GERM CELLS IN THE ARTHROPODA 171 
this nurse cell is confined to one cell (Fig. 50, C—E) 
which gives rise during the third cleavage (8- to 16- 
cell stage) to the primordial germ cell, containing 
the remains of the nurse cell (Fig. 50, E, K), and to 
the primordial entoderm cell which does not receive 
any part of the nurse cell (Fig. 50, E, e). The pri- 
mordial germ cell and primordial entoderm cell do not 
divide as quickly as the other blastomeres during 
the succeeding cleavage stages —a fact that aids 
in their identification. While the egg is undergoing 
cleavage the nurse cell is gradually changing, so that 
when the sixteen-cell stage is reached it has become 
disintegrated into dark staining granules and frag- 
ments of various forms and sizes (Fig. 50, EZ). Dur- 
ing the division of the “‘Keimbahnzelle” (from 16- 
32-cell stage) these granules and fragments are about 
equally distributed between the daughter cells (Fig. 
50, F). A similar distribution takes place in suc- 
ceeding divisions of the primordial germ cells, and 
this is accompanied by a further decrease in the size 
of the dark staining granules. A blastula of 236 
cells is figured by Kiihn which shows at the vegeta- 
tive pole four primordial germ cells lying next to 
eight entoderm cells and bordered by twelve meso- 
derm cells. During gastrulation this group of twenty- 
four cells becomes surrounded by the ectoderm cells, 
and the primordial germ cells may then be recognized 
as the anlage of the reproductive organs. 
Kiihn discusses the origin and significance of the 
*“Nahrzellenkern”’ and compares this body with 
similar bodies which have been found in the primor- 
