KEIMBAHN-DETERMINANTS 229 



dence of this underlying organization. As I have 

 stated elsewhere (Hegner, 1908, p. 21) regarding the 

 keimbahn-determinants in beetles' eggs, "the 

 granules of the pole-disc are therefore either the germ- 

 cell determinants or the visible sign of the germ-cell 

 determinants." The writer's experiments have thus 

 far failed to determine the exact function of these 

 granules. When the posterior end of a freshly laid 

 beetle's egg is pricked with a needle, not only the 

 pole-disc granules flow out, but also the cytoplasm 

 in which they are embedded (Hegner, 1908). If a 

 small region at the posterior end is killed with a hot 

 needle, the pole-disc is prevented from taking part 

 in the development of the egg, but so also is the sur- 

 rounding cytoplasm (Fig. 37, c). Eggs thus treated 

 continue to develop and produce embryos without 

 germ cells, but as a rule a part of the posterior end 

 of the abdomen is also absent (Hegner, 191 la). The 

 pole-disc granules and the cytoplasm containing 

 them is moved by centrifugal force toward the heavy 

 end of the egg and is proved to be quite rigid, but 

 eggs thus treated do not develop sufficiently normally 

 to enable one to decide whether the pole-disc pro- 

 duces germ cells in its new environment or not. 



That the germ cells of Chironomus arise from a pre- 

 localized substance was stated by Balbiani (1885) in 

 these words, "the genital glands of the two sexes 

 have an absolutely identical origin, arising from 

 the same substance and at the same region of 

 the egg." Ritter (1890) expressed the opinion 

 that the "Keimwulst" of Chironomus consists of fine 



