GERM CELLS IN THE ARTHROPODA 141 



chrysomelid eggs both germ cells and somatic cells 

 possess the full amount of chromatin or else the 

 elimination of this substance takes place in some 

 other way. 



THE DIFFERENTIATION OF THE NUCLEI OF THE 

 BLASTODERM CELLS, PRIMORDIAL GERM CELLS, AND 

 VITELLOPHAGS. The conclusion that no chromatin- 

 diminution process occurs during the early cleav- 

 age divisions in the eggs of chrysomelid beetles 

 necessitates the search for some other method of 

 differentiation among the cleavage nuclei. The 

 insect egg is particularly advantageous for testing 

 Roux's hypothesis of qualitative nuclear division, 

 since we have here the production of an enormous 

 number of nuclei before any cell walls are formed, 

 and an egg that is remarkably definitely organized, 

 as indicated by my experiments (Hegner, 19096, 

 191 la), before the blastoderm is formed. 



I have been unable to find any differences in the 

 nuclei before they fuse with the keimhautblastem, 

 but as soon as this does occur, a gradual change takes 

 place, and at the time when the blastoderm is com- 

 pleted three sorts of nuclei are distinguishable: 

 (1) The nuclei of the primordial germ cells (Fig. 36, 

 C) are larger than the others and contain compara- 

 tively few spherical chromatin granules evenly dis- 

 tributed. The cytoplasm of these cells is distin- 

 guishable from that of all other cells because of the 

 presence of granules from pole-disc. (2) The nuclei 

 of the blastoderm cells are small and completely 

 filled with large spherical chromatin granules. 



