MOLLUSCS. 759 
(Helix, Limax), or at the side of it two jaws are found. The 
intestinal canal has various lengths, but is usually tortuous and 
longer than the body; it is very long, for instance, in Chiton and 
Patella, and makes many convolutions which are straitly enclosed by 
the liver. The cesophagus is sometimes expanded at the lower end 
like a crop, as in Limneeus, Planorbis, Nautilus and Octopus, which 
has longitudinal folds like those usually occurring in the cesopha- 
gus. The stomach is in some, as in Hel‘x, membranous, in others 
muscular. In many this muscular stomach is armed internally 
with hard parts, as in Scyllea, Bulla, Bullea, or the inner mem- 
brane is horny, as in Tethys and the Cephalopoda, just as it is in 
gallinaceous birds. There are often found pieces of Crustacea in this 
stomach, whence it may be concluded that a hard covering of this 
kind is serviceable for crushing hard food. In some the stomach 
is compound, as in Onchidium and Aplysia, in which three (or 
in the last named genus, according to CUVIER, even four) stomachs 
are present. The first stomach is here membranous, the second 
muscular, armed internally with larger cartilaginous teeth placed in 
circles alternately, and with a single row of smaller teeth at the 
upper edge; the third stomach is armed on its imner surface with 
hooks which are curved forwards; the fourth, finally, is an elongated 
blind sac, which is surrounded by the liver. According to OwEn, 
this blind sac may be a secreting organ, a pancreas in the simplest 
form, corresponding to the ccecal appendages at the inferior orifice 
of the stomach in fishes!. As such also he regards the so-called 
second stomach in the Cephalopods, a membranous blind appendage 
behind the muscular stomach, which in Sepia and Octopus incloses 
a spiral membranous valve, and in Nautilus is parted into many 
chambers by thin transverse membranous valves’, The termina- 
tion of the rectum in molluscs is usually situated on the right 
side of the body, always in the neighbourhood of the respiratory 
organs. 
Salivary glands, which are wanting in the preceding class, 
appear very constantly to be present in this. Commonly there are 
1 Lectures on the compar, Anat. of the invert. Anim, p. 300; sec. ed. p. 557. 
2 In some cephalopods there are folliculi, larger than the liver itself, which are 
attached to the gall-ducts; Hunrer regarded these as pancreas (Physiol. Catalogue I, 
p- 229), in which opinion V. S1EBOLD also participates. Lehrb. der vergl. Anat. 
8. 393- 
