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central gullet; and the i ntestine. more or less bunt 14)011 i 

 ends in a medial. vent nil anus. 



One or two pairs of salivary glands are present in the dibrau- 

 ehiat.es. hut wanting in Nautilus. The liver is always large ; and 

 the two hepatic ducts a iv generally glandular. A large and 

 sometimes spirally-wound c;eeuni is frequently developed from 

 the eonnneneeinent of Ihe intestine, with which the hepatic ducts 

 commnnieate. The product of the salivary glands is uncolored, 

 limpid and acid, whilst that of the liver and pancreas is also un- 

 colored and acid, bill rarely limpid. 



In the betrabranchiata and the deca|)oda the (esophagus is 

 dilate<l into a crop separated from tin- stomach by a constriction. 

 The carnin is small and rounded, and the intestine i> twice bent 

 upon itself. The four-lobed loosely racemose liver is lodged in 

 the, anterior portion of the perivisceral cavity, and is largely 

 developed. From either side of it spring biliary ducts which 

 open in the large blind-sack; the pancreas is found at their 

 commencement. 



The Nervous Sy.-tein is mainly identical with that of the 

 gasteropods. There a i'e the three typical pairs, the cerebral. 

 pedal and visceral ganglia, surrounding the millet and connected 

 by commissures; whilst the nerves which supply the buccal 

 mass, the alimentary canal, the heart, the branchia 1 and the 

 mantle develop additional local jjanijlia. 



The dihraiichiates have the principal u'an^lia so closely con- 

 nected that the commissures are not readily perceived. The 

 optic nerves are well developed. 'The superior and inferior 

 buccal j^in^lia have each united in one mass, and the two are 

 united by commissures around the u'sopha^us. The lar^e nerves 

 of the arms, and those of the funnel or siphon, proceed from the 

 pedal jjanjrlia. which are placed on the posterior side of the 

 -iillet; with them are connected also the auditory nerves. From 

 the parieto-splaiichnic or visceral lian^lia proceed nerves ahnii; 

 the shell-muscles to tin- anterior wall of the mantle, where they 

 enter the lar^e ijinujliu uli-llutn ; these are connected by commis- 

 sures, and send strong cords to the tins. Branches of the 

 parieto-splanchnic i;an^lia, following- the vena-ca.va. supply the 



