ON SPERMATOGENESIS IN THE RAT. 
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made out from sections stained with hsematoxylin, but in 
chloride of gold preparations the cell outlines are rendered very 
distinct (PI. XXIII, fig. 14, c ). The nuclei are spherical, of a 
diameter of 5 n, and are faintly stained by hsematoxylin ; they 
possess a nuclear membrane, and a scanty network of chromatin. 
Between the nucleus and protoplasm of the cell a clear space 
makes its appearance, fitting like a cap over part of the nucleus, 
and in the neighbourhood of the clear cap a small chromatic 
granule is usually to be seen (PI. XXII, figs. 8, 9, c ). 
Stained with chloride of gold, the young spermatozoa presents 
an appearance such as is represented in fig. 14. There is a 
small accessory corpuscle attached to the nucleus, which 
subsequently becomes separated from it by a small vesicle 
which seems to be derived from the accessory corpuscle (fig. 
14, e). 
A few minute fatty granules are seen dotted about in the 
protoplasm of these cells, in osmic acid preparations, and the 
accessory corpuscles are also to be seen (fig. 15). It is 
difficult to make out clearly what is the origin of the clear 
space which is seen in haematoxylin preparations between 
part of the nucleus and the protoplasm of the cell ; apparently 
it corresponds to the small vesicle seen in chloride of gold pre- 
parations, attaching the accessory corpuscle to the nucleus, 
which may be increased in size by the action of alcohol on the 
fresh cell. 
The groups of cells are separated from one another for a 
short time by bundles of spermatozoa, which extend between 
them (fig. 9), but when the spermatozoa have left the sup- 
porting cells, it becomes difficult to make out a separation into 
groups, and there appears to be a layer of cells, three or four 
deep, between the growing cells and the spermatozoa, for now 
only the thin protoplasmic strands of the supporting cells 
extend inwards between the groups, to the layer of granules in 
which the heads of the spermatozoa are now embedded (PI. 
XXII, fig. 10). And now the stage of fig. 1 is again reached. In 
this stage the young spermatozoa present a different appearance ; 
they are apparently free in the tubule, having been set at 
