The yolk mass is novr oval-shaped j the fin-fold is wide, bein,^ 1 1/2 

 to 2 times as wide as the body; the tail is divided into somites 

 to its very tip, which is now somewhat pointed. The eyes are still 

 colorless, pigmentation taking place after hatchin;j. This stage 

 ends with the hatching of the egg. 



KEY to Plates 



Plate 1 



Stage I 



Stage II, fairly early 



Stage II, late 



Stage III, intermediate, dorsal view 



Stage IV, beginning 



Stage V, beginning 



Stage V, imiite iiately be'fore closing of 



blastopore, ventral view 

 Stage VI, early 

 Stage VI, late 



Plate 2 



151 



