2O4 J- THOMAS PATTERSON. 



PLATE VI. 



FIG. 21. An ovum shortly before the formation of the first polar body. The 

 nucleus is the product of the fusion of the chromosome-vesicles of a stage like that 

 in Fig. 19. The section passes through but one of the two ova in the capsule. In 

 most of the capsules of this period the protoplasm of the eggs contracts in the re- 

 agents more than does the surrounding vitelline material, thus producing a clear 

 space between the two materials. X 543. 



FIG. 22. A capsule in which both eggs are undergoing maturation at the same 

 time. X 543- 



FIG. 23. Two of the tetrads from the preceding figure. X 2,394. 



FIG. 24. The cutting off of the first polar body. This egg is a mate to the one 

 shown in Fig. 20. X 798. 



FIG. 25. This stage shows the close of maturation. The first polar body has 

 undergone division and is disintegrating. X 543. 



FIG. 26. Fertilization stage. X 543. 



