374 MR. HANCOCK ON THE ANATOMY OF THE FRESHWATER 
ter; it passes upward in a straight line parallel with the ceso- 
phagus, but unattached to it, and terminates in a rounded anal 
extremity, 7, immediately below the base of the tentacles where 
it perforates the tentacular sheath. The upper end of the 
stomach, close to the pyloric orifice, is furnished with vibratile 
cilia, and here the alimentary matters may be seen rapidly 
rotating by their influence. The feces are formed into small 
pellets, which, coming from the enlarged portion, pass up the 
intestine and are expelled at the anal orifice. The whole of the 
canal is as highly irritable as in the other species ; the stomach 
undulating from above downwards in the same manner, and the 
cesophagus is equally expert in transmitting food to the stomach. 
But neither in Paludicella nor in the species before alluded to 
does the pharyngeal swelling exhibit in any marked manner, the 
sudden puffings and contractions so conspicuous in the marine 
species, and noticed originally by Dr. Farre. 
On retraction of the polype, the alimentary canal of Paludi- 
cella is doubled upon itself in much the same way as in Bower- 
bankia. The basal disc of the tentacles is then brought down as 
far as the upper extremity of the stomach, and the consequence 
is that the intestine, fig. 2 h, is doubled upon itself a little above 
the enlargement, 7, and the cesophagus, e, is forced down by the 
side of the stomach, g, and turning upwards again is bent into 
the form of an 8. 
Vascular System.—This appears to be entirely wanting in 
these animals: a species of circulation nevertheless exists. I 
have seen, on two or three occasions, a pretty regular flow of the 
fluid in the visceral cavity of Pluwmatella and VFredericella. 
Under ordinary circumstances no fluid can be recognized in this 
cavity, from the apparent deficiency of blood-globules or corpus- 
cles of any kind. Such however probably exist, but the thick- 
ness and opacity of the cell-walls are sufficient to prevent the 
detection of minute bodies of this nature. On the occasions 
alluded to, some of the tissues of the animal appear to have been 
ruptured, and small fragmentary particles, mingling with the 
contained fluid, were perceived moving in certain directions. By 
the aid of these particles, which were numerous and of various 
