286 H. E. JORDAN 



(//) and its enveloping cytoplasm are of typically haemoblast 

 character. A delicate chromatic nuclear bridge still connects 

 the haemoblast nucleus with the mesenchyma nucleus. The 

 significance of this nuclear bridge is uncertain, but it plainly 

 reveals genetic relationship whatever its meaning in terms of 

 type of cell division. Such instances should definitely dispose 

 of the objection that all mesenchymal haemoblasts are migrants 

 from adjacent blood vessels. Haemoblasts are very variable 

 in form, due to the variable number and form of their pseudo- 

 pods (fig. 27). They must be regarded as capable of extensive 

 amoeboid motility. 



It is a matter of sufficient importance to warrant special 

 emphasis at this point, that between typical haemoblasts and 

 typical erythroblasts, next to be described, transition forms 

 exist abundantly (fig. 1 b) . The marks of transition pertain both 

 to the nucleus and the cytoplasm. The change is perhaps 

 most marked in the staining capacity of the cytoplasm. This 

 loses its intense basophily, and in Giemsa preparations becomes 

 a much lighter pink or grayish blue. This chemical alteration 

 inheres principally in the elaboration of a small amount of 

 haemoglobin. The cytoplasm shows also faintly a coarse wide- 

 meshed reticulum. And a distinct cell wall is now evident 

 (fig. 1 b), whereas the haemoblast is apparently a naked cell. 

 The nucleus becomes relatively smaller and more chromatic; 

 the nucleoli tend to disappear, and the nuclear reticulum be- 

 comes coarser, more granular and more chromatic. 



3) Erythroblasts. These cells are characterized by their slightly 

 smaller spherical nuclei and an acidophil cytoplasm generous 

 in amount (fig. 1 c). The nuclei generally lack distinct nucleoli 

 but contain a coarsely granular, intensely chromatic, nuclear 

 reticulum. The cytoplasm has frequently a finely granular 

 appearance (fig. 3 f). In Giemsa preparations the nucleus 

 stains blue, the cytoplasm a faint brownish pink. These cells 

 are much more uniform in size than the haemoblasts and are 

 generally mononuclear. They undergo very extensive mitotic 

 proliferation. The transition stages (figs. 1 b and 3 f) between 

 the haemoblast and the erythroblast, characterized by a bluish 



