GERM-CELL HISTORY IN THE BROOK LAMPREY 77 



came to the conclusion that, if intermediates were found in a 

 culture, all the individuals were intermediates and consequently 

 some developed into males and some into females. 



Witschi ('14) found that individuals of Rana temporaria that 

 had just metamorphosed showed all the intermediate conditions 

 between pure males and pure females. He believed that the 

 testis developed out of an ovary and not from an undifferentiated 

 gland. No evidence was found that an ovary developed out of 

 a testis; for, usually, when a germ gland had begun to develop 

 in the male direction, the whole or at least a part of it became 

 male. 



Witschi has advanced the idea that a germ cell in a frog becomes 

 a male or a female cell according to the length of time it remains 

 in the germinal epithelium. He found that when eggs developed 

 under optimum temperatures (21°C.), no hermaphrodites appeared 

 in the cultures; but when the eggs developed under low temper- 

 atures (10° to 15°C.) and under high temperatures (27°C.), inter- 

 mediates were formed. Witschi concludes that heat and cold 

 increase the chances of an early migration of some of the germ 

 cells out of the germinal epithelium into the sex cords, and that 

 when a part of the germ gland has thus once differentiated in the 

 male direction, the whole gland usually changes into a testis, 

 although the germ cells which remain in the germinal epithelium 

 transform into oocytes. Under this assumption there would nat- 

 urally be more males formed at either extreme of temperature. 

 In the same way Witschi assumes that overripeness of the egg at 

 fertilization so alters the trophic condition of the whole organism 

 that only males are produced. 



Abnormal temperatures and overripeness Witchi speaks of as 

 'Ausenfaktoren,' and claims that they may influence the sex of 

 the organism. Under normal conditions they are absent and 

 sex is then determined by 'Erbfaktoren' and 'Innenfaktoren.' 

 The latter he speaks of as female determining: ''Wenigstens 

 spielen mannchenbestimmende Innenfaktoren keine auffallige 

 Rolle." These factors are local conditions in the germ gland 

 which retard the migration of the germ cells into the sex cords. 

 The 'Erbfaktoren,' however, are supposed to be the chief sex 



