342 Prof. F. W. Hutton on the Structare and 



stomach, wliicli is of a yellowish-white colour. The liver is 

 large and pale yellow ; the hepatic ducts open into the fundus 

 of the stomach. The intestine leaves the stomach abruptly 

 on the left side, and passes straight forward to the heart; 

 after passing round the aorta, it crosses obliquely backward 

 over the stomach to the right ; after making another short bend 

 forward and to the left, it bends once more backward and to 

 the left, descends as far as the end of the stomach, and then 

 passes straight to the anus, which lies in the lobe of the pul- 

 monary opening. Numerous particles of calcite are scattered 

 about the various organs. 



Re2)roductive System (figs. 2 and 7). — The ovo-testis is 

 rounded, like that oi' Limax, and of a brownish-yellow colour ; 

 the hermaphrodite duct is rather short and blackish. The 

 albumen-gland is short and of a pale yellow colour, like the 

 swollen portion of the oviduct. The spermatheca is brownish 

 or purplish, oval in shape, and with a long stalk. The vas 

 deferens leaves the oviduct near the anterior end of the 

 swollen portion. The oviduct is suddenly narrowed; and this 

 narrowest portion, together with the vas deferens and the 

 stalk of the spermatheca, penetrate into the musculature of 

 the foot ; they then turn sharply forward, and open with the 

 penis in a common genital opening on the right side of the 

 head. The penis is narrow and curved, and has a large pale 

 yellow gland for the secretion of the spermatophore. The 

 spermatophores (fig. 7) are long and cylindrical, rounded at 

 one end, and rather suddenly narrowed into a long tail at the 

 other. They are quite smooth. 



The renal organ (hgs. 3 and 4, d) is double, one half being- 

 attached to the lower, the other to the upper wall of the respi- 

 ratory chamber, in such a position that the one half lies over 

 the other. It lies on the left side of the animal ; and imme- 

 diately at its apex is situated the heart. 



Transversely across the animal, from the renal organ to 

 the respiratory opening, lie the gills (figs. 3 and 4, e). There 

 are two of them, attached, like the renal organ, to the upper 

 and lower surfaces of the respiratory chamber ; but the lower 

 one is very feebly developed. These gills are not free, but 

 are merely folds of the integument crossing between two large 

 vessels in the walls of the respiratory chamber. Evidently 

 they are adaptive in origin, and not homologous with the gills 

 of other MoUusca. The interior of the respiratory chamber, 

 and the gills, are richly ciliated ; and the animal seems to 

 respire air and water indifferently. The respiratory orifice is 

 often seen open, both in the air and under water ; but in the 

 latter case the lobe below the opening is generally raised, 



