NATURAL HISTORY OF THE MUSSEL 43 



ing mantle, being thus in the direct stream of 

 water passing along from the anterior to the 

 posterior end of the animal. If cut across, each 

 pair would be seen to be arranged in the form 

 of a narrow W, the central part of the letter 

 being the point of attachment, the outer and 

 inner arms (ascending lamellae) being free at 

 their upper ends. At the inner side of the point 

 of attachment, or central part of the W, near the 

 hinder end of the body proper of the mussel, 

 on each side, is the genital papilla, where the 

 eggs or sperms escape, and immediately behind 

 this again is the opening from the kidneys. Just 

 behind the muscle which closes the hinder part of 

 the shell the anus is situated, the rectum or last 

 part of the intestine being usually seen against 

 the light-coloured (posterior adductor) muscle. 



The digestive tract, from the mouth to the 

 anus, runs along what may be described as 

 the upper part of the shell below the hinge. 

 The gullet, which is simple, opens into an oval- 

 shaped stomach, the detailed arrangements of 

 which have given rise to some discussion among 

 zoologists, into which we need not here enter. 

 From the posterior end of the stomach the in- 

 testine passes backwards in a straight line as far 



