CHROMODORIS ZEBRA HEILPRIN 633 



tapers off into the large olfactory nerve, that passes into the base 

 of the rhinophore. Upon the dorsal surface, near the external 

 margin of the cerebral gangha, arise the two small optic gangha, 

 each of which sends a short nerve to the corresponding eye (oc). 

 Each cerebral ganglion gives rise to three pairs of nerves, which 

 pass forward and innervate respectively the oral tentacles, the 

 mouth, and the lips. Besides these nerves, each ganglion sends 

 from its mid- ventral surface a connective which passes around the 

 oesophagus to the buccal ganglia (gn.buc.) ; these lie, side by side, 

 ventral to the oesophagus just behind the buccal mass. A slender 

 nerve leads forward from each buccal ganglion to the tongue. 

 Two lateral nerves from each buccal ganglion innervate the buc- 

 cal mass. Posteriorly, a small ganghon (gn.oes.) is joined to each 

 buccal ganglion by an exceedingly short-nerve. This oesophageal 

 ganglion sends down the oesophagus a single nerve, which has 

 three branches that spread over the tube. 



Lying more dorsal and slightly posterior to the cerebral ganglia, 

 to which they are joined by very short connectives, are the equally 

 large pleural ganglia {gn.pl.). These generally give rise to three 

 pairs of nerves which innervate the mantle. From one of them 

 arises on the right side a slender nerve (n.vsc), which communi- 

 cates with the visceral part of the nervous system. 



The pedal ganglia (fig. 5, gn.pd.), not so closely united to the 

 others, lie in a more lateral position. From 4 to 5 pairs of nerves 

 arise from them. Of these, two pairs of the smaller nerves 

 innervate the body wall, while of the remaining larger ones at 

 least two pairs pass to the foot as anterior and posterior pedal 

 nerves. 



The pedal and pleural commissures {co' ms.pl. -\-pd.) unite into 

 a single broad band, which encircles the oesophagus ventrally, 

 the nerve fibers arising in each case from the posterior margin of 

 the ganglion. Two large nerves (xx.xy.), arising close to this 

 commissure, innervate the liver and genitalia. Their precise 

 origin is difficult to ascertain. The remaining pairs of nerves are 

 distributed posteriorly to the mantle. 



The study of the central nervous system of this nudibranch 

 brought out the fact that there is considerable variation in the total 



