326 
THE OCEAN WORLD. 
The heart of the oyster is placed under the liver, and is surrounded 
closely by the terminal part of the intestines. It is composed, lik e 
the same organ in the superior animal, by two distinct cavities, a ® 
auricle and ventricle. From the ventricle issues a vessel, which ^ 
divided into three distinct canals. One of these carries the bloo 
towards the mouth and tentacles ; another carries it towards the liver , 
the List distributes the nourishing fluid to the rest of the body. T^ e 
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 spot e > 
which distributes it into the interior of the animal. 
The oyster thus possesses a true circulation ; not that double 
system which characterises the mammals, and which includes arteria 
and pulmonary action, but a simple circulation, as it exists in fishes 
and many other animals. It breathes also in the bottom of the water, 
after the manner of fishes, being, like the fish, provided with organ 3 
called gills or branchiae, whose function is to separate the oxygen di s ' 
solved in the water from its other ingredients ; these branchiae, whir 
are placed under the mantle, consist of a double series of very delic ate 
canals, placed close together, not unlike the teeth of a fine comb. 
Having no head, the oyster can have no brain ; the nerves original® 
near the mouth, where a great ganglion is visible, whence issues » 
pair of nerves which distribute themselves in the regions of th® 
stomach and liver, terminating in a second ganglion, situated hehi» l 
the liver. The first nervous branch distributes its sensibility to tb e 
mouth and tentacles ; the second, to the respiratory branchiae. 
With organs of the senses oysters are unprovided. Condemned 1° 
a sedentary life, riveted to a rock where they have been rooted, as d 
were, in their infancy, they neither see nor hear ; touch appears to b® 
their only sense, and that is placed in the tentacles of the mouth. 
The mode of reproduction in these creatures is very peculiar. ^h® 
oyster unites in itself the functions of both sexes. In the same org a ® 
are found the eggs — called spat , — and the mobile corpuscles intend^ 
to fertilize them. The oyster is hermaphrodite. 
The eggs are yellowish in colour, and exist in prodigious numbe 1 ' 3 
in each individual. We are assured that an oyster may carry as wa®? 
as two millions of eggs ! Nature always makes ample provision 
the preservation of species ; but in spite of the most ample provis® 3 ® 
