PHENOMENA OF INHERITANCE 275 



of the spermatozoa receive such a determiner, 

 the other half of them being without it. If 

 then, an egg is fertilized by a sperm without 

 one of these determiners, a male results; but 

 if an egg is fertilized by a sperm with one of 

 these determiners, a female is produced. This 

 is graphically represented in Fig. 58 in 

 which X represents the sex-determiner, which 

 is duplex in the female and simplex in the 

 male, and the chance unions of male and fe- 

 male gametes yield females (XX) and males 

 (XO) in equal numbers. 



In either sex many secondary sexual charac- 

 ters of the other sex are present during de- 

 velopment, and traces of these may persist in 

 the adult; but one set of these characters de- 

 velops in the male and another in the female, so 

 that they may be called sex-limited. The de- 

 velopment of the secondary sex characters is 

 usually determined by the ovaries or testes, 

 which are the primary sex characters, though 

 in some instances they may develop in animals 

 which have lost their ovaries or testes, but in 

 the last analysis both primary and secondary 

 sex characters are dependent upon the sex- 



