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 to unite 

 with it. The 



FIG. 15. Miastor metraloas. Three of the four cleavage di- 

 division figures (I, III, IV) of the four- to eight- , i 



cell stage represented. cMp = chromosome V1S1 

 middle plate ; n.c = nurse chamber ; p.b = polar place bv mi- 

 body; pPl = pole-plasm. (From Kahle, 1908.) * 



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. 



pp.l 



