24O \V. M. SMALLWOOD. 



EXPLANATION OF J'l.A'l E IV. 



FK; 21. Shows the presence of several nuclei in the unsegmented egg, one of 

 which is probably the female pronucleus, pronl. 9- 



FIGS. 22 to 24. Three forms of the pVophase in cleavage. Pig. 22, conjugation 

 of pronuclei and formation of first segmentation spindle. In Fig. 23 the chromosome 

 vesicles have not united. Pronl. 9 female pronucleus ; pronl. J 1 , male pronucleus ; 

 vsl. (hr'so, chromosome vesicles ; c'sp, centrosphere. 



FIGS. 25, 26, 27. Show the appearance of the segmentation spindle, migration of 

 the chromosomes, and presence of the centrosphere ; r'j/>, centrosphere. 

 FIG. 28. Inclusions in the cytoplasm. 



