32 OPISTHOBRANCHIATA OF BRAZIL 



regarded as a salivary branch of the sixth, as it is distributed 

 to the sahvary gland, and thus would correspond to the branch 

 shown by Mazzarelli in the Neapolitan forms as arising well up 

 from the base of that nerve. 



The sixth nerve is a strong and important one. It cor- 

 responds to No. Ill of Mazzarelli's text, and to No. 4 of his fig. 9, 

 tav. IV. It is shown in figs. 9, 10 and ii, of PI. Ill as arising 

 from the posterior margin of the buccal ganglion, and bifurcating 

 after a short course. Its anterior division soon gives off a median 

 branch which breaks up in the wall of the esophagus, while the 

 remainder continues forward between that organ and the salivary 

 gland, giving off slender branches to each, and is finally dis- 

 tributed to the roof of the pharyngeal cavity at the beginning of 

 the esophagus. The posterior division of the sixth nerve forms 

 the esophageo-gastric nerve of each side. It courses backward 

 along the esophagus, over the ingluvies, giving oflf fine branches 

 at intervals to its walls. At the anterior boundary of the first 

 triturating stomach these two main lateral trunks, together with 

 several of their branches, unite in a circular plexus of fibres 

 around the anterior margin of this division of the stomach. From 

 this plexus, in which no ganglionic enlargements were found, 

 nerves pass into the wall, of the digestive tube, and several (six 

 or more) branches course backward to the second triturating 

 stomach, in the wall of which they branch and anastomose ir- 

 regularly, and thence are continued further back along the intes- 

 tinal tract in a similar manner. 



Parieto-visceral ganglia. The position of the parieto- visceral 

 ganglia, the "deuto-visceral ganglia" of Mazzarelli ('92) has been 

 mentioned above in connection with the pleural ganglia. The 

 two ganglia (PI. Ill, fig. 14), are completely fused together, 

 forming a pear shaped mass, and show indications of their double 

 nature at their anterior end alone, at the entrance of the two 

 connectives. The right, or pleural ganglion is uppermost, lying 

 directly above the left, or visceral ganglia. From them are given 

 off the following important nerves. 



Visceral nerves. From the left visceral ganglion arise three 

 nerves. The first of these (/. v. i), is the smallest. It originates 

 from the postero-dorsal side of the ganglion, and, dividing into 



