EXPLAXATIOX OF PLATES 



The essential features of all figures were drawn with a camera lucida. Unless 

 otherwise stated, the magnification is 1000 diameters. 



PLATE 1 



EXPLAXATIOX OF FIGURES 



1 F 9 X C cf ; aster divided; germ-nuclei not yet closely apposed. 



2 F 9 X F c? ; germ-nuclei about to fuse; aster undivided. 



3 F 9 X F cf ; segmentation nucleus. 



4 and 5 F 9 X C cf; germ -nuclei closely apposed but not fused. 



6 F 9 X C cf ; prophase of first cleavage; the nuclei have not fused. 



7 F 9 X F cf ; prophase of first cleavage; the nuclei have fused. 



8 F 9 X C cf; early anaphase, first cleavage; paternal and maternai chro- 

 matin mingled (X 2500). 



9 C 9 X C cf ; metaphase, first cleavage. 



10 F 9 X F cf; metaphase, first cleavage (X 2500). 



11 F 9 X C cf; early anaphase, first cleavage; paternal chromosomes grouped 

 on one side of the spindle. 



512 



