Freshwater Bryozoa, with descriptions of new Species. 177 
in some points of view the angles formed by this flattening 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. I. figs. 1 f & 2 4, 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 of pharynx which is lined 
with vibratile cilia: the other extremity communicates with the 
stomach by a distinct valvular orifice, Pl. IL. figs. 1 g & 2¢— 
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, like those of 
the cesophagus, are thick and fleshy, and are covered with nu- 
merous, 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%, e, is straight, and 
a little longer than and nearly as wide as the cesophagus, with 
which it lies 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 out- 
wards, passes through the tentacular sheath just below its attach- 
ment to the disc supporting the tentacles, and there terminates 
in an obtuse perforated point, figs. 1 & 27 & f, which can be 
either protruded or retracted to a considerable extent at the will 
of the animal. The whole of the alimentary canal is highly irri- 
table, particularly the cesophagus and stomach, in the walls of 
both of which, minute, transverse strize are distinctly visible, pro- 
bably indicating the presence of muscles. The stomach is per- 
petually in motion when the animal is displayed, contracting in 
an undulating or vermicular manner from above downwards. 
The contractions of the cesophagus, too, are very decided on re- 
ceiving food, which for a second or two rests in the pharyngeal 
enlargement, and is then hurried to the stomach with great 
rapidity. 
The alimentary canal of Plumatella and Alcyonella does not 
vary in any important manner from that of Fredericella. In the 
Ann. & Mag. N. Hist. Ser. 2. Vol. v. 12 
