GERM-CELL HISTORY IN THE BROOK LAMPREY 91 



simply initiates development in the egg and the sperm nucleus 

 degenerates. The parthenogenetically developing egg forms a 

 hermaphrodite. Only in one case was a fusion of the male 

 and the female nucleus observed, and Miss Krliger assumed that 

 the male nucleus in this case was one in which the accessory chro- 

 mosome was lacking. This would give rise to a male of which 

 there were a few formed. 



Demoll ('12) thinks that in Helix pomatia, which is hermaphro- 

 ditic, two kinds of spermatozoa result from the unequal distri- 

 bution of the sex chromosome and that only one kind, that with 

 the accessory, becomes functional. 



It appears from the above cases, namely, that of the gastro- 

 pods, which are true hermaphrodites, and that of Rhabdites, in 

 which the hermaphroditic condition alternates with the dioe- 

 cious, that sex cannot be the result of the action of the sex chro- 

 mosome alone, but that the activities and behavior of the sex 

 chromosomes which results in their peculiar distribution must be 

 due to some physiological activity in the cell which antedates 

 the sex chromosomes, so that the latter are simply the final link 

 in a series of processes which determine the sex potentiality of 

 the cell. This possibility has been admitted by Schleip in the 

 case of Rhabdites. He says: ''Es scheint, dass die Entwick- 

 lung mancher Keimzellen zu Spermatozyten statt zu Ovozyten 

 zum Teil auf Ursachen beruht, die ausserhalb dieser Keimzellen 

 liegen." . . . ''Diese ausseren Ursachen brauchen nicht 

 ausserhalb desselben befinden; man kann sogar vielleicht daran 

 denken, dass innere Secretion dabei eine Rolle spielt" (p. 128). 

 Further on Schleip adds that external conditions may influence 

 the development of the sex cells. He says: ''Wie bei manchen 

 Tieren aussere Bedingungen einen Einfluss auf das Geschlecht der 

 sich entwickelnden Tiere auszuiiben imstande zu sein schienen, so 

 beeinflussen also aussere Bedingungen bei der zwittrigen Genera- 

 tionen die Entwicklungsrichtung der Keimzellen." He says 

 further: "Daher wird die Frage erlaubt sein, ob die verschiedene 

 Chromosomenzahl iiberhaubt einen Einfluss auf die Gesch- 

 lechtsbestimmung hat, und ob die Spermien nicht aus anderen 

 Ursachen und in anderer Weise in mannliche und weibliche dif- 



