PEARLY NAUTILUS. 



343 



osphiadium, viz. they are innervated by nerves arising from the 

 visceral commissure. 



I'lsc^ii: 



Fig. 2. — View of the postero-veutral surface of the body of a male Nau- 

 tilus pompilius, as seen wheu the mautle-skirt is reflected. The gills 

 aud the foot are cut short. Drawn from the object by Mr. A. G. Bourne, 

 and reduced to one half the natural diameter, a. Muscular baud from 

 the foot (siphon) to the body- wall. c. The reflected border of the mantle, 

 skirt. an. Anus. x. Peculiar median group of post-anal papillse of 

 unknown significance, j)^- Penis-like opening of the right sperm-duct. 

 /. sp. Aperture of the left sperm-duct. 7ieph. a., neph. p., vise, per., and 

 olf., as in Fig. 1. 



The nervous system of Nautihis is represented in fig. 3. In 

 the Cephalopoda, as in some other forms (most Pteropoda, some 

 Gastropoda), the visceral and pleural ganglia are not separated 

 from one another, but form a continuous nervous band (j)l. vise). 

 Nerves to the mantle (m.) proceed from the pleural portion of 

 this transverse baud, whilst a large visceral nerve {n. vise.) 

 proceeds from each of the contiguous visceral portions of the 

 same band, which represent the visceral ganglia. These large 

 visceral nerves give off each a genital ganglion {gen.) in the 

 neighbourhood of the genital ducts, and then, taking a super- 

 ficial course, divide each into two branches, one supplying the 

 anterior the other the posterior branchia of its side. 



