124 
Thos. H. Montgomen’, jr. 
But in addition to tliese major size differences tliere is a third or 
minor difference that was not specially noted in my first paper. It is 
that the spermatocytes, spermatids and spermatozoa of follicle 2 are in- 
variably somewhat smaller than those of foUicles 4 — 6. This second 
follicle is always the most narrow and is always constricted at one point 
(text figirre). Thus on PL IX cells of the second follicle are represented 
in figs. 9 — 15, and it will be seen that the several stages there sIiowti are 
always smaller than correspondent stages of the other follicles exhibited 
011 the Same plate. 
Thus there are three constant size differences of the spermatozoa, 
the largest in follicles 1 and 3, the smallest in foUicle 2, and ones of mter- 
mediate size in follicles 4 — 6. 
Xow what produces these cellular growth differences in the different 
follicles? In the paper of 1898 I concluded (p. 36) that „the greater size 
of the cells in the follicles 1 and 3 must be due to thetr recemng a greater 
amount of food than those in follicles 2, 4, 5 and 6. That is to say, the 
follicles 1 and 3 must be nourished by a richer blood supply”. That con- 
clusion was correct with regard to nutritional differences, but probably 
wrong is ascribing them to the direct difference of the blood received. 
For I now find that the size differences of the spermatocytes are due 
to differences in the folhcular nurse cells of the testis. Fach testis (text 
figure) has an elastic outer sheath, containing red pigment and numerous 
tracheae. IVithin this is a non-pigmented sheath, continuations of which 
compose the interfollicular septa. A portion of such a septum is shown 
in fig. 37, PL IX; it is composed of a dense tissue, shown by fine stippling, 
with occasional coarse fibrUs, isolated smaU nuclei and scattered cliroma- 
tin particles, and tracheae (t). Eesting upon the inner surfaces of the 
inner sheath and the septa are the nurse cells, ceUs with delicately fibrUlar 
cytoplasm and lai'ge nuclei (fn.) of quite irregulär forms. These nurse 
ceUs are excessively branched, and their branches interlace between the 
sperni cells and bind them into spermatocytes. It would be impossible 
to follow all the branches of such a nurse cell without recourse to maceration 
methods, consequently I have no data to offer with regard to their cell 
bodies. But the relative sizes of theh nuclei may be compared, even 
though the larger of these may extend over several sections. To deter- 
mine whether the nurse cell nuclei differ in size in the several follicles, 
I have compared their proportions by drawing to scale with the camera 
lucida a considerable number of them from all the follicles of the testis. 
In doing this I chose at random every eighth or tenth section of a series 
so as to exclude drawing any one nucleus twice, drew only those foUicle 
