482 ROBEET W. HEGNER 



daughter cells of the primordial germ cells (fig. 22) and both 

 Elpatiewsky ('09, '10) and Stevens ('10), therefore, consider 

 this as probably a differential division whereby in this hermaph- 

 roditic animal the substance of the male primordial germ cell 

 is separated from that of the female. More work is necessary 

 to make certain of this point. 



Conclusion. Keimbahn-determinants are definitely localized 

 in the egg and in definite cleavage cells. This localization is 

 first observable just before or just after the eggs are 'fertilized, 

 or, in parthenogenetic forms, shortly before maturation and 

 cleavage are inaugurated. Some mechanism in the egg must be 

 responsible for this localization. Heterodynamic centrosomes 

 may have some influence so far as the segregation of the Keim- 

 bahn-determinants in cleavage cells is concerned, but the move- 

 ment of the egg contents seems to be a more probable cause of 

 localization. 



C. The fate of the Keimbahn-determinants 



It is unfortunately impossible to trace tho Keimbahn-determi- 

 nants throughout the entire germ cell cycle. The question of 

 their fate, however, is an important one. As we have seen, they 

 become apparent shortly before or just after the inauguration 

 of the maturation divisions, and remain intact for a brief period 

 during the early cleavage stages. They persist in insects as def- 

 initely recognizable granules (fig. 8, F) for some time after the 

 primordial germ cells are segregated ; then they gradually break 

 up into finer particles, leaving no trace of their existence behind 

 except in so far as they give the cytoplasm of the germ cells a 

 greater affinity for certain dyes. In Chironomus they may 

 still form distinct masses after the definitive germ glands have 

 been formed (fig. 1). The ectosomes in the copepods are tem- 

 porary bodies which appear to rise de novo during the formation 

 of each mitotic figure in the early cleavage stages; then break 

 dowai and disappear. Practically all of the other Keimbahn- 

 determinants persist during early cleavage and then disappear 

 as distinct visible bodies as soon as the primordial germ cells 



