48 PHYSIOLOGICAL SERIES. 



and always bears in its different, parts a definite relation to 

 the gut. The arm of the visceral loop that rises from the 

 left pleural ganglion passes beneath the gut to the opposite 

 side of the body ; here, at a point slightly posterior to the 

 free tip of the gill, it forms a ganglion (subintestinal 

 ganglion) from which the gill and olfactory organ (osphra- 

 dinm) are innervated. The loop continues its course round 

 the margin of the mantle-cavity, and at its hindennost 

 extremity forms another ganglion (abdominal ganglion), 

 from which several nerves are given off to the viscera. 

 On the left side of the mantle-cavity, opposite the sub- 

 intestinal ganglion, a third ganglion (supraintestiiml) is 

 formed for the innervation of the left gill and ospbradium. 

 After leaving this ganglion the loop turns to the right over 

 the dorsal surface of the intestine, and finally enters the 

 right pleural ganglion. 



Nerves are given off from the cerebral ganglia to the 

 sense-organs and integument of the head ; those to the lips 

 take their origin, in common with the buccal connectives, 

 from a prominence on the antero-ventral surface of ea< -h 

 ganglion (labial lobe). The buccal ganglia form a single 

 horseshoe-shaped band, situated on the posterior wall of the 

 buccal mass between the radular sac and oesophagus. 



0. C. 1305 F. 



Lacaze-Duthiers, Ann. Sci. Nat., se>. 4, t. xii. 

 p. 247. 



D. 47. The nervous system of a Limpet (Patella 



i-olated. This nervous system agrees in its general feature- 

 with that of Jfalioth, but differs from it in the following 

 important partieulars : The ganglia are more pronounced 

 and independent : this difference is particularly marked in 

 the separation of the pleural and pedal ganglia. The pedal 

 cords are not I'u-ed at their anterior end, but form a pair 

 of ganglionic enlargements united by a stout conmii ure. 

 Posteriorly they gradually become purely fibrous. The 

 pedal cords are united by two commit lire- only. The 

 labial lobes are detached from the cerebral ganglia. A 

 nerve of some length is interposed between the sub- and 

 supraintestinal ganglia and the visceral loop. 0. C. 1305 E. 



