428 Mr. G. C. Robson on the 
for Cyclostoma (4). These ridges are sometimes of consider- 
able length. 
‘The crystalline style (Pl. XV. fig. 3) fits closely into its 
sac and is a relatively large cylindrical body of hyaline 
appearance, usually with rounded ends. No attachment to 
the cuticular lining of the sac could be found. After ex- 
traction it invariably disperses in the fluid into which it is 
placed. 
The hepatopancreas, which extends from the apex down 
to the penultimate whorl, opens into the posterior chamber of 
the stomach by a single broad and short duct near to and 
on the same side as the opening of the cesophagus. 
The ¢ntestine leaves the pylorus and curls round the end 
of the style-sac to its anterior face, runs backwards along- 
side the sac till it reaches the face of the posterior chamber 
of the stomach, when it turns vertically and then runs 
forwards to the anus. ‘he intestinal wall is folded into a 
well-defined ty phlosole, which extends almost up.to the pylorus. 
Pedal Gland. 
A well-developed pedal gland is present. It is possible 
that it is by the aid of the secretion from this gland that the 
animal adheres to surface-films. Among other freshwater 
‘Teenioglossa such a gland has been described for Valvata (12). 
The Respiratory and Circulatory System. 
There is a single monopectinate gill (PI. XV. fig. 5) lying 
somewhat diagonally in the mantle-cavity, with its anterior 
extremity between the tentacles and its posterior extremity 
rather to the left; it therefore lies roughly parallel to the 
rectum. Its filaments * diminish gradually in size anteriorly 
and posteriorly, those of about the median third being much 
Jarger than the rest. 
It is almost impossible in sections of a whole animal 
to make certain that the gill-filaments are cut exactly 
transversely ; but from examination of a large number of 
preparations it would seem that in P. jenkinsi they are more 
lanceolate in section than in P. ulve. The supporting 
membranes of the filaments are very long and thin. 
There is evident no modification of the gill or mantle- 
cavity, although the animal is able to live out of water for at 
least several hours. No positive trace of a hypobranchial 
gland could be found. 
The heart lies in a capacious pericardium, which is situated 
in the usual position. The auricle lies in front of the 
ventricle and is smaller than the latter; its walls, as usual, 
* Twenty-seven to thirty in number, 
