THE r.KANCIIKHJASTKKOl'ODA. 



37 



are made good by the incessant development of new teeth in 

 the secreting sac in which the hinder end of the strap is Lodged. 

 Besides the chain-saw-like motion of the strap, the odontophore 

 may be capable of a licking or scraping action as a whole. 



Fig. 14. — Section ot a female whelk (Buccinum). The organs marked t and A are removed 

 from their proper places ; the others are seen in situ, a, mouth ; b, gullet ; c, head ; d , 

 foot ; e, operculum ; /, free part of the mantle ; g, that part which invests the 

 visceral mass lodged within the shell ; h, a gland of unknown function connected with 

 the gullet ; i, crop ; k, stomach ; /, intestine; m, rectum ; n, heart ; o, aperture of the 

 renal organ; r, mucous gland developed from the wall of the mantle cavity; s, 

 oviduct; t, salivary gland. The arrows indicate the position of the branchiae. The 

 cerebral, pedal, and parieto-splanchnic ganglia closely surround the gullet, and the 

 latter send off a long ganglionated cord towards the heart and branchiae. 



The other peculiarity of the alimentary canal of the 

 Branchiogasterojooda is that it is always bent upon itself, at first, 

 not to the neural, but to the haemal, or heart side of the body — 

 the rectum very commonly opening into the mantle cavity, 

 above the cephalic portion of the body. 



In most Branchiogasterojpoda the foot is a broad, flat, mus- 

 cular body, without any distinct division of parts ; but in some 

 forms, such, as the Heteropoda of Cuvier, it is divided into three 

 very well-marked portions — an anterior, a middle, and a pos- 

 terior, which are termed respectively the propodium, mesopo- 



