372 MR. HANCOCK ON THE ANATOMY OF THE FRESHWATER 
it that the tentacular disc is a little flattened, proving that this 
point corresponds to the space between the arms in Plumatella ; 
indeed, in some points of view, the angles formed by this flatten- 
ing have not a little the appearance of rudimentary arms just 
sprouting. 
The cesophagus descends at once in a straight line from the 
oral opening. In Fredericella, Pl. III. figs. 1 f & 2 6, it is rather 
short and wide, and the walls, which are thick and fleshy, are 
parallel throughout, except at the commencement, where they 
are a little bulged, forming a sort cf pharynx which is lined with 
vibratile cilia: the other extremity communicates with the 
stomach by a distinct valvular orifice, Pl. III. figs. 1 g & 2e, 
the cardiac, projecting downwards. The whole surface is covered 
with minute circular cells resembling very much the peculiar 
structure observed in the marine species, and pointed out by Dr. 
Farre, in his valuable paper on the Marine Ascidian Polypes 
published in the ‘ Philosophical Transactions’ for 1837, 
The stomach, figs. 1 2 & 2 d, is more than twice the length of 
the cesophagus, tapering slightly downwards and truncate above ; 
the lower extremity being obtuse: the walls, lke those of the 
oesophagus, are thick and fleshy, and are covered with numerous, 
minute, close-set cells of a glandular character. The pyloric 
orifice is circular and well marked, and has the appearance of 
being guarded by a sphincter muscle; it is likewise supplied 
with vibratile cilia which extend some little way into the 
stomach. This orifice is situated above, at one side and a little 
below the cardiac opening. The intestine, figs. 1 & 2, %, ¢, is 
straight, and a little longer than, and nearly as wide as, the 
esophagus, with which it hes in contact, and to which it is 
apparently attached ; the pyloric extremity is obtusely pointed, 
and communicates by the side with the stomach ; from thence the 
intestine tapers a little upwards towards the anal extremity, 
which, turning outwards, passes through the tentacular sheath 
just below its attachment to the disc supporting the tentacles, 
and there terminates in an obtuse perforated point, figs. 1 & 2 7 
& f, which can be either protruded or retracted, to a considerable 
extent, at the will of the animal. The whole of the alimentary 
