64 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
The latter hypothesis assumed the certainty of a fact in my mind 
when I discovered that the bodies imbedded in the outer cytoplasm 
of the cell are real nuclei (not granules as I had supposed) and further 
that immediately connected with the grandmother stem cell, there 
are cells which divide, one product of division being in fact a primary 
spermatogone. I found further that only in this region immediately 
surrounding the grandmother stem cell, a single cell can be found 
dividing, something to be found nowhere else, as all the cells of a 
gonocyst divide at the same time. More careful examination showed 
that each primary spermatogone is accompanied by at least one small 
nucleus at its periphery, which proved to be the “anlage” of the future 
cyst cells. 
«/ 
The grandmother stem cell is irregular in outline, the cytoplasm 
all over its surface being prolonged into cytoplasmic' processes which 
on a superficial examination seem to extend out between the numerous 
smaller cells surrounding it. Its general outline is about the same 
in whatever plane looked at, the main body of the cell being a sphere 
(pi. 15, fig. 56). It has a large nucleus which is usually regular and 
spherical or oval. In many cases, there is on one side of the nucleus, 
an unstained portion resembling a vacuole, as large as or even larger 
than the nucleus itself. Within this area, there is often a spherical 
body suggesting a sphere with its archoplasm, but more frequently 
a mass of granules resembling chromatin in staining reaction (pi. 12, 
fig. 4). Occasionally this is double and looks as if it might be part 
of a fragmented nucleus, but less rich in chromatin than the main 
part of the nucleus (pi. 15, fig. 57a). In most cases, the chromatin 
forms a network, but occasionally it is compacted into a mass (pi. 15, 
fig. 56). Granules resembling chromatin are sometimes to be seen 
also in the cytoplasm, usually contained in rather small vacuoles. 
The cytoplasm of these cells is very much the same in all. It is 
distinguished from that of all other cells of the testis by its resistance 
to stains. It is apparently devoid of those cytoplasmic granules 
which take the stain as it seems also devoid of cytoreticulum and 
cytomierosomes. In appearance the whole cytoplasm resembles 
archoplasm. It stains well in saffranin, but remains practically 
unstained in haematoxylin and borax carmine and most nuclear stains 
that I have used. In this, too, it resembles archoplasm. I consider 
it the most undifferentiated cell in the testis. I shall present other 
good reasons for believing this to be the real original germ cell, for 
which reason I have called it the grandmother stem cell. 
