408 
THE OCEAN WORLD. 
(Fig. 203). Aplysia inca shows also the same arrangement (Fig. 201)- 
In this family the mollusc is much more important from its volume 
than from its internal, rudimentary, and horny shell, which is cow 
tained in the branchial shield. In Fig. 205 we have the small and 
thin cartilaginous shell, which exists in the interior of the animal. 
The Aplysim are found nearly in every region of the globe, not only 
upon the shores of the Continent, but on every island shore. They 
commonly inhabit sandy and muddy shores of small depths, or even 
the rocky recesses, or under shelter of the stones which have fallen 
from the cliffs. Their eggs consist of those long filaments which are 
discharged in immense numbers, and which fishermen call sea-worn^ 
They feed upon certain algae, with which the bottom of the sea lS 
Fig. 203. Aplysia depilan* 
(Limueus). 
Fig. 204. Aplysia inca (D'Orbigny). 
Fig. 205. Shell of 
Aplysia inca. 
covered; but they eat, also, small marine animals, such as the naked 
molluscs, annelids, and crustaceans. 
We are the less astonished to see the Aplysise so gluttonous when 
we learn how liberally Nature has accorded to them organs of mafl* 1 ' 
cation, trituration, and digestion. Their mouth is formed of thick 
and muscular lips; a very long oesophagus or gullet succeeds, nnd 
this oesophagus does not communicate with a single stomach, hw 
with four — one enormous membranous crop, an exceedingly musculo 
gizzard, with two accessary pockets, one of which terminates in th e 
form of a sac. The gizzard has thick walls, and is furnished on ( h G 
internal wall with cartilaginous quadrangular pyramids, the sutnniih 
of which intertwine. This apparatus is intended to bruise the fn° c 
when it reaches the third stomach. It is also armed with lit$ e 
hooks, the curvature of which is directed towards the entrance of 
