PROSTATE GLANDS OF THE EARTHWORMS OF THE FAMILY MEGASCOLECID^. 445 
ficial nuclei of the gland substance itself. Where a strand of connective tissue joins 
the gland, it fuses with it completely and becomes continuous with the substance 
of the gland. 
The cavities in the hollow aggregates of nuclei become continued into the main 
prostatic duct. The aggregates described under ( b ) are apparently masses which 
are not yet cavitated, and those of (c) may be a still earlier stage. Each aggregate 
seems destined to become a lobule of the adult gland. 
The main duct appears as a thick prolongation of the glandular mass towards the 
surface. It consists of a large mass of indifferent cells, pierced throughout by a 
canal which has its own epithelial lining. Where it is continued outwards from the 
gland, the duct is nearly as thick as the glandular mass itself, but it becomes thinner 
as it approaches the surface. In the ental portion the lumen with its lining epi- 
thelium is about a quarter of the diameter of the whole, but nearer the surface the 
lumen narrows considerably — more, relatively, than the duct as a whole. 
There is no sharp division between the gland and duct — the protoplasm of the 
gland is continuous with that of the duct ; but the nuclei become less dense in the 
duct-wall. There is as yet no differentiation of muscular tissue in the wall of 
the duct ; the nuclei of<the ental portion are ovoid and without definite arrangement ; 
in the ectal portion, however, they are already elongated, and lie transversely to 
the axis of the tube. There is no connective tissue capsule on the duct. 
(5) The Earliest Stages in the Development of the Prostate (fig. 6). 
Even in a small worm 1'7 mm. in greatest diameter, long before any outward 
sign of sexuality appears, the vasa deferentia and prostates are present. 
On approaching the site of the prostate in the series of sections, the muscular 
layer of the body-wall is seen to show an infiltration of connective tissue cells — 
strands of cells passing through the wall more or less, vertically to the surface. 
These cells are in' part almost naked nuclei, homogeneous in texture ; elongated, 
spindle-shaped, or irregular in outline ; sometimes clothed or accompanied by 
amorphous matter representing the cell-body. They do not appear to differ from 
the connective tissue nuclei of the body-wall, into which they shade off. The 
peritoneal lining of the body-cavity is thickened in this region, and appears as a 
well-marked layer of connective tissue ; the cellular infiltration in the muscular 
layer is continuous with this thickened peritoneum, and also, as we shall see, with 
the duct of the gland as it passes through the body-wall. The two vasa deferentia 
lie close together on the body-wall. 
The gland itself makes its first appearance in the series of sections as a dense 
mass of nuclei, continuous with the thickened connective tissue representing the 
peritoneal layer. Some of these nuclei almost immediately begin to group them- 
selves into tubes, but the tubes are evidently constituted of the same elements as 
the general cell proliferation. There is no sign of a capsule over the extremity of 
