464 H. E. JORDAN 
other leucocytes. This study does not touch the disputed ques- 
tion of the genetic relationship between the so-called histogenous 
and hemotogenous types of basophilic leucocytes. The litera- 
ture on this subject has been very fully reviewed in the recent 
papers of Maximow,'® Downey,’ and Ringoen.?®* This study is 
concerned only with the hemotogeneous type of mast-cells. My 
results are in accord with those of the above-mentioned authors, 
who conclude that in the mammals investigated (including 
guinea-pig and rabbit) the mast leucocytes represent a specific 
‘and independent line of granulocytes, of heteroplastic origin, 
with basophilic granules resulting from a specific activity of the 
protoplasm. 
In the marrow of the frog the first indication of mast-cells 
‘appears in the nuclear modification of the lymphocyte parent, 
namely, a relatively greater contraction and condensation of the 
central spheroidal nucleus, giving a deep-blue coloration and a 
more homogeneous character to this body. Coincident with 
these early nuclear alterations, minute basophilic (deep blue- 
‘staining) granules appear; these granules are, however, from the 
beginning larger than the ancestors of the eosinophilic granules. 
“They grow in size, exceeding that of the definitive eosinophilic 
granules, and maintain their original deep blue coloration. 
These cells also liberate granulated globules through segmenta- 
tion of pseudopods. As found in the blood, these cells show a 
centrally located, more vesicular nucleus, a somewhat larger 
size, and cytoplasmic granules of deep lilac color. There is not 
the slightest indication of a transformation of these basophilic 
‘granules into eosinophils at any stage, nor of any degeneration 
process connected with the formation of the granules. None of 
these cells were seen by me in mitosis at any stage. The cells 
apparently originate only heteroplastically from parent lym- 
phocytes, and form their granules by an endogenous process. 
These observations agree with those previously reported for the 
basophilic granulocytes in the turtle embryo.!!' Not only can 
both eosinophils and basophils be traced to the same type of 
lymphocyte, but the smaller granules of the youngest basophils 
are always considerably larger than the smallest eosinophilic 
