ON DYNAMIC INFLUENCES IN EVOLUTION. 7 



opment than could ever have been expected from the unas 

 sisted working of the physical forces. 



Passing from these general considerations to those of a more 

 special character, the contention of Weismann that ''not a 

 single fact hitherto brought forward can be accepted as proof ' ' 

 of the transmission of acquired characters demands attention. 

 This reminds one of the familiar statement of twenty years 

 ago that the Darwinians had not brought forward a single in 

 stance of the conversion of one species into another species. 

 If the Dynamic Bvolutionist brings forward an hypothesis 

 which explains the facts of nature without violence to sound 

 reasoning, that hypothesis is entitled to respect and considera 

 tion until some -better one is proposed or some vitiating error 

 is detected in it. No one has yet ' ' proved ' ' that one species 

 is developed out of another species in the sense in which 

 Weismann uses the word proof in his criticism. But plenty of 

 facts which support the hypothesis that acquired characters are 

 transmitted in the sense hereinbefore explained have been ac 

 cumulated, of which Osborne's paper, above cited, affords evi 

 dence in one direction. Can anyone believe that the perma 

 nent limb-callosities of the horse and deer, for instance, are 

 selective developments of fortuitous larval corns ? Our knowl 

 edge of the physiology of any animal, except too or three 

 which have been domesticated for ages, and excepting man, is 

 so contemptibly meagre that it cannot be quoted as evidence 

 on either side. 



The question has been much obscured by the attempt to 

 quote the effect or non-effect of mutilations upon progeny, on 

 one side or the other. 



For the Dynamic hypothesis only those characters can be 

 considered which arise from permanent physiological reactions 

 due to the impact of external forces. Mutilations rarely fall 



