ORGANIZATION OF CERATOCEPHALE OSAWAI. 



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short distance from the points of their origin, the two nerves unite into 

 one which forms a part of the oesophageal ring. 



N X and N. XI. are the optic nerves. The former, arising from 

 the dorso-lateral aspect of the anterior cerebral lobe, supplies the anterior 

 eye of the same side The latter, which originates from the dorso- 

 lateral aspect of the fundus of the Literal notch between the anterior and 

 posterior cerebral lobes, goes to the posterior eye. 



N. XII , the last of the cerebral nerves, springs from the postero- 

 lateral margin of the posterior cerebral lobe. It ends in the ciliated groove 

 between the pnestomium and the buccal segment on the dorsal side. 



As the infra-cesophageal ganglion (fig S, / 0. g.) may be called the 

 anterior swollen end of the ventral nerve-cord, situated in the second body- 

 segment and just in front of the first ventral ganglion (i, e., the ganglion- 

 al swelling of the ventral nerve-cord in the second and third body- 

 segments). The infra-œsophageal ganglion presents an appearance bifur- 

 cated in the manner of the letter V, in that it is directly continuous in front 

 with the strong oesophageal connectives or commissures (ces. c). This 

 commissure, on each side, rounds the oesophagus and finally joins the 

 brain, thus completing the (esophageal ring, by means of two separate 

 branches or of the two cerebral nerves which I have called the VIII. and 

 the IX. (figs. 9 and 10). In the most lateral position of the ring and at 

 the base of the anterior tentacular cirri, the oesophageal commissure forms 

 a ganglional swelling which may be called the anterior cirrus ganglion 

 (fig. S, a e.g.). This ganglion sends off in front a nerve which proceeds 

 into the outer lateral wall of the protruded proboscis and behind it two 

 more nerves which innervate eacli for each the two (dorsal and ventral) 

 anterior tentacular cirri. Moreover, a short commissural nerve connects 

 the ganglion with the posterior cirrus ganglion situated just behind it. 

 About midway between the anterior cirrus ganglion and the infra-ceso- 

 phageal ganglion, the (esophageal connective gives off anteriorly a nerve 

 which goes into the outer ventral wall of the protruded proboscis. 



Directly behind the oesophageal connective, the infra-œsophageal 

 ganglion sends out on each side the so-called accessory oesophageal con- 



