18 



WALTER K. FISHER, 



Fig. G. Aperture of left reno-peri- 

 cardial canal into left kidney, very much 

 enlarged. 



Thus the two reno-pericardial canals open into, or are continuous 

 with a funnel-like dextrally directed diverticulum of the pericardium, 

 and do not open separately into the main triangular pericardial cavity. 



Furthermore it is evident that the 

 nephridial ends of these canals are 

 far removed from the pericardium 

 proper, and each opens, in re- 

 latively the same place, near 

 each ureter. 



These canals and openings I 

 have carefully examined also in Ac- 

 maea patina and A. spectrum. In 

 these species the reno-pericardial ducts hold the same relations as in 

 Lottia gigantea., and likewise the papillae are similarly situated in 

 each nephridium. In Acmaea spectrum the papillae are a trifle larger 

 in proportion to the size of the animal, than in Lottia. 



The Reproductive System. 



The gonad is situated beneath the alimentary canal and lies 

 (Fig. 1) in a special compartment which is probably a portion of the 

 secondary body cavity. During the breeding season (evidently about 

 midwinter) it is so enlarged as to much exceed in size the other 

 viscera. If these are stripped off, the gonad appears as in Fig. 23. 

 It is then seen to reach from the buccal sinus in front to the end of 

 the visceral cavity behind, and about its edge to extend upward 

 nearly or quite to the dorsal wall of the body. Thus the alimentary 

 canal seems to rest in a bowl-like hollow in the midst of the gonad. 

 Forward, the gonad is produced into three divisions, two ventral, 

 forwardly directed ones which encroach onto the head cavity, and a 

 dorsal process extending from left to right behind and under the 

 pericardium (Figs. 1, 20, 23). The end of this process is situated 

 beneath the mantle cavity between the aorta and rectum and is some- 

 times quite extended. The portion of the gonad shown in Fig. 20 is 

 merely the dorsal part of this process. The tip is well forward of 

 the left nephridium. From this tip a thin- walled tube difficult of 

 observation leads to the right and opens into the dorsal arm of the 

 sub anal portion of the right nephridium. This duct is lined with 

 coelomic epithelium, and doubtless when the sex products are being 

 shed could be more readily followed. The opening is more easily 

 seen as it appears to be ciliated, and possesses prominent lips. The 



