118 



The first kind of cells, tliose lining the coelomoducts, 

 have been found in Lamellibranchs to contain Urea or 

 Uric Acid, whilst in Pectcn maximus the excretory cells 

 of the auricle have been found to contain Hippuric Acid 

 (18). In both cases the contents are extruded, in the 

 former into the cavity of the coelomoduct and in the 

 latter into the pericardium (at least by the cells of the 

 auricles), from \vhence they pass by the renal-pericardial 

 openings into the coelomoducts, and so outwards. 



Finally, there are granular eosinophilous cells, which 

 are found in numbers along the mantle edge. In places 

 they can be seen extruding their contents, and they 

 probably also perform some excretory function, though 

 since none are found in the connective tissue it is not easy 

 to determine their origin. 



EEPRODUCTIYE OEGANS. 



The genus Pecten is interesting because both 

 unisexual and hermaphrodite species exist. P. tenui- 

 costatus (Mighels), the giant scallop of America, is 

 unisexual. P. opercularis and P. maximus are both 

 hermaphrodite. In the two latter species the reproduc- 

 tive organs are posterior and ventral to the rudimentary 

 foot, forming a tongue-like mass attached to and 

 depending from the adductor muscle (fig. 1, Go. o. and 

 Go. s.). They do not extend into the mantle or encroach 

 upon other organs, even when expanded to their greatest 

 extent in the spawning season. 



When the sexual products are nearly ripe the organ 

 is at its largest, and is firm in consistency as if the 

 contents were pressing against their walls. At this lime 

 the male portion of the gland (fig. 1, Go. s.), which is 

 situated most dorsally and anteriorly, extends to a point 



