FiGUKK 320. — Embryo bone marrow. Composite made from 'A places on the same slide — the long 

 cluster of cells from 1 area, 6 cells from a nearby area, and 3 from another area. Emljryo incubated 

 12 days. Nearly the same age as embryo used for preceding plate, yet definitely more advanced 

 in development. 1,370 X. 



1-3 Primordial osteogenic cells. Cell 2 is more differ- 13, 14 Probably belong to the granulocyte series. 



15 A cell with magenta spheres in the cytosome. 



16 Heterophil mesomyelocyte. 

 17-19 All these cells are mature heterophil granulocytes. 



20 Late polychromatic erythrocyte with fractured 

 cytosome, a technic artifact. 



21 Mature embryo erythrocyte of a later generation. 



5-9 

 10 



11, 12 



Primordial osteogenic cells. Cell 2 is more differ- 

 entiated than 1 and 3. 



Primordial osteogenic cell with 2 magenta granules 

 and 5 magenta spheres. 

 Large young osteoblasts. 



A primordial osteogenic cell or granuloblast in 

 mitosis, early anaphase. 

 Aletagranuloblasis. The identification could have 

 been made more certain had they been fi.\ed in 

 their spherical shape. 



144 



