KEIMBAHN-DETERMINANTS 225 
lies, is cut off as a cell which gives rise to the pole- 
cells. 
In certain Dapunipm, Weismann and Ischikawa 
(1889) describe a “Paracopulationszelle’’ which is 
derived from the contents of the germinal vesicle 
(see p. 163) ; but the recent work of Kiihn (1911, 1913) 
renders it probable that this body is nothing but 
the remains of a nurse cell. The “Dotterplatte” 
discovered by Noack (1901) at the posterior end of 
the egg of Calliphora (Fig. 34) is considered by this 
investigator to consist of yolk elements. In previous 
communications (Hegner, 1908, 1909, 1911) the 
writer has discussed the probability that the pole-disc 
in chrysomelid eggs consists of nutritive material, 
and Weiman (1910a) also has offered arguments 
for this view. 
The granules segregated in certain cleavage cells of 
Nertina (Blochmann, 1881), Asplanchna (Jennings, 
1896), Lepas (Bigelow, 1902), Siphonaria (Fujita, 
1904), and Physa (Wierzejski, 1906) may be of a 
nutritive nature, and these cells may be the stem 
cells from which the germ cells of these animals 
eventually arise. The hypothesis that the nucleoli 
consist of food substance also argues in favor of the 
idea that the keimbahn-determinants are nutritive. 
The importance of these nutritive substances 
to the primordial germ cells can be stated with some 
degree of certainty. According to some authorities 
the primordial germ cells remain in the primitive 
condition and do not undergo differentiation at the 
same time, or at least at the same rate, as do the 
Q 
