122 GERM-CELL CYCLE IN ANIMALS 
fifteen nurse cells lacking this nuclear substance. 
Thus as Paulcke’s theory demands, the difference 
between the nurse cells and the odcytes is the result 
of internal and not external causes. 
Giardina considered the formation of the chromatic 
ring as a sort of synapsis, and later (1902) distin- 
guished between a complete synapsis, such as 
ordinarily occurs in the germ-cell cycle, and a partial 
synapsis as exhibited by Dytiscus. Regarding the 
significance of this differential mitosis, he maintains 
that this phenomenon is the cause of the differen- 
tiation into nurse cells and odcytes, resulting in a 
complete amount of chromatin in the keimbahn 
cells and perhaps also an unequal distribution of cyto- 
plasmic substances. As in the case of Ascaris and 
Miastor, it might better be regarded as a means of 
depriving the nurse cells of part of their chromatin. 
Moreover, Boveri (1904) has compared the chroma- 
tin-diminution in Ascaris with Giardina’s differ- 
ential mitoses. Debaisieux (1909) and Giinthert 
(1910) have confirmed Giardina’s results, and the 
latter studied two other Dytiscipm, Actlius and 
Colymbetes, which also exhibit differential mitoses 
similar except in certain details. Giinthert found 
that the chromatic ring is composed of fine granules 
which may split off from the surface of the chromo- 
somes (compare with Ascaris and Miastor) and stain 
like cytoplasm. He interprets this as ‘‘ Zerfallspro- 
dukte” of the chromosomes. Debaisieux, on the 
other hand, claims that this cast-out nuclear material 
is nucleolar rather than chromatic in nature. 
