The Cellular Basis 



139 



grow in size by the absorption of achromatin from the cell body 

 forming the chromosomal vesicles in which the chromatin takes 

 the form of threads and granules, the chromosomal vesicles unite 

 to form the daughter nuclei and these nuclei come back to a "rest- 



9 * * 



H 



FIG. 44. MATURATION AND FERTILIZATION OF THE EGG OF THE MOUSE. 

 A, First polar body and second maturation spindle. B, second polar body 

 and maturation spindle. C, Entrance of the spermatozoon into the egg. 

 D-G, Successive stages in the approach of egg and sperm nuclei. H, for- 

 mation of chromosomes in each germ nucleus. /, First cleavage spindle 

 showing chromosomes from egg and sperm on opposite sides of spindle. 

 (After Sobotta.) 



