MOLLUSCA. 
6 
side, resembling a highly complicated fern leaf ; the great vena cava, 
having arrived between them, divides into two branches, which 
pour their contents into two fleshy ventricles, each of Avhich is 
placed at the base of the branchiae on its own side, and propels the 
blood into it. 
The two branchial veins communicate with a third ventricle, 
situated near the bottom of the sac, which, by means of various 
arteries, distributes the blood to every part of the body. 
Resi-)iration is effected by the water which flows into the sac and 
issues through the funnel. It appears that it can ev'^en penetrate into 
two cavities of the peritoneum, traversed by the vena cava in their 
passage to the branchiae, and act upon the venous blood by means of 
a glandular apparatus attached to those veins. 
Between the bases of the feet we find the mouth armed Avith two 
stout horny jaws, resembling the beak of a parrot. 
Between the two jaws is a tongue bristling with horny points ; the 
oesophagus swells into a crop, and then communicates with a gizzard 
as fleshy as that of a bird, to which succeeds a third membranous and 
spiral stomach, which receives the llTle from the two ducts of the very 
large liver. The intestine is . simjAe and short. The rectum termi- 
nates in the funnel. 
These animals are remarkable for a peculiar and intensely black 
excretion, with which they darken the surrounding Avater AA'hen they 
wisly'to conceal themselves. It is produced by a gland, and retained 
in a sac, variously situated, according to the species. 
Their brain, AAdiich is contained in a cartilaginous cavity of the 
head, gives off a cord on each side AA'hich produces a large ganglion 
in each orbit, Avhence are derived innumerable optic filaments ; the 
eye consists of several membranes, and is covered by the skin Avhich 
becomes diaphanous in that particular spot, sometimes forming folds 
Avhich supply the Avant of eyelids. The ear is merely a slight cavity, 
on each side near the brain, Avithout semicircular canals or an exter- 
nal meatus, Avhere a membranous sac is suspended AA^hich contains a 
little stone. 
Tlie skin of these animals, of the Octopi particularly, changes 
colour in places, by spots, Avith a rajildity Avhich greatly surpasses 
that of the cameleon.* 
The sexes are separated. The ovary of the female is in the bottom 
of the sac : tAVO oviducts take up the ova and pass them out through 
* See Carus, Nov. Act. Nat. Cur., XII., part I, p. 320, and Sangiovanni, Ann. 
des Sc. Nat. XVI, p. 308. 
