The Cellular Basis 



137 



FIG. 43. FERTILIZATION OF THE EGG OF THE NEMATODE WORM Ascaris 

 megalocephala. 9 N, Egg nucleus. $ N, Sperm nucleus. Arch, Archiplasm. 

 C, Centrosome. A, B, Approach of germ nuclei. C, D, Formation of two 

 chromosomes in each germ nucleus. E. F } Stages in the division of the 

 chromosomes which are split in E and are separating in F; only three 

 of the four chromosome pairs are shown in F. (From Wilson after 

 Boveri.) 



