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. 
Tue DIFFERENTIATION OF THE NUCLEI OF THE 
BLASTODERM CELLS, PRIMORDIAL GERM CELLS, AND 
ViteLLopHacs. 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, 1909), 
1911a), 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-dise. (2) The nuclei 
of the blastoderm cells are small and completely 
filled with large spherical chromatin granules. 
