Characters, Hereditary and Acquired. 141 



a partisan view to take. In any impartial survey 

 it should be seen that while the facts are fairly 

 interpretable on Weismann's theory, they are by 

 no means proof thereof. For any other theory of 

 Heredity must suppose the material of heredity to 

 be of a kind more or less specialized, and the 

 mechanism of heredity extremely precise and well 

 ordered. And this is all that the facts of karyo- 

 kinesis prove. Granting that they prove continuity, 

 they cannot be held to prove that continuity to 

 be absolute. In other words, the facts are by no 

 means incompatible with even a large amount of 

 commerce between germ-plasm and somato-plasm, or 

 a frequent transmission of acquired characters. 



Again, Weismann's theory, that the somatic and 

 the germ-plasm determinants may be similarly and 

 simultaneously modified by external conditions may 

 be extended much further than he has used it 

 himself, so as to exclude, or at any rate invalidate, 

 all evidence in favour of Lamarckianism, other than 

 the inheritance of the effects of use and disuse. All 

 evidence from apparently inherited effects produced 

 by change of external conditions is thus virtually 

 put out of court, leaving only evidence from the 

 apparently inherited effects of functionally produced 

 modifications. And this line of evidence is invalidated 

 by Panmixia. Hence there remain only the arguments 

 from selective value and co-adaptation. Weismann 

 meets these by adducing the case of neuter insects, 

 which have been already considered at sufficient 

 length. 



