GERM-CELL HISTORY IN THE BROOK LAMPREY 107 



the other, may be considered homologous characters of the oppo- 

 site sexes. 



Judging from the quantitative appearance of the characters 

 in the germ glands of hundreds of larvae which have been care- 

 fully studied, the conclusion is reached that every individual is a 

 potential hermaphrodite possessing the sex qualities pertaining 

 to either sex. It appears, however, that some individuals are 

 more strongly inclined toward the male side, others more strongly 

 toward the female side. Some, on the other hand, are appar- 

 ently in a balanced condition as regards sex, and it would be im- 

 possible to say whether they are more strongly male or more 

 strongly female. This condition usually lasts only a short time, 

 after which one sex takes the lead over the other. When, in the 

 course of time, an individual has become more strongly male or 

 female, the opposite sex character gradually disappears, or at 

 least remains undeveloped; so that if it appear at all in the adult, 

 it is in a rudimentary or degenerate condition. This is the case, 

 for instance, with the oocytes which are in an undeveloped condi- 

 tion in the adult testes. The secondary sex characters which 

 appear in the adult are probably not hereditary characters at all, 

 but are formed as a result of the presence of special kinds of 

 hormones produced by the testis or ovary. These secondary 

 characters are not present until after metamorphosis, when one 

 or the other appears, depending upon the form of germ gland 

 present. 



As far as the primary sex characters are concerned, it appears 

 that both male and female potencies exist in every individual 

 from the beginning of development; that is, from the time that 

 the egg is fertilized, and probably in both of the sex cells that 

 are brought together in fertilization. These potencies then are 

 transmitted from parents to offspring. It seems quite likely, 

 however, that the two potencies are not always transferred from 

 parent to offspring in equal strength, so that the two are not, in 

 all cases, in a balanced condition from the very beginning. This 

 appears from the fact that during the stage of sex differentiation 

 all kinds of variations are found as to the quantitative appearance 

 of the male and female characters. Since all of the larvae develop 



