734 THOS. H. MONTGOMERY, JR. 
Spermatogonia may always be distinguished from spermato- 
cytes of the earlier growth period by the following characteristics: 
(1) the spermatogonia are arranged in radial rosettes; (2) each 
of them possesses a mitosome in the rest stage; (3) their plasmo- 
somes do not lie against the nuclear membrane; (4) their cyto- 
plasmic mass is relatively larger; (5) they never possess filiform 
mitochondria. These differences are mentioned in order to fore- 
stall any objections that might be raised to our seriation of stages, 
such as confusing a telophase of a penultimate spermatogonium 
with that of an ultimate one, an important point, for telophases 
of ultimate spermatogonia are necessarily first spermatocytes. 
There is no possibility of confusing spermatogonia with any other 
cell generations than early spermatocytes, for the successive 
stages of the spermatogenesis follow each other along the length 
of each testicular follicle in fairly regular order. 
In testes of adult individuals are found two generations of 
spermatogonia, which it will be convenient to call the ‘penulti- 
mate’ and the ‘ultimate,’ these terms being preferable to ‘pri- 
mary’ and ‘secondary’ of most writers, for the reason that pri- 
mary and secondary employed in the strict sense should refer to 
the first two generations of the germinal cycle. Whether there 
are three generations of them in adults was not positively ascer- 
tained. Fig. 1 represents a penultimate, and fig. 3 a group of 
ultimate, spermatogonia, and these figures give a fair example of 
the usual differences between the two. The penultimate spermat- 
ogonia are larger, usually shorter, and their number within a 
cyst (rosette) is only half that of the ultimate spermatogonia. 
In resting cells of both spermatogonial generations a portion of 
the chromatin is always arranged on the nuclear membrane in the 
form of a chromatin plate, in the immediate vicinity of the idio- 
zome (figs. land 3). The local connection of these two structures 
is invariable, no matter what the position of the idiozome may be; 
this relation was overlooked in my paper of 1898. 
In equatorial plates of the spermatogonia are to be counted 
fourteen chromosomes (fig. 2), twelve of which are autosomes as 
detailed particularly in my papers of 1906 and 1910. The very 
