JO Elementary Zoology. 



stomach. From the stomach arises an intestine which, after 

 two or three turns, becomes the straight rectum leading to the 

 anal orifice. The alimentary canal of the snail is well supplied 

 with glands. There are, first of all, the salivary glands, one 

 on either side of the crop. From each a fine duct passes 

 forwards, and opens into the buccal mass just at its junction 

 with the oesophagus. The liver is a four-lobed brown mass, 

 occupying a great portion of the visceral mass, lying within 

 the visceral hump. Its ducts open into the stomach. 



The heart has one auricle and ventricle. Into the auricle 

 is poured the blood derived from the numerous vessels which 

 ramify over the surface of the mantle. From the ventricle 

 arises an artery, which subsequently divides and supplies the 

 body generally. The blood is faintly blue when exposed to 

 the atmosphere, the blue colour being due to a respiratory 

 pigment (haencyanin), analogous in its oxygen-carrying powers 

 to hjemoglobin, but of a different chemical composition. Its 

 metallic basis is copper instead of iron. The blood contains 

 colourless amoeboid corpuscles. The renal organ is single ; it 

 corresponds to one of two organs of Bojanus of the fresh-water 

 mussel. It opens, as already said, into the pericardium 

 ( = coelom) on the one hand, and on to the exterior, within the 

 mantle cavity, on the other. 



The nervous system is constituted quite upon the plan of 

 that of Anodon. The ganglia, however, are more crowded 

 together. The cerebral ganglia lie above the oesopTiagus, and 

 give off each of them a nerve which ends in a small buccal 

 ganglion, lying upon the buccal mass, and innervating it. 

 Connected with the cerebral ganglia by commissures passing 

 round the oesophagus are the pedal ganglia. On the pedal 

 ganglia lie the small auditory sacs ; but although these lie 

 upon the pedal ganglia, their supply-nerves come from the 

 cerebral. Behind the pedal ganglia are the chlamydo-splanchnic, 

 also connected by commissures with the cerebral. 



As is generally the case with hermaphrodite animals (cf. 

 the earthworm), the organs of reproduction are excessively 

 complicated. The essential part of the generative system is 

 the hermaphrodite gland, or ovo-tesiis, which produces both 



