GERM-CELL HISTORY IN THE BROOK LAMPREY 75 



Teleostei. Certain species of teleosts belonging to the families 

 Sparidae and Serranidae are said to be normally hermaphroditic, 

 and those of the latter family are even said to be self-fertilizing 

 (Brock, '81; Howes, '91). Brock found in certain species of 

 Sparidae that some of the young were hermaphroditic and others 

 unisexual. In the former the ovarian elements did not mature 

 and they became males, while the latter became females. I have 

 shown that in the young lamprey the male part of the predomi- 

 nantly female gonad soon disappears, or is at least in many cases 

 not very conspicuous, so that the impression may be gained by 

 superficial examination of certain individuals that they are pure 

 females. In the male, however, the female character, namely, 

 the presence of oocytes, persists in many cases even up to the 

 adult stage. For this reason one might conclude from the 

 examination of older larvae that the males alone are hermaphro- 

 ditic or heterozygotic as to sex. This was the conclusion that I 

 first reported ('14). From a more careful examination of earlier 

 stages I have now found that there is essentially no difference 

 between the males and the females with regard to the juvenile 

 hermaphroditic condition and that the apparent purity of the 

 older larval females is due to the fact that the male character in 

 the form of cell nests does not persist for any length of time after 

 the female character has become predominant. Out of the her- 

 maphroditic larvae, therefore, both males and females develop, 

 and not males only as was at first supposed. In bony fishes 

 there are no recent researches on sex differentiation, and the 

 problem of juvenile hermaphroditism in this group needs to be 

 reinvestigated. It may be expected to occur in both sexes. 



Amphibia. It has long been known that in toads anterior to 

 the true sex gland there is an organ (Bidder's organ) which has the 

 structure of a rudimentary ovary. In males it persists through- 

 out life, but in females it disappears after the second year in all 

 forms that have been studied with the exception of Bufo vulgaris, 

 in which, according to Ognew ('06), it is retained throughout life. 

 Certain cells in this organ are, in structure and development 

 similar to true oocytes. Ognew states that the boundary between 

 Bidder's organ and the germ gland is often quite indefinite, so 



