92 PETER OKKELBERG 



ferenziert sind und die verschiedenen Chromosomenzahl, die sie 

 erhalten, nur die Folge da von ist." 



Another line of investigation on hermaphroditism is the study 

 of the segregation of the germ cells in the sex gland. In the 

 case of Sagitta, Elpatewskj^ ('09, '10) finds a body in the cyto- 

 plasm of the cells during early cleavages, which he calls the 'beson- 

 dere Korper.' This is retained by only one cell after each cleav- 

 age up to the sixth, when it divides during mitosis and part of it 

 passes to each of the resulting cells. These two cells become the 

 germ cells, and Elpatewsky believes that one becomes the fore- 

 runner of the spermatozoa and the other of ova, and that the 

 former gets a larger portion of the 'besondere Korper.' Ancel 

 ('03) has worked on the early development of the germ cells in 

 Helix pomatia and thinks that three kinds of cells appear in the 

 germ gland, spermatozoa, oocytes, and nurse cells. He thinks 

 that the primordial germ cells become transformed into female 

 and male elements according to whether or not the nurse cells 

 are present at the time of transformation. Buresch ('11) thinks 

 that in Helix arbustorum, also, the fate of the indifferent germ 

 cell depends on its proximity to a nurse cell. The cases which 

 have been cited, show that the differentiation of the germ cells 

 into male and female cells has been interpreted as being due to 

 nuclear differences in some cases, cytoplasmic differences in 

 others, and to differences in the environment of the cells in still 

 other cases. If we conceive of sex as a metabohc state rather 

 than the result of definite sex factors, it is easy to see how any 

 one of the above factors might result in a metabolic change 

 which would throw the balance in favor of one or the other sex. 



It is unfortunate that so little work has been done on the history 

 of the germ cells in hermaphroditic animals; for it is in these 

 forms that one undoubtedly must look for valuable clues to the 

 problem of sex determination. 



c. The effect of delayed fertiUzation on sex. An interesting 

 case in which sex metabolism seems to be disturbed by outside 

 factors is that of the frog in which delayed fertihzation results 

 in the development of the eggs into male individuals exclusively. 

 It was found both by R. Hertwig ('05. '06, '07), and by Kuscha- 



