ON SPERMATOGENESIS IN THE RAT. 35 7 
situated at about the centre of the cell ; the accessory 
corpuscle is to be seen in these cells attached to the nucleus 
by a minute vesicle, and another small refracting granule is 
attached to the nuclear membrane, at the point from which 
the development of the body of the spermatozoon is about to 
begin. There are also a few minute fatty granules dotted 
about in the protoplasm (fig. 15, c). The manner in 
which these cells develop into spermatozoa is represented by 
fig. 22. 
The nuclear membrane over the outer hemisphere of the 
nucleus becomes slightly thickened, and at the opposite pole 
of the nucleus, where the small granule is attached, a fine 
filament makes its appearance in the protoplasm, and extends 
from the nucleus to the surface of the cell, where it is pro- 
longed by a delicate protoplasmic filament, the rudiment of 
the tail of the spermatozoon. At this time the 1 accessory 
corpuscle breaks away from the nucleus and becomes embedded 
in the protoplasm at the inner part of the cell, where it remains 
inactive during the remainder of the process, to be finally cast 
off with the protoplasmic residue when the development is 
nearly completed. The protoplasm of the cell now becomes 
collected entirely at the inner part of the nucleus, leaving the 
outer hemisphere, upon which is the thickened membrane, 
covered only by the clear cap (22, d). 
This corresponds to the stage of development represented by 
figs. 1 and 12, at which the young spermatozoa appear to be 
free in the tubule. The nuclei of the cells are now commencing 
to elongate in the radial direction and to take on the oval form, 
and a small prominence becomes visible at the outer pole of 
the nucleus at the centre of the thickened membrane, the 
“ bouton terminal of Renson (fig. 22, e ). It is at this stage 
that the grouping in connection with the supporting cells is first 
seen. Fig. 16 represents a group of young spermatozoa em- 
bedded in the protoplasm of a supporting cell, but the nucleus 
of the body cannot be seen, and the protoplasm appears to be 
1 I have not been able to make out what the origin of the accessory 
corpuscle is. Perhaps it is derived from the nucleus of the growing cell. 
