The Canadian Oyster. 149 



empty their contents, and following the stomach is a 

 coiled intestine opening by an anus situated posteriorly 

 above the gills. The so-called liver really secretes the 

 digestive juice; and the Oyster has an amazingly good 

 digestion, for its rate of growth is astonishing. At the 

 end of the first year of its life it is about an inch in 

 length, at the close of the second year it has reached 

 between two and three inches, whilst in five years it 

 may attain a length of five to six inches. 



The organs by means of which the Oyster creates 

 the current which brings it its food are, as already 

 mentioned, the gills and the palps. The first-named 

 are familiary known as the " beard " of the Oyster, 

 they each consist of a lone 1 axis fringed on each side 

 with a number of filaments hanging down parallel to 

 one another, and all thickly clothed with cilia. The 

 ends of these filaments are turned up and fastened to 

 the mantel-lobes in the case of the outer ones, and to 

 the corresponding filaments of the other gill in the 

 case of the inner ones. In most Lamellibranchiata the 

 filaments of one row are welded together so as to form 

 a coherent plate or lamelle, from which circumstance in- 

 deed the term " lamelle-brandicate " is derived, but in the 

 Oyster the filaments of the same row cohere only by means 

 of the entanglement of their cilia, so that a touch is all that 

 is necessary to disengage them and hence the comparison 

 of the gill to a frill of hairs or beard. The palps are 

 two pairs of triangular folds situated one pair above and 

 the other below the mouth; they are furrowed by a 

 large number of parallel grooves lined with cilia. It 

 used to be supposed that their purpose was to direct 

 the current of water into the mouth, but it is now 

 known that their chief purpose is to remove the sur- 

 plus food that the Oyster cannot swallow. Even the 

 appetite of the Oyster it would seem has its limits. 



Situated in front of the adductor muscle is a cavity 

 covered on each side with a thin membrane, which is 

 generally torn in carelessly opening the Oyster. This 

 cavity is the body-cavity or pericardium of the animal, 

 and contains the heart. This organ consists of a single 

 pear-shaped ventricle above, from which arises an 



