40 SEXUAL DIMORPHISM 



presence or absence of the germ-cells which are to give rise 

 to the following generation. It is conceivable that the activity 

 of one or the other set of determinants in somatic tissues 

 should be called forth by external stimuli, such as tempera- 

 ture or irritation, the determinants themselves arising only 

 in the germ. But it is not conceivable, on Weismann's 

 hypothesis, that the removal of the testes in the young animal 

 should affect the behaviour of the determinants for the antlers 

 in later life, for according to the hypothesis there is no 

 continuity between the testes and the somatic cells. And it 

 is obvious that if the removal of the testes can affect the 

 development of tissues in the head, the development 

 of the latter may affect the properties of the testes. To 

 my thinking, the suppression of male characters in con- 

 sequence of castration is in itself sufficient to disprove 

 the theory of the absolute continuity of the germ-plasm, and 

 its absolute independence of the somatic cells. If, as Weis- 

 mann supposed, the germ-cells were entirely unaffected in 

 their essential properties by the history and circumstances of 

 the body in which they were contained, it is impossible to 

 conceive how the removal of the generative organs could 

 affect the development of the tissues of that body. 



Another interesting point which gives remarkable support 

 to the view here advocated is that the existence of secondary 

 sexual characters is, in many cases, not merely limited to 

 the period of mature life, but actually to that part of the 

 year in which the reproductive organs are active, that is to 

 the breeding season. It is a familiar fact that this is the 

 case with the antlers of the stags, which drop off in the early 

 part of the year and are developed again in summer. The 

 rutting season of stags occurs in autumn, and it is only 

 during this season that they consort with the females and 

 engage in fights with other stags. If the antlers were 

 originally outgrowths of bone produced by the pressure of 



