466 ROBERT W. HEGNER 



Kerne einen Tell ihres Chromatins abstossen, d.h. also eine Chromatin- 

 diminution erfolgt, wenn audi die Befunde selbst im speziellen von den 

 bisher beobachteten in der Einleitung beschriebenen Fallen der Chro- 

 matindiminution etwas abweichen. 



Eine Chromatindiminution tritt also nicht nur am Anfang und 

 Ende der Keimbahn, wie es bisher angegeben worden ist, sondern in 

 den verschiedensten Entwicklungsstadien und bei den verschiedensten 

 Geweben und Tieren ein, sie hat also offenbar eine allgemeine Bedeu- 

 tung (pp. 24-25). 



Diminution processes similar to those in Ascaris and Miastor 

 have not been discovered in other animals, although investi- 

 gators have been on the watch for such phenomena and have 

 studied allied species, e.g., the work of Hasper ('11) on Chirono- 

 mus and my own work on the Chrysomelid beetles (pp. 410 to 

 411). If, therefore, there be a similar difference in chromatin 

 content between the germ cells and somatic cells in all animals, 

 the elimination of chromatin from the latter must take place by 

 the transformation of the basichromatin of the chromosomes 

 into oxychromatin which passes into the cytoplasm during 

 mitosis, or else by the more direct method advocated by the 

 believers in the chromidia hypothesis. 



The causes of the diminution of chromatin in Ascaris and 

 Miastor are unknown. Recently Boveri ('10) has concluded from' 

 certain experiments on the eggs of Ascaris (p. 444) that in this 

 form it is the cytoplasm in which the nuclei are imbedded which 

 determines whether or not the latter shall undergo this process. 

 Kahle ('08) does not explain the cause of the diminution in Mias- 

 tor. To the writer it seems more important to discover why 

 the nuclei of the Keimbahn cells do not lose part of their chromatin, 

 since the elimination of chromatin during mitosis is apparently 

 such a universal phenomenon. I would attribute this failure of 

 certain cells to undergo the diminution process, not to the con- 

 tents of the nucleus alone, but to the reaction between the 

 nucleus and the surrounding cytoplasm. As stated in a former 

 paper (Hegner, '09) : 



In Calligrapha all the nuclei of the egg are apparently alike, potenti- 

 ally, until in their migration toward the surface they reach the 'Keim- 

 hautblastem;' then those which chance to encounter the granules of 



