GERM-CELL HISTORY IN THE BROOK LAMPREY 117 



part in the formation of somatic structures. Numerous germ 

 cells are produced which do not become functional, and these 

 degenerate and disappear during the process of development. 



3. The germ cells of each germ gland are usually of two kinds 

 namely, those showing a tendency toward rapid division (kata- 

 bolic) and those showing a tendency for growth (anabolic). The 

 former are regarded as having a male, the latter a female poten- 

 tiality. The relative proportion of anabolic and katabolic cells 

 determines whether the larva becomes a male or a female indi- 

 vidual. 



4. Observations seem to warrant the conclusion that each 

 larva of this species carries the potentiality of both sexes, and 

 that sex, therefore, is not irrevocably fixed at fertilization. 



