CYTOPLASMIC INCLUSIONS OF THE GERM-CELLS. 585 
brane. In some generations of secondary spermatogonia this 
latter structure is not demonstrable till later. This body is 
the first visible sign of the Nebenkern of Pulmonates, and it 
may possibly have been present in the stage drawn in PL 31, 
fig. 17, but may not be plain enough to make its detection 
possible. 
In PI. 32, fig. 24, is drawn a spermatogonium of the genera- 
tion shown in Text-fig*. 2, fig. ii, at 2. The Nebenkern ( N.K .) is 
quite easily seen to consist of several straight rods. In PI. 32, 
fig. 29, the Nebenkern of another generation of spermatogonia 
is shown. The fate of the Nebenkern and mitochondria of 
these generations has already been followed out. 
Another sort of male generation of cells appears in the 
following way : In Text-fig. 3, i, is drawn a lumen in which 
nearly all the germinal epithelial cells have thrown off their 
indifference and have become large peculiar cells. The 
epithelium from which such cells arise consists of a single 
layer of cells, yolk cells being either exhausted or completely 
absent. This is shown in the plan on PI. 29, fig. 1, at the 
Roman figures i-iv. 
In PI. 31, fig. 19, the cell at ii in PI. 29, fig. 1, is drawn 
at high magnification. It lies on the epithelium projecting* 
into the lumen in a different way from PL 31, fig. 17. 
The nucleus still has the chromatin lumps which stain some- 
what lightly, and there are two nucleoli which are hollow 
spheres, as far as one can ascertain. At any rate, their 
centre does not stain so heavily as the periphery. The lumps 
gradually become elongated and join up to form a wide reticu- 
lum (PL 31, fig. 20). Now, the plasma in fig. 19 is seen 
to contain to one side of the nucleus, the usual zone 
which here and there has a granule. In the next stage the 
granules have become quite plain and are seen to consist of 
the ring-like mitochondria already described from the figures 
in Pl. 31. In fig. 20 the zone of thickened cytoplasm has 
spread right around to the opposite side of the nucleus but 
as yet no distinct mitochondria have appeared on this side (Z.) 
There is rarely any other structure to be made out in the 
VuL. 62, PART 4. KEW SERIES. 40 
