THE AN ATOM 3f OF DOKIS. 125 



oral tentacles, the lips, and the channel of the mouth. The 

 olfactory give their nerves to the dorsal tentacles, which we consider 

 as organs of smeU. The posterior, or branchial, ganglia distribute 

 nerves to the whole of the mantle, and a branch on each side to 

 the branchial sympathetic system. 



The lateral or pedial ganglia supply the foot. The visceral is 

 attached to the branchial ganglion of the right side, and sends off 

 four nerves, -which go to the sympathetic ganglia ©f the organs of 

 reproduction, the stomach, the hearts, and the branchia. The 

 cerebroids are connected with both pedial and branchial ganglia, 

 and these two last with each other. The cerebroids communicate 

 with each other acrosa the median line. There are three nervous 

 collars around the oesophagus ; the first passes from one cerebroid 

 ganglion to the other, the second from the same to the buceal ganglia 

 of the infra-oesophageal, the third is composed of three strands, two 

 of which pass from pedial to pedial ganglion, the third from the left 

 branchial to the visceral. The infra-oesophageal are two symme- 

 trical pairs, buccal and gastro-oesophageal. These give off six 

 pairs of nerves. The former ganglia supply nervous twigs to the 

 buccalmass and tongue, the latter to the salivary glands, oesophagus, 

 and stomach. The two chief nerves from these ganglia are applied 

 to the oesophagus, and these communicate freely with the oeso- 

 phageal sympathetic plexus, and terminate in ganglia of the 

 sympathetic system at the cardiac end of stomach. These are the 

 stomato-gastric nerves of previous authors, and correspond to the 

 gastric portions of the par vagum of the Vertebrata. 



There are twenty-one pairs of nerves, and four single nerves 

 given off from the above oesophageal ganglia. 



The sympathetic system exists, and is more or less demonstrable 

 in the skin, the buccal mass, and on all the internal organs. It 

 consists of a vast number of minute and distinct ganglia, varying 

 in size and form, the largest quite visible to the naked eye, of a 

 bright orange colour like the ganglia around the oesophagus, and 

 interconnected by numerous delicate, white, nervous filaments, 

 arranged in more or less open plexuses. This beautiful system 

 is connected, as already indicated, with both sets of oesophageal 

 ganglia. 



