FiGiTRES 322-328. — Embryo bone-marrow cells and serum. 2,470 X. 



322 Stained serum fluid and granules tliat almost always 

 cover the cells in embryo bone-marrow smears. 

 Embryo incubated 19 days 18 hours. Figures 319, 

 320, and 321 drawn with these granules and stained 

 serum omitted. 



323 A large young osteoblast, not as typical as those 

 shown in figure 320. Embryo incubated 14 days 11 

 hours. 



324 Primordial osteogenic cell. Some vacuoles with 

 magenta crescents. Enibr_vo incubated 11 days 21 

 hours. 



325 Slightly smudged primordial osteogenic cell. Same 

 slide as in preceding figure. 



Figures 326, 327: Mononuclear osteoclasis. Same slide as 

 in figure 324. 



Faint acidophilic material filling the cytoplasmic 

 spaces on the upper left side of the nucleus is charac- 

 teristic of osteoclasts from adult bone marrow. 

 Compare with figure 398. 

 Two magenta spheres at the tip of the cell. 

 Mononuclear osteoclast with numerous magenta 

 spheres. At the left are acidophilic bodies charac- 

 teristic of the osteoclast. Embryo incubated 16 days 

 19 hours. 



326 



327 

 328 



148 



