Introduclion to A nimal Morphology . 321 



buccal, four (Histioteuthis, Ommastrephes), or six (Sepia, 

 Loligo), or anal (one pair at the base of the funnel), as in 

 Philonexis, Ommastrephes, and Onychoteuthis ; sometimes 

 there are brachial pores at the base of the arms. Water 

 also enters the perivisceral cavity, which here, as in other 

 molluscs, acts as a large circulatory lacuna. 



The cerebral, pedal, and visceral pairs of ganglia 

 are close together, united by short commissures, or 

 even coalescent. The pharyngeal ring is protected 

 partly by the cartilage, and its investment is com- 

 pleted by a membranous sheath.* 



The pedal ganglia in Nautilus give off branches which 

 form a tentacular ganglion. In Dibranchs the corresponding 

 nerves often unite into a common trunk. On each side of 

 the mantle cavity on the viuscuhis lateralis is a large ganglion 

 stellatuvi connected with the visceral ganglion by commissures, 

 and distributing branches to the mantle. From the cerebral 

 ganglion arises a commissural band, which forms above the 

 oesophagus an upper buccal ganglion, and ventrally below an 

 inferior buccal, to which the sympathetic nerves are attached, 

 two long stems running along the oesophagus, and forming 

 a stomach ganglion, or pair of ganglia, giving branches to 

 the other viscera. Two stems attached to the hypopharyngeal 

 ganglion pass along the large venous trunks, and unite in a 

 pair of branchial ganglia at the base of the gills, joined by a 

 commissure. 



The sense of touch is seated chiefly in the tentacles, 

 taste in the before described pre-lingual papilla (or in 

 similar organs in Nautilus). The organ of smell may 

 be a short, trigonal, ciliated, hollow process, like the 

 sheath of a tentacle (Nautilus) placed below the eye, 



* This sheath is more complete in Dibranchs, in which the nerves often 

 pierce through the cartilage to their destination. The intravaginal space 

 is not filled by the nerve centres, but contains a fluid or a glandular (?) 

 mass. 



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