374 THE OCEAN WORLD. 
flat triangular lips, by means of which the animal introduces its food 
into the stomachal cavity. 
A very short gullet is attached to the mouth, which leads to a 
pear-shaped stomach. After this stomach comes a slender sinuous 
intestine, which, leading obliquely towards the interior, descends a 
little, then re-ascends, passes behind the stomachal cavity, nearly on 
a level with the mouth, crossing its first path in order to reach the 
posterior face of the adductor muscle, in the centre of which it 
terminates with a free opening. The stomach and intestines are 
surrounded on all sides by the liver, which alone constitutes a notable 
portion of the total mass of the organs. This liver is of a blackish 
colour, pervaded with a deep yellow liquid, which is the bile. Thus, 
the stomach and intestines of the oyster are surrounded by the liver ; 
the mouth is connected with the stomach, and the intestinal canal 
has an opening of its own. 
The heart of the oyster is placed under the liver, and is sur- 
rounded closely by the terminal part of the intestines. It is com- 
posed, like the same organ in the superior animals, of two distinct 
cavities, an auricle and ventricle. From the ventricle issues a vessel, 
which is divided into three distinct canals. One of these carries the 
blood towards the mouth and labial tentacles: another carries it 
towards the liver ; the last distributes the nourishing fluid to the rest 
of the body. The blood of the oyster is limpid and colourless ; it 
passes successively from the auricle of the heart, where it is vivified, 
into the ventricle, and from this last cavity into the great vessel of 
which we spoke, which distributes it throughout the interior of the 
animal. 
The oyster thus possesses a true circulation; not that double 
system which characterises the mammals, and which includes arterial 
and pulmonary action, but a simple circulation, as it’ exists in fishes 
and many other animals. It breathes also under the water, after the 
manner of fishes, being, like the fish, provided with organs called 
gills or ranchie, whose function is to separate the oxvgen dissolved 
in the water from its other ingredients; these branchize, which are 
placed between the mantle folds, consist of a double series of very 
delicate canals, placed close together, not unlike the teeth of a fine 
comb. 
Having no head, the oyster can have no brain; the nerves 
originate near the mouth, where a great ganglion is visible, whence 
issues a pair of nerves which distribute themselves in the regions of 
the stomach and liver, terminating in a second ganglion, situated 
behind the liver. The first nervous branch distributes its sensibility 
