94 SEX INHERITANCE ' 



tion of F and M may be in hermaphroditic types, it is 

 less inconsistent to use the symbols for the sex chro- 

 mosomes as the symbols for the sex factors also, if 

 it is at the same time recognized that the whole 

 chromosome is not involved in determining sex. 



Hermaphroditism and Sex 



Typical hermaphrodites are individuals that ripen 

 both eggs and sperm. They are found widely repre- 

 sented in the plant and anim.al kingdoms, whole 

 orders and classes consisting almost entirely of such 

 individuals. Self-fertilization may occur, as in 

 many plants, but cross-fertilization between different 

 individuals appears more often to take place. In 

 addition to these typical cases, that call here for no 

 further comment, there are cases in which the in- 

 dividual may ripen first its sperm and later its eggs 

 (protandric hermaphroditism), or vice versa. There 

 are also several cases in which, in the j^oung stages, 

 eggs (or egg-like cells) appear in a gonad that is 

 found subsequently to function as a testis. In the 

 amphipod crustacean, Orchestia gammarillus, Bou- 

 lenger found that 198 out of 217 young males con- 

 tained ova, or egg-like cells, in the testes. In the 

 adult males these cells had almost completely dis- 

 appeared. In the male harvestman (Phalangium) 

 large cells, said to be eggs, have been found in the 

 testes. In the testes of the young male frog of some 

 species there are large egg-like cells in the testes 

 just prior to the time of metamorphosis. They 



