220 GERM-CELL CYCLE IN ANIMALS 
not a cell will become a germ cell depends on its posi- 
tion in the egg just previous to the formation of the 
blastoderm.” 
Similarly in Ascaris the cleavage nuclei are con- 
ceived as similar so far as their “prospective potency” 
is concerned, their future depending upon the char- 
acter of their environment, 7.e., the cytoplasm. In 
the egg of Miastor cleavage nucleus IV (Fig. 15) does 
not lose part of its chromatin because of the character 
of the reaction between it and the substance of the 
““polares Plasma.” In chrysomelid beetles (Hegner, 
1908, 1909, 1914a) and Chironomus (Hasper, 1911), 
however, although no diminution process has been 
discovered in the nuclei that encounter the pole-disc 
or “Keimbahnplasma,” the other nuclei in the egg, 
so far as known, are similar in this respect. The 
nuclei of the primordial germ cells, however, may be 
distinguished easily from those of the blastoderm 
cells in chrysomelid beetles, proving conclusively 
that a differentiation has taken place either in one 
or the other. This differentiation probably occurs in 
the nuclei that take part in the formation of the 
blastoderm, since the nuclei of the germ cells retain 
more nearly the characteristic features of the pre- 
blastodermic nuclei, whereas those of the blastoderm 
cells change considerably. 
In some cases the eliminated chromatin may have 
some influence upon the histological differentia- 
tion of the cell, since it is differentially distributed 
to the daughter cells, but in Ascaris and Miastor 
no mechanism exists for regulating the distribution 
