80 
COMPARATIVE ZOOLOGY. 
the intestines end in a large bladder-like expansion. Scor* 
pions have no stomachal cavity—a straight intestine passes 
directly through the body. 
In bivalve Mollusks, like the Clam, the mouth opens 
into a short oesophagus which leads into the stomach, 
which lies imbedded in a large liver, and the intestine, 
describing a few turns, passes directly through the heart. 40 
In the univalve Mollusks, like the Snail, the gullet is long, 
and frequently expands into a crop; the stomach is often 
double, the anterior being a gizzard provided with teeth 
for mastication ; the intestine passes through the liver, 
and ends in the fore-part of the body, usually on the right 
side. 
The highest Mollusks, as the Cuttle-fish and Nautilus, 
exhibit a marked advance. A mouth with powerful man¬ 
dibles leads to a long gullet, which ends in a strong mus¬ 
cular gizzard resembling that of a fowl. 41 Below this is a 
cavity, which is either a stomach or duodenum ; it receives 
the secretion from 
a large digestive 
gland or pancreas. 
The intestine is a 
tube of uniform 
size, which, after 
one or two slight 
curves, bends up, 
and opens into the 
“funnel 55 near the 
mouth. 
Fishes have a 
simple, short, and 
wide alimentary 
Fig. 44. —Alimentary Canal of the Oyster: a, stomach canal. The StO in¬ 
laid open ; d, liver; b, c , d,f, convolutions of the intes- . 
tine, g, anal aperture; n, o, auricle and ventricle; I , ach Is Separated 
m, adductor muscle; h, k, lobes of mouth divided to r f i • f 
show the venous canals at the base of the gills. iioui Lite nil fount. 
