IV. i INITIAL STRUCTURE OF THE GERM 231 



FIG. 142. Normal development of the egg of Cynthia partita. Matura- 

 tion and fertilization. (After Conklin.) 



A. Unfertilized egg before the fading of the germinal vesicle (clear), 

 showing central mass of grey yolk (lightly dotted), peripheral layer of 

 yellow protoplasm (thickly dotted), test-cells and chorion. 



B. After the entrance of the spermatozoon the yellow protoplasm has 

 streamed to the vegetative pole (c) ; in it, excentrically, is the sperm 

 nucleus (sp.n). The clear protoplasm derived from, the germinal vesicle 

 partly forms a layer over the yellow protoplasm, in part remains at the 

 animal pole (). The grey yolk occupies the animal part of the egg. 



c. The yellow and clear protoplasmic substances have both streamed 

 to what will be the posterior side (P). A, anterior, V, ventral (animal 

 pole), D, dorsal (vegetative pole). 



D. View of the same egg from behind. The two pronuclei are seen 

 side by side in the clear area. B, right ; L, left. 



