30 



CHARLES R. STOCKARD 



SV 



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, SV, and also masses of blood islands, 

 Bi, on the posterior ventral yolk regions. 



Figs. 23 and 24 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 islands, Bi. 



