364 THE OCEAN WORLD. 



a level witli 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 mass of 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 intestines open in the 



The heart of the oyster is placed under the liver, and is surrounded 

 closely by the terminal part of the intestines. It is composed, like 

 the same organ in the superior animal, 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 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 into 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 in the bottom of the water, 

 after the manner of fishes, being, like the fish, provided with organs 

 called gills or Iranchite, whose function is to separate the oxygen dis- 

 solved in the water from its other ingredients ; these branchiae, which 

 are placed under the mantle, 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 to the 

 mouth and tentacles ; the second, to the respiratory branchiae. 



With organs of the senses oysters are unprovided. Condemned to 

 a sedentary life, riveted to a rock where they have been rooted, as it 

 were, in their infancy, they neither see nor hear; touch appears 



