GERM CELLS OF HERMAPHRODITES 205 



The investigators whose results have been de- 

 scribed above have thus furnished three theories re- 

 garding the differentiation of male and female germ 

 cells in hermaphrodites : (1) In Sagitta, according 

 to Elpatiewsky, it is an unequal distribution of the 

 **besondere Korper," (2) in Helix, according to Ancel 

 and Buresch, it is due to the presence or absence of a 

 nurse cell in the immediate neighborhood, and (3) in 

 Helix, Demoll considers it a result of the influence of 

 the accessory chromosome. It is perfectly obvious 

 that hermaphrodites offer exceptionally fine material 

 for the study of the differentiation of germ cells, but 

 that thus far the results have not furnished an ade- 

 quate explanation of the phenomenon. The investi- 

 gations of Boveri (1911), Schleip (1911), and Krueger 

 (1912) on the chromosomes in hermaphroditic nema- 

 todes may be discussed more profitably during the 

 consideration of the chromosome cycle in the next 

 chapter. 



Certain morphological and experimental studies 

 on the germ glands of amphibians are of interest be- 

 cause both oogonia and spermatogonia are sometimes 

 more or less closely associated in a single individual 

 during the developmental stages, and may persist 

 even in the adult germ glands of a number of species 

 which are commonly considered dioecious. Pfluger, 

 for example, was able to separate the young of the 

 frog, Rana temporaria, into three groups, males, fe- 

 males, and hermaphrodites ; the hermaphrodites 

 developed into either males or females. Similar 

 results were obtained by Schmidt -Marcel (1908) 



