10 EXPEEI^rEXTS IN THE BREEDING OF CERIONS. 



to the mantle collar without perceptible branching in any of the 

 species. The kidney lies just to the right of the pericardium and is 

 somewhat pointed anteriorly. It appears as a hollow sack of Ught- 

 grajdsh color, showing the glandular tissue hanging in irregular folds. 

 The kidney is attached to the dorsal wall of the pulmonajy ca^dty and 

 the ureter, joining the latter at the posterior end. The ureter bends 

 to the left as it passes forward, following the ventral side of the intestine 

 to the nephridiopore, which is near the anus. 



Considerable difference is shown in the genitalia of the several species 

 examined. Cerion incanum, Cerion casdblancoe, and Cerion uva in the 

 main agree with the description of Cerion munia chrysalis as described 

 by PUsbry in the Manual of Conchology. Cerion crassildbris and 

 Cerion viaregis, however, are decidedly different. The terminal element 

 of the system is formed by the atrium. This is broad and capacious in 

 Cerion incanum and Cerion casablancce, and less so in Cerion uva. In 

 Cerion crassilahris and Cerion viaregis it is much larger and much more 

 attenuated than in the rest. In Cerion incanum and Cerion casablancce 

 it is provided with a fleshy protuberance and some longitudinal folds 

 which are evertible in copulation. 



The penis is attached to the right side of the atrium and differs 

 considerably in shape and length in the species examined. In Cerion 

 incanum and Cerion casablancce it tapers to the upper end. In Cerion 

 uva it is bulbous at the upper end, while in Cerion crassilahris its shape 

 is more or less cyUndrical. In Cerion viaregis it is larger at the upper 

 end than in any of the other forms. The retractor muscle is attached 

 to the upper end of the penis sack in every case and is inserted not 

 far back on the floor of the pulmonar\- ca-\-ity. In Cerion incanum and 

 Cerion casablancce the vas deferens is attached to the lower end of the 

 penis. Its walls are densely muscular proximalh', while distally it 

 develops into a much coiled duct. The lower end has a silky appear- 

 ance which seems to be due to the circular fibers in its structure. In 

 Cerion uva the insertion of the vas deferens is at the upper end of the 

 penis sack, while in Cerion crassiJabris it is at about its center. These 

 two species have the duct doubled back and attached to the vagina for 

 its full length by muscle fibers. This is particularly so at the junction 

 of the vagina with the atrium. In Cerion viaregis the vas deferens is 

 attached to the upper end of the penis sack, but in a different manner 

 than in the other forms examined. The attachment to the vagina in 

 this form is less firm than in the others. (The figures of the genitjilia 

 in oiu- plates show the organs disentangled in order to bring out details.) 

 In Cerion incanum, Cerion casablancce, and Cerion crassilabris the vas 

 deferens is attached high up on the genital system, far above the 

 attachment of the spermatic duct. In Cerion uva it is attached about 

 halfway as high up on the vagma as it is in the species just mentioned 

 while in Cerion viaregis it enters the vagina far below the attachment 



