suggestion is 

 that " Many climatic variations may be due wholly 

 or in part to the simultaneous variation of corre- 

 sponding determinants in some parts of the soma, and 

 in the germ-plasm of the reproductive cells. 2 " For 

 example, if, as Weismann now supposes, determinants 

 of the same kinds occur in the somatic tissues as well 

 as in the germ-cells, when a particular spot occurs on 

 a butterfly's wing, it has been due to a particular kind 

 of determinant which in the course of ontogeny was 

 transmitted from the germ-cell for the express purpose 

 of controlling the size and colour of the spot. But 

 a residue of precisely similar determinants was re- 

 served in the germ-cell (germ-plasm), for the purpose 

 of determining a precisely similar spot in the next 

 generation. Hence, if a rise of temperature, or any 

 other external change, is capable of so acting on the 



1 Essays, vol. i p. 101. Italics mine. 2 The Germ-plasm, p. 406. 



