LIMAX MAXIM US LINN/EUS 225 



The lung is simply the modified inner surface of the mantle 

 cavity. It is oval, like the external surface of the shield, but 

 the rear third of it is occupied by the pericard with the heart, 

 the nephridium and part of the rectum. The rest of the surface 

 presents a network of fine blood-vessels, some of which are 

 arteries while others are veins. The pneumostoma or opening 

 leading into the pallial cavity may be closed or opened at will 

 by the action of a double sphincter. 



Nervous system and sense organs. The nervous system 

 of Limax, while considerably more complicated than that of the 

 lamellibranch Venus, still presents the characteristic paired gan- 

 glia. Above the oesophagus is the pair of cerebral ganglia united 

 to each other by a commissura cerebralis. Nine pairs of nerves 

 are given off by these ganglia to the various organs of the head; 

 of these the so-called buccal nerves form a pair of buccal ganglia 

 on the dorsal surface of the pharynx. A tenth nerve is given off 

 by the right cerebral ganglion to supply the penis. The posterior 

 region of each cerebral ganglion forms two lobes, the pedal 

 lobe lying more to the outside, and the visceral lobe more to the 

 inside. The pedal lobe of each side gives rise to a cerebropedal 

 connective. The two pedal ganglia lie under the cephalic artery. 

 Of the four pairs of pedal nerves arising from the two ganglia 

 the last pair is the longest and may be traced without difficulty 

 to the rear end of the foot beyond the visceral complex. The 

 visceral lobes of the cerebral ganglia give rise to a pair of cere- 

 bropleural connectives which end in the pleural ganglia of the 

 suboesophageal ganglionic mass. This mass, which lies below the 

 oesophagus, but above the cephalic artery, consists of five dis- 

 tinct ganglia. The outside pair is formed by the pleural ganglia, 

 then follows the pair of parietal ganglia and the centre is occupied 

 by a single visceral ganglion. The latter, however, must be re- 

 garded as the result of an early fusion of a pair of ganglia. The 

 subcesophageal ganglionic mass gives off nerves to the mantle, 

 lung and viscera. 



The senses are more or less highly developed. The whole in- 



