80 Transactions. 



exhibits two distinct portions — a small linear light area, which represenfe 

 the lens ; and a deeply pigmented region, surrounding this but for its 

 anterior end, is the retina (fig. 7). Below the eye, embedded in the sub- 

 stance of the tentacle, may be seen a mass of rounded particles of carbonate 

 of lime such as occur throughout the tissues of the body. 



Circulatory System. (Fig. 3.) 



The only portion of the circulatory system that needs describing is the 

 venous system. In order to trace out the veins I injected the animal 

 through the foot. The best results were obtained with glycerine carmine, 

 and the kidney was invariably well injected. 



The blood is collected into sinuses, as can be proved by thus injecting 

 the animal. From the larger sinuses the blood passes into two main tubular 

 sinuses or veins, the anterior sinus and the rectal sinus (fig. 3). 



On the left side the blood from the body enters the anterior sinus {as), 

 which lies along the collar. Shortly before reaching the pulmonary aper- 

 ture it curves round to connect with the pulmonary vein {pv), which runs 

 close beside the kidney, to enter the anterior end of the auricle. The 

 anterior sinus gives afferent branches to the lung {I) along its whole course, 

 and the blood is collected by efferent branches which enter the pulmonary 

 vein. Thus, though some of the blood enters the pulmonary vein directly 

 from the anterior sinus, most of it reaches the heart only after filtering 

 through the vessels of the mantle-roof, which constitutes the lung. 



The rectal sinus consists of two superposed channels, one above the 

 other — the inferior rectal sinus {irs) and the superior rectal sinus {srs). The 

 inferior rectal sinus commences at the inferior pallial lobe, and runs along 

 the floor of the mantle on the right side of and close to the rectum. It 

 extends back as far as the coils of the intestine, where it leaves the body- 

 waU floor of the mantle-chamber and, bending abruptly on itself, passes 

 forward along the roof of the mantle above its former course as the superior 

 rectal sinus [srs) as far as the pulmonary aperture. It then bends at right 

 angles and traverses the mantle as far as the commencement of the collar, 

 where it seems to cease. The blood, which enters both ends of the rectal 

 sinus, is carried through vessels traversing the mantle from the sinus to the 

 afferent renal vein, which runs along the dorsal surface of the kidney, and 

 which is therefore not shown in the drawing. The blood from the afferent 

 renal vein is then distributed through the sinuses in the connective tissue 

 which supports the filiform papillae of the kidney. These trabeculae of 

 connective tissue are traversed by axial sinuses which function as blood- 

 spaces. The blood thus reaches the efferent renal vein, which runs back- 

 wards near the ventral surface of the kidney, below the muscle-band, to 

 enter the auricle. 



I have had great difficulty in tracing out the circulatory system. The 

 heart and blood-vessels have such extremely thin walls that it is impossible 

 to inject them from the heart. On one occasion the injection went from 

 the auricle along the pulmonary vein and into the anterior sinus directly 

 for a short distance, but I did not observe any injection on the wall of the 

 lung itself. By injecting through the foot the kidney was invariably 

 well injected, and sections across the lung showed that the vessels of the 

 lung had also been injected. As explained above, the afferent and efferent 

 'vessels on the wall of the lung are not as clearly visible in Amphibola as 

 in Helix and in other pulmonates. The same is true of the vessels running 



