KEIMBAHN-DETERMINANTS 235 
B. Tue Locauization oF THE KEIMBAHN-DETER- 
MINANTS 
One of the characteristics of the keimbahn- 
determinants is their regular appearance at a certain 
stage in the germ-cell cycle according to the species in 
which they occur, and their constant localization 
in a definite part of the egg, or in one or more definite 
cleavage cells. Keimbahn-determinants are recog- 
nizable in many insects’ eggs before fertilization is 
accomplished, and even before the odcyte has reached 
its maximum size. We know that in Chironomus 
the ‘“Keimwulst” (Ritter, 1890) or “‘Keimbahn- 
plasma’”’ (Hasper, 1911) is present when the egg 
is laid, at which time the pronuclei as a rule have 
not yet fused. This is true also of the “Dotter- 
platte” in Calliphora (Noack, 1901). There can 
be little doubt, however, that these substances 
are present as such in the eggs before fertilization, 
judging from our knowledge of the history of similar 
materials in the eggs of other insects. The “‘pole- 
disc” in the eggs of chrysomelid beetles (Hegner, 
1908; Wieman, 1910a) and the “‘polares Plasma” 
in Miastor (Kahle, 1908; Hegner, 1912, 1914a) are 
recognizable some time before fertilization and cannot 
therefore arise because of any influence exerted by 
the spermatozoén. Moreover, in Miastor the eggs 
thus far examined have all been parthenogenetic. 
In parasitic Hymenoptera the Keimbahn-chromatin 
appears in both fertilized and parthenogenetic eggs 
at an early growth period. In only one animal not 
