320 STUDIES, SCIENTIFIC AND SOCIAL 



forward in its favour, together with the reasons I shall 

 give for the inadequacy of those arguments. For it must 

 always be remembered that the inheritance of this class 

 of characters or qualities must be proved by facts that 

 admit of no other interpretation, if it is to be accepted as 

 one of the bases of the theory of organic evolution. When 

 such tremendous issues are at stake we cannot base our 

 faith upon probabilities, unless they are to an overwhelm- 

 ing degree greater than the probabilities on the other 

 side. 



I propose to waste no time on the question whether 

 mutilations are ever inherited, because both parties are 

 now agreed that this is not the point at issue. What we 

 want to know is, whether the effects produced during the 

 lives of individuals by such natural causes as the use or 

 disuse of certain muscles or organs, change of food, or 

 change of climate, are transmitted to offspring, so as to 

 accumulate such effects and thus serve as an important 

 factor in evolution. 



Argument from Habits and Instincts. 



Two of the cases which have been adduced as affording 

 very strong evidence of the inheritance of an acquired 

 character are, the habit of dogs to turn round several 

 times before lying down, and the peculiar play-habits of 

 the bower-birds ; these being supposed to be beyond the 

 power of natural selection to produce, because neither 

 are of vital importance to the species. But such cases as 

 these really prove nothing, because so much in them is 

 hypothetical. It is only guessed that the dog's habit is 

 derived from wild dogs turning round to make a comfort- 

 able bed in rough grass. But even if this be a fact, there 

 are many awned seeds of grasses which prick the skin, and 

 in some cases work their way into the body, causing 

 wounds or death, and the turning round may have the 

 effect of laying these awned seeds parallel to the hairs and 

 thus prevent them from penetrating the skin. If so, 

 natural selection would produce and preserve the habit. 

 Again, it may, with many dogs, be a matter of simple 



