PLATE 17 



EXPLANATION OF FIGURES 



75 Section through the otocysts of the embryo of which figures 62, 63 and 

 64 are sections. The precardinal lines are indicated by erythrocytes. There 

 are erythrocytes in the very rudimentary short ventral aorta. 



76 Section through the optic region of an embryo of Erimyzon sucetta ob- 

 longus. Embryo at cell stage was treated with a weak solution of KCN. Dorsal 

 to each eye are erythrocytes in all stages of development. — Kindness of Pro- 

 fessor McClure. 



ABBREVIATIONS 



Erthbl., erythroblast Erth., erythrocyte 



164 



