GERM CELLS IN THE ARTHROPODA 109 
at the four cell stage becomes separated from the 
rest of the egg, together with all of the Keimbahn- 
plasma as the primordial germ cell (Fig. 33 B, 
p.g.c.). The Keimbahnplasma is apparently equally 
divided between the daughter cells when the 
primordial germ cell divides. Later the nuclei 
of the germ cells increase in number without an 
accompanying division of the cell, thus producing 
binucleated cells (Fig. 33, C). The history of the 
pole cells during embryonic development will be 
more fully described in the CoLEOPTERA, since in 
the beetles the Keimbahn is much more distinct. 
The origin and nature of the Keimbahnplasma 
was not determined by Hasper, but it was found to 
persist in certain cases even until the larval stage 
was reached (Fig. 33, D). 
In Calliphora Noack (1901) described a dark 
granular disc at the posterior end of the egg (Fig. 34) 
which he termed the ‘‘Dotterplatte’ and which, 
like the pole-plasm of Wiastor and the Keimbahn- 
plasma of Chironomus takes part in the formation of 
the primordial germ cells. The eggs of the parasitic 
fly, Compstlura concinnata, were also found by the 
writer (Hegner, 1914a) to possess a granular pole- 
disc, thus adding one more species to the list of 
Diptera in which such a structure exists. 
CoteoPrerA. The origin of the germ cells in 
beetles and their subsequent history are well known 
only in certain species of the family CHRYSOMELID 
of the genera Calligrapha and Leptinotarsa. The 
contributions of Wheeler (1889), Lecaillon (1898), 
