298 ELEMENTARY BIOLOGY. [CHAP. 



a. The buccal 7ierves. That of the right side will 

 alone be seen ; it arises from the supra-oesophageal 

 ganglion, and passes downwards and forwards to- 

 wards the buccal mass. Trace it with care — ij 

 passes beneath the dorsal protractor muscle (see 

 Sect. E. I b), and terminates in a small buccal 

 ga7tglton, lying just behind the enlarged base of th 

 salivary-duct. 



M 



ii 



Just before it reaches the muscle referred to, it 

 usually gives off two or three branches to the 

 antero-lateral wall of the buccal-mass. H 



b. The anterior visceral nerves ; a system of fibres 

 arising from the above ganglion. The following 

 can be seen with ease. 



a. A ventral branch, distributed to the oesophagus.) 



^. A dorsal one, to the salivary gland, the due 

 of which it accompanies. 



y. An anterior one, to the roof of the buccs 

 mass. 



Remove the whole nervous system, together with the 

 buccal-mass and tentacle-bearing portion of the 

 cephalic integument. Pin down under water with 

 its posterior end uppermost, and dissect off as much 

 as possible of the sheath of the nerve-collar. Note, 

 in addition to the nerves already dissected — 



a. The buccal commissure; a delicate tract of nerve- 

 fibres, seen, on raising the cut end of the ceso- 

 phagus, to connect the buccal ganglia of opposite 

 sides. It, passes beneath the gullet. 



