CHAPTER VII 



MANY of the most interesting biological problems 

 are those connected with the phenomenon of sex. 

 The term "sex" is applied to the soma or body of an 

 organism ; it indicates the presence of certain mor- 

 phological and physiological characteristics, which 

 may be separated into primary and secondary sexual 

 characters. The primary sexual characters are those 

 immediately connected with the reproductive organs ; 

 the secondary sexual characters, such as the beard of 

 man, the brilliant feathers and beautiful songs of 

 many male birds, and the antlers of the moose, repre- 

 sent differences between male and female individuals 

 not directly concerned with the production of germ 

 cells. It is customary to speak of male germ cells 

 and female germ cells; this is not strictly proper, 

 since in only a few special cases can we predict the 

 sex of the individual which will develop from an egg. 

 Moreover, every germ cell must contain the poten- 

 tiality of both sexes since sooner or later its descend- 

 ants will give rise, some to male, some to female or 

 perhaps to hermaphroditic offspring. Thus the egg 

 is an initial hermaphrodite ; it may or may not be- 

 come an eventual hermaphrodite according to the sex- 

 ual condition of the individual to which it gives rise. 



189 



