218 GERM-CELL CYCLE IN ANIMALS 



The elimination of chromatin during the matura- 

 tion and early cleavage divisions of the egg, as well 

 as during the mitotic divisions of other kinds of cells, 

 has often been recorded. For example, Wilson 

 (1895, p. 458) estimates that only about one-tenth 

 of the chromatin in the germinal vesicle of the star- 

 fish is retained to form the chromosomes during the 

 first maturation division, and Conklin (1902) finds 

 that "in Crepidula the outflow of nuclear material 

 occurs at each and every mitosis" (p. 51). Further- 

 more, Rhode (1911) argues that chromatin-diminu- 

 tion is a normal histological process, and describes 

 such phenomena in blood cells, nerve cells, and 

 cleavage cells of several Amphibia, comparing con- 

 ditions with the chromatin-diminution in Ascaris 

 and Dysticus} 



Diminution processes similar to those in Ascaris 

 and Miastor have not been discovered in other ani- 

 mals, although investigators have been on the watch 

 for such phenomena and have studied allied species, 

 e.g., the work of Hasper (1911) on Chironomus and 

 my own work on the chrysomelid beetles (see pp. 108 



* His conclusion is as follows : " In der Histogenese der allerver- 

 schiedensten Gewebe tritt uns also die Erscheinung entgegen, dass 

 die sich entwickelnden Zellen, bzw. Kerne einen Teil ihres Chromatins 

 abstossen, d. h. also cine Chromatindiminution erfolgt, wenn auch 

 die Befunde selbst im speziellen von den bisher beobachteten in der 

 Einleitung beschriebenen Fallen der Chromatindiminution etwas ab- 

 weichen. 



"Eine Chromatindiminution tritt also nicht nur am Anfang und Ende 

 der Keimbahn, wie es bisher angegeben worden ist, sondem in den ver- 

 schiedensten Entwicklungsstadien und bei den verschiedensten Geweben 

 und Tieren ein, sie hat also oflfenbar eine allgemeine Bedeutung." (p. 25.) 



