PRELIM IX A RY GENERAL SKETCH 



183 



E F 



Fig. 90. —Fertilization of the egg oi Ascaris megalocephala, van bivalens. [BOVERI.] (For 

 later stages see Figs. 31, 145.) 



A. The spermatozoon has entered the egg, its nucleus is shown at d" ; beside it lies the granu- 

 lar mass of " archoplasm " (attraction-sphere) ; above are the closing phases in the formation 

 of the second polar body (two chromosomes in each nucleus). B. Germ-nuclei ( ? , J) m the 

 reticular stage; the attraction-sphere (a) contains the dividing centrosome. C. Chromosomes 

 forming in the germ-nuclei ; the centrosome divided. D. Each germ-nucleus resolved into two 

 chromosomes; attraction-sphere («) double. E. Mitotic figure forming for the first cleavage; 

 the chromosomes {c) already split. F. First cleavage in progress, showing divergence of the 

 daughter-chromosomes toward the spindle-poles (only three chromosomes shown). 



