198 SUPPLEMENT 
to say, formed on each side of a single salivary gland, which 
commencing more or less behind, on the sides of the intes- 
tinal canal, or even placed free in the visceral cavity, tra- 
verses the nervous ring, to open into a part of the buccal 
aperture. Sometimes the salivary apparatus is composed of 
two glands on each side, one disposed like that which we 
have just described, and the other filiform, and often ex- 
tended very far along the intestinal canal. The cones have 
one very singularly formed, unequal, situated in the visceral 
cavity, and of which the excretory duct, very long and re- 
entering, proceeds to open at the base of the tongue. 
The union of organs of which we have just spoken consti- 
tutes a mass more or less considerable, ordinarily oval, which 
is sometimes perceptible through the skin, but most frequently 
indistinct. ‘This buccal mass is surrounded by a great 
number of muscles, which can draw it forward, carry it back, 
and sometimes make the lower part act upon the upper. 
No indication of this is found in the acephala ; it is, on the 
contrary, very strong in most of the cephalophora, especially 
where there is a true mastication. 
It is almost always at the superior and posterior part of 
this mass that the intestinal canal, properly so called, com- 
mences with an cesophagus, whose diameter is always more 
narrow than its own. 
The intestinal canal of the mollusca, taken generally, is 
composed of an internal mucous membrane, most usually 
forming longitudinal folds, and of a muscular stratum more 
or less distinct, but evidently contractile in all its points. Its 
extent, its stomachal swellings, its direction, and its circum- 
volutions seem to present a great number of variations. 
Thus we sometimes find an cesophagus long and narrow as 
far as the stomach, or an cesophagus very broad, very large, 
as in most of the phytophagous mollusca. We also see, 
