212 THE ORGANIZATION 



the gullet, called (he buccal nerves and ganglion, because they 

 supply the parts about the mouth. From behind the brain (g- 2 ) 

 three great nerves originate, namely, a single median and two 

 lateral. The single median one (og) arises from the upper 

 median lobe, and passes along the upper side of the liver, (lv,) and 

 branches to supply the various organs of the viscera. On this 

 account it is called the visceral nerve. The two lateral nerves (n) 

 originate from the pair of small lobes which lie on each side of 

 the great upper one, (g- 2 ,) and belong to a system which has 

 such complicated relations as to puzzle comparative anatomists 

 in regard to what they correspond with in the group to which the 

 Snail belongs. They are termed the mantle nerves; but as they 

 are also continued, on each side, to the extreme posterior end of 

 the body, and there supply the highly muscular fin, (/#,) in all 

 probability they correspond to the great foot-nerves of the Snail 

 (fig. 122, n, nir) ; and consequently the two small lobes from 

 which they arise, notwithstanding they are situated rather- above 

 the level of the throat, homologize with the widely separated 

 pair of ganglions, sub- cesohageal, (figs. 122, 123, ,) which lie at 

 the lower borders of the gullet of the Snail. 



The reproductive organ (figs. 124, 125, ov) is an oval or sphe- 

 roidal body, varying in size according to the season of the year, 

 which lies to the right of the first stomach (st). Its outlet, oviduct, 

 is a narrow canal which passes upward and forward, and opens 

 near the posterior end (an) of the intestine. 



The ink-bag lies close to the side of the posterior end of the 

 intestine, (at hv 1 ,) and opens near the aperture of the latter. 

 When alarmed, the animal beclouds the water about it by ex- 

 pelling the dark brown contents of this bag. 



The rudiment of a shell (*/t, sh l ) is imbedded in the thickness 

 of the mantle along the whole length of its lower middle line. 

 It consists of a semi-transparent, amber-colored, delicate, horn- 

 like substance, and has the shape of a straight sword-blade, 

 gradually widening toward the point; and at its posterior end is 

 fashioned into a hollow cone (sh l ) with the concavity facing Tor- 

 wards and obliquely upwards. In position it corresponds with 



