A 



B 



Figure 332. — Embryo thymus. 



Embryo incubated 9 days 4 houre. Mesenchymal 

 cells of the embryo thymus early in its development. 

 1,370X. 



1 Primordial cell with a nucleolus. 



2 A rounded primordial cell. 



3, 4 Cells in which the cytoplasm is merged with the 

 stained serum. 



5 Naked nucleus. 



6 Broken, naked nucleus. 



7 Shrunken, broken cells. 



8 Strands of basichromatin from broken n'.tclei. 



B Embryo incubated 11 days 10 hours. 1,370X. 

 1 Lymphoblast. 

 2, 3 Early immature lymphocytes. 

 4, 5 Late immature lymphocytes. 



6, 7 Mitosis, prophase. Cells probably are developing 

 lymphocytes. 

 8-10 Smudged, naked nuclei. 



11, 12: Identification uncertain; either macrophages or heter- 

 ophil promyelocytes. 



11 Closely resembles a promyelocyte. 



12 A highly atypical cell. It contains magenta 

 spheres like the primordial osteogenic cell. 



170 



