Characters, Hereditary and Acquired. 57 



Probably enough has now been said to show that 

 the Neo- Darwinian assumption precludes the possi- 

 bility of its own disproof from any of the facts of 

 nature (as distinguished from domestication) and 

 this even supposing that the assumption be false. On 

 the other hand, of course, it equally precludes the 

 possibility of its own proof; and therefore it is as 

 idle in Darwinists to challenge Weismann for proof of 

 his negative (i.e. that acquired characters are not trans- 

 mitted), 'as it is in Weismann to challenge Darwinists 

 for proof of the opposite negative (i. e. that all 

 seeming cases of such transmission are not due to 

 natural selection). This dead-lock arises from the 

 fact that in nature it is beyond the power of the 

 followers of Darwin to exclude the abstract possi- 

 bility of natural selection in any given case, while it is 

 equally beyond the power of the followers of Weismann 

 to exclude the abstract possibility of Lamarckian 

 principles. Therefore at present the question must 

 remain for the most part a matter of opinion, based 

 upon general reasoning as distinguished from special 

 facts or crucial experiments. The evidence available 

 on either side is presumptive, not demonstrative 1 . 

 But it is to be hoped that in the future, when time 

 shall have been allowed for the performance of definite 

 experiments on a number of generations of domesti- 

 cated plants or animals, intentionally shielded from 

 the influences of natural selection while exposed to 

 those of the Lamarckian principles, results will be 



onus rests as much with him as with his opponents ; while, even if 

 his opponents are light, he elsewhere recognizes that they can bring 

 "actual proofs" of the fact only as a result of experiments which 

 must take many years to perform. 

 i Note A. 



