PLATE 1 



EXPLANATION OF FIGURES 



All figures were drawn with a Leitz 1/16 objctive, a no. 1 ocular, and a camera 

 lucida. The magnification is about 1600 diameters. 



1 Hemoblast. The nucleus appears as a central, pale, homogeneous, circular 

 area. Above the nucleus is a small, clear, circular area, the centrosphere, closely 

 applied to which at the left is a deeply staining, collapsed loop-like structure, the 

 Golgi apparatus. Throughout the cytoplasm, for the most part near the nuclear 

 wall, are scattered granular and bacillary mitochondria. 



2 Hemoblast. In this cell the Golgi apparatus encircles the centrosphere, 

 and appears to consist of several fused rods and granules. The cytoplasm con- 

 tains a few vesicular mitochondria. 



3 Later hemoblast, or young mononucleated giant-cell, apparently in ame- 

 boid motion. The mitochondria are largely of bacillary form. Along the upper 

 border the mitochondria are aggregated into spherical group suggesting either a 

 forming or a disintegrating Golgi apparatus. 



4 Hemoblast. The Golgi apparatus consists of a large, apparently continu- 

 ous, bilobed net, closely applied to the nucleus. The mitochondria are predomi- 

 nantly of the bacillary form. A few mitochondria are shown scattered over the 

 central nucleus. 



5 Young polymorphokaryocyte. The enlarged nucleus is still relatively 

 simple, consisting of two large lobes connected by a narrow bridge of nuclear 

 material. Within the nuclear concavity, slightly to one side, the usual location 

 of the now fragmenting centrosome, is situated an intricate network of delicate 

 and deeply staining threads, the Golgi apparatus. The cytoplasm contains 

 mostly short, rod-shaped mitochondria, with a few granules and vesicles. A nar- 

 row, clear, non-granular exoplasmic layer is here very conspicuous. 



6 Older polymorphokaryocyte (megakaryocyte). The Golgi apparatus is not 

 here shown. The cytoplasm is packed with exclusively granular mitochondria. 



7 Older hemogenic giant-cell with complex polymorphous nucleus (polymor- 

 phokaryocyte). The Golgi apparatus is shown to the left. It consists of an 

 intricate skein of deeply staining threads. The mitochondria are predomin- 

 antly vesicular. 



8 Section of preceding cell, 15m beyond the section of figure 7. The mito- 

 chondria are very abundant, including both granules and vesicles. 



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