INTRODUCTION 39 



The activity of the testes does not leave the rest of the 

 body unaffected. On the contrary, it is associated with a 

 nervous exaltation which again influences the activities of 

 all the other organs. It was during this condition that the 

 secondary characters were originally produced. The special 

 processes of growth occur in subsequent generations by 

 heredity, when the body is in the same condition, not othervjise. 

 Thus we understand why it is that the antlers of the stag do 

 not develop in the female, and fail to develop perfectly in 

 the stag which is castrated. In either of these cases the 

 animal fails to reach the condition of body in which alone 

 the local hypertrophy can occur. On the other hand, it is not 

 to be doubted that the female inherits the tendency to 

 produce antlers. This is necessarily the case because the 

 female individual, like the male, arises from the union of 

 male and female germ-cells. It is also proved to be the case 

 by the fact that the female often transmits to her progeny 

 peculiarities in the secondary sexual characters of her own 

 father, and even occasionally, when old and no longer fertile, 

 develops to some extent such characters herself. 



The known phenomena of the frequent development of 

 male characters in aged females, and of the suppression of 

 the male characters in castrated males, compelled Weismann 

 to admit the presence of both male and female determinants, 

 not merely in the germ, but in the somatic cells of each 

 individual. He considered that thus under certain circum- 

 stances the latent set of determinants might become active 

 and manifest their effects. But he does not thus surmount 

 the difficulty presented to his theory. The question is, why 

 should the absence of the testes or the sterility of the ovaries 

 affect the activity of determinants in somatic cells ? Accord- 

 ing to Weismann's conceptions the behaviour of the somatic 

 cells is determined solely by the germ from which they 

 sprang, and in that case they cannot be affected by the 



