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GENERAL EMBRYOLOGY 



FIG. 94. Fertilization in Ascaris megalocephala bivalens. From Wilson, 

 "Cell," after Boveri. (Later stages are shown in Fig. 36.) A. The spermato- 

 zoon has entered the egg, its nucleus is shown at cT; beside it lies the granular 

 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 (9 , d" 1 ) in the reticular stage; the attraction-sphere (a) contains the 

 dividing centrosome. C. Chromosomes forming in the germ-nuclei; the centro- 

 some divided. D. Each germ-nucleus resolved into two chromosomes; attrac- 

 tion-sphere (a) 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) . 



