56 GERM-CELL CYCLE IN ANIMALS 
disintegrate and disappear, apparently without 
performing any function. As in most other animals, 
these polar bodies may be considered abortive eggs. 
The female pronucleus moves into the central an- 
terior part of 
the egg where 
it becomes em- 
bedded in the 
cytoplasmic 
mass near the 
nurse chamber. 
It may now be 
designated as 
the cleavage 
nucleus, since 
the eggs of 
Miastor develop 
without  ferti- 
lization and 
hence no male 
pronucleus is 
present tounite 
with it. The 
Fic. 15.— Miastor metraloas. Three of the four cleavage di- 
division figures (I, III, IV) of the four- to eight- _+ + tak 
cell stage represented. cMp = chromosome visions ake 
middle plate; n.c = nurse chamber; p.b= polar place b mi- 
body; pPl=pole-plasm. (From Kahle, 1908.) P 7 y 
tosis, and, as 
in most of the ARTHROPODA, the early cleavage nuclei 
are not separated by cell walls, but simply move 
apart after each successive division. The egg during 
this period is thus a syncytium within which the 
limits of the cells are difficult to define. 
