450 PROFESSOR J. STEPHENSON AND PROFESSOR HARU RAM ON THE 
of grannies are seen pushing their way through this layer. The outer investment 
of muscular fibres penetrates the gland substance. Finally, the gland substance dis- 
appears, leaving only an epithelial layer and a muscular coat. 
After the disappearance of the glandular substance the lumen of the tube is wide, 
and the wall thin ; the muscular fibres have a circular disposition. The lumen 
becomes smaller, and the muscular coat thicker, while the epithelial lining is lower 
than at first. This is the constitution of the main portion of the duct. Ultimately 
the lumen of the duct becomes minute, and joins the sac of a penial seta. 
The terminal portion of the vas deferens has no visible epithelial lining, except 
just at its end, where it becomes dilated ; it has a double muscular coat, the inner 
layer of longitudinal, the outer of circular, fibres. It opens close to but separately 
from the prostatic duct, on a papilla which is sunk in a depression of the ventral 
surface. 
(4) Regeneration of Glandular Tissue , and Summary. 
It would appear, from what has preceded, that in the young and non-functioning 
gland the glandular tissue consists of separate cells, a number or all of which abut 
on to the central lumen by narrow necks. Later, the cells largely break up to form 
the secretion, which, in the form of granules, travels along the narrow necks to 
reach the lumen. Finally, the cellular structure disappears altogether, the granules 
finding their way along channels established in the situation of the necks of the 
former cells. 
The gland apparently regenerates from the periphery. In one specimen the 
peripheral region of the gland was largely made up of distinct cells, of various 
shapes, separated from each other, by clefts and spaces ; in many of these cells the 
formation of discrete spherical granules had not begun. Such showed a homogeneous 
finely granular cytoplasm which stained deeply ; they almost certainly did not send 
prolongations, as yet, to the lumen of the canal, and all contained a nucleus. The 
size of the nucleus varied from 2 '5 to 5 /r in diameter ; the form was sometimes 
irregular ; there was a distinct nuclear membrane, granular contents, and a con- 
O 7 7 O 7 
spicuous central chromatic body. The more central portion of the gland consisted 
of the usual masses of spherical granules, as previously described. 
The tubular prostate of Eutyphceus, therefore, consists essentially of elongated' 
cells of varying height, which probably all debouch into the lumen of the tube. 
These cells are not arranged in definite layers. The secretion is produced in the 
form of granules, which are discharged as such. The cells appear to disintegrate 
during the process, and to be regenerated from the periphery of the gland. 
The Prostate of Dichogaster. 
We have seen that in Pheretima the lobate prostate is mesodermal in origin, 
and is formed as a proliferation of the connective tissue of the lining of the ccelom 
