CELA PLE R XO, 
THE CEPHALOUS MOLLUSKS. 
HAVING considered the Acephalous Mollusks, which are headless, 
we now naturally proceed to the higher class, the Cephalous 
Mollusks, creatures which are endowed with the crowning member 
of the body. As in the lower class, so here we find some shell-less 
or naked, and others defended by a protective carapace. The nude 
cephalas exhibit much diversity of form ; they generally approach 
an oval, of greater or less length, convex above and flat underneath. 
Their head is at once recognised, for it is furnished with the 
sensitive organs or feelers, between which are situated two promi- 
nent, watery eyes; besides these, some of the species possess 
tentacles and feathery projections. A great gulf is fixed between 
these and the bivalves last considered, for they possess the power 
of locomotion; they can crawl. They execute this motion by 
means of a fleshy, abdominal projection, a kind of enlarged disc, 
which is formed by an interlacing of muscular fibres; by this organ 
the creature is enabled to execute a series of undulations which 
may be compared to the motion of a little wave. It was because 
of this ventral foot that Cuvier named the race the Gasteropods. 
First, we shall speak of the Afplysie—the sea-hares—little 
mollusks which have a fancied resemblance to the quadrupeds after 
which they are named. Their habitat is among marine plants; 
they have a long neck, and two hollow, horn-like protuberances, 
like the ears of a hare. Their teeth are not in the mouth, but in 
the stomach, which is quadruple. The first stomach is an enlarged 
crop, the next a kind of gizzard, the third a pouch, and the last 
a sac. The gizzard is constructed of several cartilaginous pyra- 
midal projections, whose edges are partly joined together so that 
their points are left separate. Several of these approach each 
other from each side of the organ, and their points are so close 
as to triturate the food as it passes through the second stomach. 
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