442 H. E. JORDAN 
due probably to difference in density between center and pe- 
riphery. The granules are imbedded in a lightly basophilic 
substratum. Eosinophils constitute only a very small propor- 
tion of the leucocytic content of the frog’s blood. In the winter 
specimens the eosinophils are rarer than the basophils; in the fall 
specimens they are relatively more numerous. 
4. The basophilic leucocytes. This type of cell is somewhat 
smaller than the eosinophil. It is approximately the size of the . 
medium-sized lymphocyte (fig. 12). Its nucleus is centrally 
located and vesicular. The nucleus contains a very delicate 
reticulum. The cytoplasm is closely packed with spherical baso- 
philic, lilac-colored granules, larger on the average than the 
eosinophilic granules, but varying somewhat in size and shape, 
certain granules having an oval form. In the marrow these 
cells have a deeply staining nucleus (figs. 51 to 53) and the cyto- 
plasmic granules take a deep blue color with Wright’s stain. 
5. The neutrophilic leucocytes. This is by far the most abun- 
dant type of leucocyte (figs. 13 to 26). Its nucleus is generally 
polymorphous. Mono- and binucleated forms also occur. The 
cytoplasm consists of a homogeneous basophilic (blue-staining) 
substratum, throughout which are scattered fine metachromatic 
(neutrophilic) granules. The granules are always very small, 
but vary in size from a scarcely perceptible dust to very definite 
spheroidal granules of light lilac color. The resemblance to the 
polymorphonuclear neutrophilic leucocytes of mammals (com- 
pare figs. 22 and 23) is striking. In areas where the neutro- 
philic granules are sparse, the basophilic (blue) substratum also 
appears granular. 
The most conspicuous feature of these cells, aside from their 
characteristic polymorphous nucleus, is the attraction sphere. 
‘This is generally situated within the concavity of the lobulated 
nucleus (figs. 13, 16, 18, and 19). The neutrophilic granules are 
arranged in lines radiating from the sphere (fig. 17). The attrac- 
tion sphere may consist of a spherical mass of minute granules 
imbedded in a denser protoplasm (figs. 16, 21, 23, and 25) or it 
may occur as a Clear area (centrosphere) containing centrally -a 
deep-staining granule or centrosome (centriole) (figs. 13, 17, 18, 
