BLOOD AND BONE-MARROW OF FROG 44] 
greatly with respect of size, and the presence or abundance of 
metachromatic granules. Moreover, certain of the pseudopods, 
especially isolated portions, contain masses of this basophilic and 
metachromatic granulation. Such bodies resemble very closely 
the blood-platelets of mammals. 
There is abundant evidence, which will be detailed below, to 
show that the various blood-cells undergo further growth and 
development in passing from the blood spaces of the marrow to 
the general circulation; in view of which it may be inferred that 
the non-granular lymphocytes of the marrow elaborate meta- 
chromatic granules after entering the blood stream. 
The nucleus of the lymphocyte likewise suffers a considerable 
change during the passage of the cell from the marrow to the 
circulation. ‘The nucleus of the medullary lymphocyte is vesic- 
ular; it contains a distinct plasmosome, several deeply chromatic 
karyosomes, many smaller chromatic granules ranged mainly 
along the nuclear membrane, and a very delicate chromatic 
reticulum (figs. 35 and 37). In general appearance it is much 
clearer and lighter staining than the nucleus of the circulatory 
lymphocyte. 
The attraction sphere of the lymphocytes is usually masked 
by the basophilic granulation. Occasionally it appears very 
conspicuously as a spheroidal clear area containing a centrosome 
or diplosome (fig. 10). 
While the evidence at hand does not permit of a final conclu- 
sion regarding the genetic relationship between lymphocyte and 
platelet, the striking resemblance of the lymphocyte pseudopods 
and their constriction products to mammalian blood-platelets is 
unmistakable. 
3. The eosinophilic leucocytes. This type of cell will be fully 
discussed below in connection with the description of its myelo- 
cyte ancestors. It will suffice here to state that in its adult con- 
dition it contains a polymorph or, in rare instances, a multiple 
nucleus, generally located at one pole of the spheroidal cell. Oc- 
casionally a mononucleated form may occur. Figure 11 shows a 
binucleated form. The spheroidal eosinophilic granules are of 
approximately uniform size. They appear hollow, or annular, 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 25, No. 4 
