268 DR. A. RATTRAY ON THE ANATOMY, PHYSIOLOGY, 
elongated, tapering anteriorly, and widening posteriorly ; while its central part, or rachis, 
widens on the other hand from behind forward. The rows of teeth, from twenty-seven 
to thirty in number, are comparatively soft, though perfectly adapted for disintegrating 
the soft tissues of the Pteropods.and other animals on which they doubtless feed. 
Behind the buccal nucleus the cesophagus commences by a funnel-shaped dilatation 
(Plate XLIII. fig. 2, K) where the muscular fibres are stronger than elsewhere. This 
soon narrows into a tube-like intestinal canal, which runs along the central axis from 
one end of the animal to the other, almost in a straight line (Plate XLIII. fig. 1,1), 
varying in diameter, when quiescent, from one-sixth to one-fifteenth of the width of the 
body. Its coats, and those of the stomach and rectum, have a longitudinal and trans- 
verse layer of involuntary muscular fibres (Plate XLIII. fig. 4, m) lined by an inner 
(mucous ?) coat, the rugz of which are apparent while the wavy peristaltic action of the 
canal is going on from above downward during the passage of food. About the. 
posterior third of Firola (Plate XLIII. fig. 4, s), and behind the ventral fin, there 
exists a fusiform dilatation to about three times the diameter above and below; at 
the anterior orifice of which (s' the canal presented an evident constriction, obvi- 
ously meant to prevent return of food. At the lower or posterior end a second fold 
(s”) projected into the canal, which might be supposed to represent the pylorie, as 
the other did the cardiac valves of the human stomach. The bolus of food (not 
figured here, to make anatomical details clearer) contained in this cavity appeared 
to move about, not with a regular circulatory motion, as in the human subject, but to 
and fro from end to end, as if by peristaltic action alone, which impulse is thus propa- 
gated uninterruptedly along the whole length of the intestinal canal. A corresponding 
dilatation existed well in front in Firoloides (Plate XLIV. fig. 13). In other varieties (e. g. 
Firoloides, Plate XLIII. fig. 4) only one exists, viz. where the alimentary tube curves 
down and enters the visceral (pallial) division of the body, above and in front of the 
liver. This is probably the true stomach, and the enlargement observed in the above- . 
mentioned instances only accidental and caused by the passage of food—an opinion 
confirmed by the circumstance that it is into the posterior wall of the latter that the 
biliary duct yields its secretion. Behind the stomach a short intestine runs downward 
and backward to terminate in the vent (Plate XLIII. figs. 1, 4). The peristaltic action 
appears to be the only independent movement the stomach possesses; nor, from the 
nature of the food, which consists of animals with soft tissues identical with or very 
like their own, is any other needed, as little trituration is necessary, the solvent action 
of the salivary, gastric, and hepatic secretions being alone sufficient to prepare them for 
absorption. 
Two sets of glands appear subservient to digestion, viz. the salivary and liver. The 
former (Plate XLITI. figs. 2,8, 5, N), two in number, and comparatively large, lie under 
the buccal mass, curving downwards and backwards on either side of the cesophagus, 
and form elongated tubes, narrowing posteriorly, each having a central duct of large 
calibre, joined obliquely on each side by certain short and wide unbranched sacculi—a very 
simple glandular arrangement, the main duct of which opens into the buccal cavity 
well in front and beneath the tongue. As already described, these glands and the sense 
