164 GERM-CELL CYCLE IN ANIMALS 
it united with one of the first eight cells. Further- 
more, it apparently always fused with a certain 
definite cleavage cell. The authors conclude that the 
Copulationszelle has some important relation to the 
history of the germ cells. 
The keimbahn of Cyclops and some closely allied 
forms has been very carefully investigated by Haecker 
Fic. 48.— Cyclops. A. Egg showing “ Aussenkérnchen”’ (ak) at one 
end of first cleavage spindle. B. Thirty-two-cell stage showing 
““Aussenkérnchen”’ (ak) in the primordial germ cell (Kz). Rk= 
polar bodies. (From Haecker, 1897.) 
(1897), Amma (1911), and Fuchs (1913) with results 
which are of particular interest. In Cyclops, accord- 
ing to Haecker, “‘Aussenkérnchen”’ arise at one pole 
of the first cleavage spindle (Fig. 48, A, ak); these 
are derived from disintegrated nucleolar material 
and are attracted to one pole of the spindle by a dis- 
similar influence of the centrosomes. During the 
first four cleavage divisions the granules are segregated 
always in one cell (Fig. 48, B, Kz); at the end of the 
fourth division these “‘Aussenkérnchen”’ disappear, 
but the cell which contained them can be traced by 
its delayed mitotic phase and is shown to be the 
primordial germ cell. 
