30 



CHARLES R. STOCKARD 



Fig. 21 Caudal end of an embryo of ninety-six hours, without a circulation; 

 Kv, the distended Kupffer's vesicle with pigment cells collected around it. Bi, 

 yolk-sac blood islands on the posterior yolk region. 



Fig. 22 Lateral view of eight-day embryo, without a circulation, showing 

 red blood corpuscles in the stem vein, .ST, and also masses of blood islands, 

 Bi, on the ])osterior ventral yolk regions. 



Figs. 23 and 2-t Posterior veiws of two seventy-two hour embryos, without 

 blood circulation. Cells are seen wandering out from the tail, T, region into the 

 position of the peripheral mesoderm in most meroblastic eggs; these cells collect 

 into groups and form the blood isUmds, Bi. 



