194 GERM-CELL CYCLE IN ANIMALS 



divide before the sperm nucleus fuses with it, the 

 latter may unite with one of the daughter nuclei 

 of the egg nucleus ; this cell with this double nucleus 

 might then produce female structures, whereas the 

 other cell with only a single nucleus representing one- 

 half of the egg nucleus might give rise to male char- 

 acters. Morgan has proposed another theory which 

 is based on the fact that more than one spermatozoon 

 is known to penetrate the eggs of insects. If one 

 of these supernumerary spermatozoa should chance 

 to divide, it might result in the formation of male 

 structures, whereas the cells containing descendants 

 of the egg nucleus fused with another sperm nucleus 

 would exhibit female characteristics. 



There is some evidence that true hermaphroditism 

 may exist among insects, at least during their embry- 

 onic and larval stages. Thus Heymons (1890) has 

 described in a young larva of the cockroach, Phyllo- 

 dromia gervianica, what appear to be rudimentary 

 egg-tubes, and in another larva eggs were found in 

 the testes which resembled those present in the egg- 

 tubes of female larvae of the same size (1 mm. in 

 length). More recently, Schonemund (1912) has 

 reported the presence of egg-tubes attached to the 

 anterior end of the testes of stone-fly nymphs {Perla 

 marginata) . 



True hermaphroditism is rare in man and other 

 mammals, but several cases have been described in 

 the pig by Sauerbeck (1909) and Pick (1914), and in 

 man by Simon (1903), Uffreduzzi (1910), Gudernatsch 

 (1911), and Pick (1914). 



