50 PHYSIOLOGICAL SERIES. 



centres, the other two between the pedal. The nerves from 

 tlu> pleural ganglia innervate the mantle ; one of those on 

 the right side is of largo si/e, and forms a considerable 

 ganglion before breaking up to innervate the penis, rectum. 

 and neighbouring parts. The pedal ganglia are continue. I 

 backwards in the substance of the foot as a pair of longi- 

 tudinal /?/>nms cords, connected together by 3 or 4 delicate 

 commissures. From their outer sides a number of pedal 

 nerves are given off, which towards the margin of the foot 

 form a rich plexus with minute ganglia at the meeting- 

 points of the nerve-filaments. The pedal system, except 

 for the absence of ganglion-cells in the longitudinal cords, 

 closely resembles the "ladder-like" system of Vivipara 

 [Paludina]. The cerebral ganglia are united by a long 

 ribbon-like commissure; they innervate the cephalic sense- 

 organs, and are united by a pair of long connectives to two 

 small buccal ganglia situated in the usual place on the 

 posterior surface of the buccal mass and connected by a 

 suboesophageal commissure. 0. 0. 1305 G. 



Burne, Proc. Malac. Soc., vol. iii. 1899, p. 317. 



D. 49. A Heteropod (Carinaria mediterranea) with the nervous 

 system displayed from the left side. The system, which is 

 very delicate compared with the size of the animal, bears 

 many resemblances to that of a Prosobranch. particularly 

 in the possession of a crossed (streptoneurous) visceral 

 loop. The ganglia are considerably lobulated. There are 

 two main pairs (i.) the cerebral (fig. 16), from \vhich 

 nerves are given off to the large and highly-organised eve-, 

 the otocyst, tentacles, and laliial region of the integument ; 

 and (ii.) the pedal ganglia. The latter lie above the tin 

 within the body ; each is bilobed, with the two lobes one 

 above and slightly in front of the other. The upper lobe 

 receives a stout connective from the cerebral ganglion, and 

 gives off from its hinder end a connective to the \i>e-ral 

 >glion of the same .-ide, and from its upper surface 

 3 or 4 tine nerves that radiate to the body- wall. A large 

 nerve for the penis rises from the upper lobe on the right 

 side. The lower lobe sends nerves to the body-wall and 

 to the various regions of the foot, that to the fin being 



