MUNSON: SPERMATOGENESIS OF PAPILIO. 
63 
double testis, all follicles do not have one of the cells. My first 
impressions consequently were that this is an abnormal growth of one 
of the gonocysts. From the general appearance of the grandmother 
stem cell and its connection with surrounding cells resembling an egg 
follicle, I suspected that it was a case of primary spermatogones grow¬ 
ing from the first, instead of dividing, as an oocyte or young egg. 
An examination of the developing ovary of a young larva reveals 
indeed a striking resemblance between the grandmother stem cell 
and the young growing egg. Excepting the irregular ones in the 
grandmother stem cell, the nuclei are strikingly similar, and the cyto¬ 
plasm of the young growing egg very strikingly resembles that of the 
grandmother stem cell. I found even that the young egg, like the 
grandmother stem cell, sends out protoplasmic processes to the sur¬ 
rounding follicle cells, and seems thus to have a protoplasmic connec¬ 
tion with each follicle cell. So far the resemblance is certainly striking. 
But in some transverse sections of the young ovarian tube — of which 
there are four, corresponding to the four follicles of the testis — the 
food or nurse cells (few in number and highly specialized, particu¬ 
larly as regards the nucleus), occupy the position held by the cortical 
nuclei in the grandmother stem cell. 
The fact that each testis has at least one, sometimes two, three, or 
four of these grandmother stem cells (pi. 12, fig. 8 b) seemed not to 
sustain the view that it is merely an abnormal or accidental growth 
of a spermatogone; while, the fact that every follicle does not seem 
to have such a cell, forbade me, as I thought, from assigning any 
great importance to it. Yet the origin of the primary spermatogones 
and the origin of the cyst cells surrounding the already developed gono¬ 
cysts remained a mystery, as no free primary spermatogones or pri¬ 
mordial germ substance could be seen. 
The significance of the grandmother stem cell assumed an entirely 
different aspect when I began to suspect that the testis has originally 
but a single lumen, and that the partitions separating the testis into 
four chambers or follicles appear gradually as the testis enlarges, 
so that the already formed gonocysts are included in each chamber. 
Consequently it does not matter much in which of these follicles the 
grandmother stem cell finally becomes lodged. The fact, too, that 
it is always close to the inner pigmented lining — (I have found only 
one instance where it was removed slightly from the peripheral wall) 
— seemed to suggest some original origin or function of this cell. 
