230 THE NATURE AND ORIGIN OF LIFE 



genital parasite 1 has an influence on the body which it 

 inhabits, the body, on its side, has an influence on the genital 

 parasite by determining the sexual direction in which it 

 matures. The question of the nature and determination 

 of the body's sex is much disputed. We apply the term 

 " secondary sexual characters " to all characters appearing 

 in the body under the influence of the genital organ and 

 made to disappear by castration, when this takes place at 

 a sufficiently precocious stage. 



1 I speak of a genital parasite on account of what has previously 

 been said that the genital organ may be compared with the pro- 

 thallus. 



