44 MUSSEL CULTURE 



as the posterior adductor muscle, where it curv^es 

 back upon itself, and returns in a somewhat 

 oblique manner to the left side of the stomach, 

 from which situation it finally passes back to 

 the anus. 



In Sabatier's description, the straight back- 

 ward portion, which I have described as the 

 first part of the intestine, is included as part of 

 the stomach (called the tubular stomach). 



The heart, consisting of a central ventricle and 

 two lateral auricles, is situated in a thin walled 

 cavity of its own, rather behind the middle point 

 in the line along the back of the mussel. A won- 

 derfully complete system of arteries and veins, 

 beautifully demonstrated by Sabatier, supply the 

 various organs. 



Two kidneys, or, as they are commonly called 

 in shell-fishes, the organ of Bojanus, are found on 

 the lower side of the body, one passing on each 

 side of the foot, brownish in colour, having open- 

 ings, as already noted, immediately behind the 

 genital papillae. Two internal openings also 

 communicate with the cavity in which the heart 

 is situated, and in this way the organ has a more 

 powerful action in aerating the blood. 



The nervous system shows three centres of 



