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-dise 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, 1911a). 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-dise 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 
