236 GERM-CELL CYCLE IN ANIMALS 
an insect has a similar occurrence been noted, namely, 
in Polyphemus, where, according to Kiihn (1911, 
1913), the keimbahn-determinants consist of the 
remains of one or more nurse cells (Fig. 50). In the 
DapHnip& (Weismann and Ischikawa, 1889) the 
““Paracopulationszelle”’ arises from material cast out 
by the germinal vesicle; in 4/quora (Haecker, 1892) 
the “‘Metanucleolus”’ is likewise derived from the 
germinal vesicle; in Ascaris (Boveri, 1892) chroma- 
tin-diminution occurs during the two- to four-cell 
stage; in Cyclops (Haecker, 1897, 1903) and other 
copepods (Amma, 1911) the ‘“Aussenkérnchen”’ or 
““Ectosomen” become visible soon after fertiliza- 
tion (Diaptomus), but usually not until the pro- 
nuclei fuse (other species); in Sagitta the “be- 
sondere Kérper” (Elpatiewsky, 1909, 1910) or 
“Keimbahnchromidien”’ (Buchner, 1910) appear to 
arise de novo after fertilization, although if Buchner’s 
contention that they are the remains of the accessory 
fertilization cells is correct, they should be classed 
with the ‘“Nahrzellenkern” described by Kiihn 
(1911, 1913) in Polyphemus. 
It is thus evident that the keimbahn-determinants 
become visible, wherever they have been described, 
either just before or just after the eggs are fertilized, 
or, in parthenogenetic forms, shortly before matura- 
tion and cleavage are inaugurated. 
The localization of the keimbahn-determinants at 
the time of their appearance seems to be predeter- 
mined. In insects the posterior end of the egg is 
invariably the place where these bodies occur. In 
