122 ORIGIN OF SOMATIC 



which alone have an adaptive relation to the sexual 

 or reproductive habits of the animal are also 

 the only characters which are influenced by the 

 hormones of the reproductive organs ? The idea 

 of mutations implies neither an external relation 

 nor an internal relation in the organ or character; 

 but these characters have both, the external relation 

 in the function they perform in the sexual life of 

 the individual, the internal relation in the fact that 

 their development is affected by the sexual hor- 

 mones. There is no more striking example of the 

 inadequacy of the current conceptions of Mendelism 

 and mutation to cover the facts of bionomics and 

 evolution. 



The truth is that facts and experiments within 

 a somewhat narrow field have assumed too much 

 importance in recent biological research. No 

 increase in the number of facts or experimental 

 results of a particular class will compensate for the 

 want of sound reasoning and a comprehensive 

 grasp of the phenomena to be explained. The co- 

 existence of the external and the internal relation in 

 the characters we are considering suggests that one 

 is the cause of the other, and as it is obvious that the 

 relation for instance of a stag's antlers to a testicular 

 hormone could not very well be the cause of the use 

 of the antlers in fighting, the reasonable suggestion 

 is that the latter is the cause of the former. We have 

 already seen that the development and shedding 

 of the antler are processes of essentially the same 

 kind physiologically, or pathologically, as these 

 which can be and are occasionally produced in the 

 individual soma by mechanical stimulus and injury 

 to the periosteum. The fact that a hormone from 



