Plate I. 



Fig. 1. — Mature egg in living state, in natural color?, x 310. pi. bd.= 



polar body. 

 Fig. 2.— 2-cell stage, from life, x 310. 

 Fig. 3.— 3-cell stage, from life, x 310. 

 Fig. 4. — 4-cell stage, from life, x 310. 

 Fig. 5. — 8- cell stage, from life, x 310. 



Fig. 6. — Late 8-cell stage, from a preserved specimen, x 380. 

 Fig. 7. — Same egg as Fig. 6, in side view, x 380. 

 Fig. 8.— 16-cell stage, from life, x 310. 

 Fig. 9— 32-cell stage, from life, x 310. 

 Fig. 10.— Blastula, from life, x 310. 



Fig. 11.— Blastula slightly compressed, in optical section, from life, x 310. 

 Fig. 12. — Blastula, in which the gastrula invagination has commenced, 



slightly compressed, in optical section, from life, x 310. 

 Fig. 13. — Dwarf gastrula developed from a blastomere of the 2-cell stage, 



in optical section, x 370. 



