PLATE 3 



EXI'LA.VATION OF FIGURES 



5 Part of the spleen, adjacent to the surrounding loose mesenchyme. Large 

 group of hemocytoblasts within the sinus, beginning their differentiation into 

 erythrocytes. Eighth day of incubation. 



6 Part of the spleen from the center of the organ. S.AyiL, sinus anlage. 

 Xinth dav of incubation. 



314 



