INTRODUCTORY 



name of Karyokinesis. The accompanying figures will show 



how entangled the process is. There is no need, however, 



to follow it out in detail, but only to emphasise one or two 



points. First, the important part 



is not played, it is believed; by 



the small star-like body called the 



astrosphere which appears near the 



nucleus, but by the nucleus itself 



and not by the whole of it, but 



by certain loops of protoplasm 



which it contains and which take up 



colour very readily, for which reason 



they are called the chromosomes. 



In the course of the process each FlG 2 ._ Diagram iii ustrating thc matu . 



loop Splits along itS entire length, ration of the ovum. The first polar 



. \ r r T- i globule is forming. Mem, egg 



SO that the fOUr m fig, B have membrane; pol, polar body; cent, 



become eight in fig. C. Under centrosome. (From Parker and 



Has well's Zoology. ,) 



ordinary circumstances at the end 



of the nuclear division there would be two cells, but in 



the case of the egg, this is not so: one of the resulting 



FIG. 3. Various stages in the segmentation or the ovum. 

 (From Parker and Haswell after Gegenbaur). 



halves of the nucleus shrivels into a round particle, called 

 the polar body, and is ejected (fig. 2). The process of division 



