24 OPISTHOBRANCHIATA OF BRAZIL 



of this species in dorsal view, the abbreviations in the following 

 description all referring to this figure. The nerves are numbered 

 rather arbitrarily in the order of their origin from the ganglia, 

 from above and in front, downward and backward, the relative 

 peripheral distribution not being primarily considered in this 

 arrangement. 



Cerebral Nerves. The cerebral ganglia (cer. g.) are situated 

 upon the dorsal side of the esophagus at its anterior end, and are 

 so closely applied to each other that the cerebral commissures 

 connecting them are very short, the two ganglia being practically 

 fused together in the median line into a single mass. They are 

 rounded, and flattened upon their dorsal surface, and fit closely 

 down upon the underlying esophagus. From the sides of the 

 ganglia, close up to the origin of the fifth nerves, arise the strong 

 cerebro-buccal connectives, (c. b. con.), which curve downward, 

 around the esophagus, to the buccal ganglia. Below and behind 

 the origin of these arise the cerebro-pedal connectives, (c. p. con.), 

 which pass downward and outward to the large pedal ganglia, 

 (ped. g.), beneath the esophagus, and, close to the origin of the 

 latter pair, the equally stout cerebro-pleural connectives (c. pi. 

 con.) are given off. These pass downward, outward and back- 

 ward, and terminate in the small pleural ganglia (pi. g.), resting 

 upon the upper border of the pedal ganglia. 



From the cerebral ganglia arise six pairs of nerves, the 

 origin and distribution of which is the same for both sides, unless 

 otherwise noted in the following description. 



The first nerve (ci) is a strong one, arising from the anterior 

 border of the ganglion, passing forward over the pharyngeal 

 bulb, and is distributed to the skin and muscles in the region of the 

 mouth. 



The second nerve (02}, is broad and strong, arising imme- 

 diately behind the first. After a short course it bifurcates, its 

 more slender external division passing to the anterior tentacle, 

 and terminating in a small ganglion at its distal extremity. The 

 stout inner branch splits up into a number of smaller branches, 

 all terminating in the integument in the neighborhood of the 

 mouth. 



The third nerve (03), arises immediately behind the first, 

 but more dorsally. It is more slender, and passes to the rhino- 



