462 H. E. JORDAN 
conclusions exists covering these disputed points; this need not 
be here again reviewed; it is fully covered in a number of recent 
works (e.g., Downey,’ Ringoen?!). 
The superior feature of the frog material pertains primarily to 
the absence of special eosinophilic leucocytes. The presence of 
such types—with fine eosinophilic granules, as in guinea-pig and 
rabbit, and ellipsoidal eosinophilic granules, as in sauropsida and 
certain fishes—greatly confuses the picture in these forms. In 
the marrow of the frog the neutrophilic ‘special’ granulocytes 
and the eosinophils are clearly distinguishable from their earliest 
stages of development from the common lymphocyte ancestor. 
The neutrophilic granulocytes show at first an oxyphilic halo 
about the centrosome, which early becomes granular, the granu- 
lation spreading throughout the entire cell, the granules always 
being of a lighter or darker lilac color. The eosinophils, on the 
other hand, begin their differentiation from the parent lympho- 
cyte by the elaboration of a few minute deep-staining (purple) 
eosinophilic granules. These gradually increase in number and 
size, and assume a more brilliantly red (or orange-red) color. 
No basophilic granules (i.e., blue-staining) were seen among the 
eosinophilic granules at any stage of the development of this 
type of granulocytes. The earliest granules are, it is true, of 
purple-red color and apparently less oxyphilic than the definitive 
granules, but there is no evidence of a differentiation of definitely 
basophil granules into eosinophil granules. The definitive gran- 
ules, moreover, have a lighter-staining (less dense) center, giving 
the appearance of a ring-shaped structure. This appearance is 
due to a rarefaction of the center of the granules coincident with 
its growth. The growth of the granules, and their change into 
more intensively oxyphilic granules is apparently due largely to 
a dilution of their substance, specially pronounced in the center. 
Downey® comes to the conclusion, on the basis of his study of 
the marrow of the guinea-pig, that the eosinophilic granules 
develop from basophilic predecessors. His illustrations show 
deep blue-staining granules among eosinophilic granules in the 
eosinophilic myelocytes. Such blue-staining granules never 
appear in the eosinophilic myelocytes of frog in my material; 
