62 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
84 (pi. 15) represents two such free cells considerably smaller but 
lying side by side as if originated by division of a free stalked cell. 
Partly imbedded in the nucleus is a mass of archoplasm (arch.) 
which in the second cell (b) has divided into two masses as if prepar¬ 
ing for cell division. In plate 15, figure 85, is represented another 
free cell, apparently of the same kind, in the metaphase of karyo- 
kinesis. The asters are well developed and the spindle is very dis¬ 
tinct. The outline of the original nucleus is still visible. 
The free cells are found in that part of the follicle where the sperma- 
tocysts are fully developed. They are not common. I see no way of 
accounting for them except on the assumption that they are the spheri¬ 
cal end cells of the stalk (pi. 12, fig. 5, st. c.) set free. There are no 
isolated free spermatogones of the usual kind, the primary sperma¬ 
togones being found in the immediate neighborhood of the grand¬ 
mother stem cell. 
If we compare figure 85 (pi. 15) with the next (pi. 15, fig. 86), a 
spermatocyte — a spermatocyte from the unusually large cytocysts 
already referred to (pi. 13, fig. 36) and which give rise to the giant 
spermatid (pi. 14, fig. 46; pi. 17, fig. 138) — the question arises 
whether these free stem cells do not give rise to the giant spermato¬ 
cytes. There are good reasons for assuming that such is the case. 
Yet I do not feel that the evidence in this case is sufficient to justify a 
definite statement. It needs further investigation in other forms. 
Should the above hypothesis prove true, we would here have a case 
where the primordial germ cell grows like an egg without dividing 
and finally segments into a number of cells, spermatocytes, the period 
of growth — unlike the usual mode — preceding the division period 
as is the case with a segmenting egg. 
The . Grandmother Stem Cell. 
In some follicles a very large cell is found which deserves special 
attention. Unlike the free stalked cells considered above, this cell 
is usually surrounded by a compact mass of small cells forming, as 
it were, a heap, in the center of which the large cell is invariably 
found. I have named it the grandmother stem cell. I have never 
found more than one of these in a follicle, and never more than four 
in a testis (pi. 12, fig. 5, g. m. c.). As there are eight follicles in a 
