56 Darwin, and after Darwin. 



In this way apparently useless characters, as well as 

 obviously useful ones, are ruled out of the question : 

 that is to say, all hereditary characters of species in 

 a state of nature are assumed to be due to natural 

 selection, and then it is demanded that the validity of 

 this assumption should be disproved by anybody who 

 doubts it. Yet Weismann himself would be unable 

 to suggest any conceivable method by which it can 

 be disproved among species in a state of nature and 

 this even supposing that the assumption is entirely 

 false \ 



Consequently, the only way in which these 

 speciously-sounding challenges can be adequately met 

 is by removing some individuals of a species from 

 a state of nature, and so from all known influences 

 of natural selection ; then, while carefully avoiding 

 artificial selection, causing these individuals and their 

 progeny through many generations unduly to exer- 

 cise some parts of their bodies, or unduly to fail in 

 the exercise of others. But, clearly, such an experi- 

 ment is one that must take years to perform, and 

 therefore it is now too early in the day to reproach 

 the followers of Darwin with not having met the 

 challenges which are thrown down by the followers 

 of Weismann 2 . 



1 In subsequent chapters, especially devoted to the question (i.e. 

 Section II), the validity of this assumption will be considered on 

 its own merits. 



I say " the followers of Weismann," because Weismann himself, with 

 his clear perception of the reqnircmentsof experimental research, expressly 

 states the above considerations, with the conclusions to which they 

 lead. Nevertheless, he is not consistent in hi* utterances upon this 

 matter ; for he frequently expresses himself to the effect, " that the onus 

 probandi rests with my opponents, and therefore they ought to bring 

 forward actual proofs " (Essays, i. p. 390). But, as above shown, the 



