82 PETER OKKELBERG 



these potencies are practically in a balanced condition is seen 

 from the fact that both male and female sex cells appear in the 

 majority of larvae. Sometimes a larva is inclined more strongly 

 toward the female side and at other times it leans toward the 

 male side. In some cases it appears that a larva may fluctuate 

 back and forth between the two extremes until finally one or the 

 other sex condition takes the lead and sex reversal becomes more 

 difficult. This is indicated by the fact that the sex glands of 

 older larvae from the period of sex differentiation (larvae 50 mm. 

 to 70 mm. long) often show that an earlier sex condition has 

 been replaced by that of the opposite sex. After sex has become 

 definitely established, one or the other sex potency becomes so 

 strong that only unusual circumstances are able to reverse the 

 condition. The elements in the body or in the germ gland, which 

 have speciaUzed in the opposite direction, stop developing and 

 either degenerate or remain in an undeveloped condition during 

 the whole hfetime of the animal. The cysts in the developing 

 ovary contain small cells which soon degenerate and disappear 

 so that the larva soon becomes apparently a pure female. In 

 the developing male gland the undeveloped oocytes remain, in 

 many cases, even up to the adult stage ; but often they degenerate 

 in early stages, so that fragments of oocytes occur in the develop- 

 ing testes. Out of the juvenile hermaphroditic condition, there- 

 fore, both males and females eventually emerge. 



The condition in the lamprey is not essentially different from 

 that in Myxine, except that in the latter the two kinds of germ 

 cells develop in different parts of the gonad, while in the lamprey 

 there is no segregation of the two kinds of cells. The whole 

 gland is in fact hermaphroditic in the lamprey while in Myxine 

 the anterior portion of the gonad is ovarian and the posterior 

 portion testicular. In some individuals of Myxine there is a tend- 

 ency for the two kinds of cells to be mixed. This is especially 

 true on the border-line between the testicular and ovarian por- 

 tions. There is also probably no essential difference between the 

 condition in the frog and that in the lamprey, and an explanation 

 of the phenomena in one case should hold for the other as well. 

 Whether or not different races of lampreys show a greater or 



