314 Habit and Instinct. 



whether the adaptation be reached through individual modi- 

 fication of the bodily tissues or through racial variation of 

 germinal origin. So long as the adaptation is there — no 

 matter how it originated — that is sufficient to secure sur- 

 vival. Professor Weismann applies this conception to one 

 of those difficulties which have been urged by critics of 

 natural selection. "Let us take," he says,* "the well- 

 known instance of the gradual increase in development of 

 the deer's antlers, in consequence of which the head, in 

 the course of generations, has become more and more 

 heavily loaded. The question has been asked as to how 

 it is possible for the parts of the body which have to 

 support and move this weight to vary simultaneously and 

 harmoniously if there is no such thing as the transmission 

 of the effects of use or disuse, and if the changes have 

 resulted from processes of selection only. This is the 

 question put by Herbert Spencer as to ' co-adaptation,' and 

 the answer is to be found in connection with the process 

 of intra-selection. It is by no means necessary that all 

 the parts concerned — skull, muscles, and ligaments of the 

 neck, cervical vertebrae, bones of the fore limbs, etc. — 

 should simultaneously adapt themselves by variation of the 

 germ to the increase of the size of the antlers; for in 

 each separate individual the necessary adaptation will be 

 temporarily accomplished by intra-selection," that is, by 

 individual modification due to the innate plasticity of the 

 parts concerned. "The improvement of the parts in 

 question," Professor Weismann urges, "when so acquired, 

 will certainly not be transmitted, but yet the primary 

 variation is not lost. Thus when an advantageous increase 

 in the size of the antlers has taken place, it does not lead 

 to the destruction of the animal in consequence of other 

 parts being unable to suit themselves to it. All parts of 



* Romanes Lecture, pp. 18, 19. 



