54 OPISTHOBRANCHIATA OF BRAZIL 



and Tethys depilans as typical of his results. In figs. 38 and 39 of 

 the same plate I have made similar diagrams showing the innerva- 

 tion for Tethys dactylomela and Tethys cervina, according to my 

 dissections. Vayssiere ('85) describes and figures for Tethys 

 depilans a branch of the "nerf genital," which originates from the 

 left visceral ganglion (not from the right, as quoted by Mazza- 

 relli, p. 8), and passes to the "glande opaline," or gland of 

 Bohadsch, as in the forms here described. He does not find, how- 

 ever, the innervation from the pedal ganglion also. Mazzarelli 

 disputes the accuracy of the observations of Vayssiere, holding 

 that the nerve supply is from the pedal ganglion alone. In Tethys 

 dactylomela and Tethys cervina we have seen that both ganglia 

 in question send nerves to the Organ of Bohadsch, so in these 

 forms both authors would be partly right, and it would not be a 

 matter of great surprise to find, upon a reexamination of the 

 Mediterranean Aplysiidae that in them also the double innerva- 

 tion actually exists. 



3. The third nerve (PI. VIII, fig. 35 ; PI. X, fig. 42, /. v. j), 

 arises from the posterior margin of the left visceral ganglion and 

 courses backward, giving off a slender branch to the liver, crosses 

 the large hermaphroditic duct near its origin, sending a delicate 

 branch to it, swells into the small genital ganglion, (PI. VIII, fig. 

 35, g. g.), lying at the base of the adnexed genital mass, and 

 thence passes backward parallel to the small hermaphroditic duct 

 for nearly one-half the length of the latter. To this duct it sends 

 a branch (PI. VIII, fig. 35, v. ja), which passes backward along 

 its surface to the ovotestis, sending a few delicate branches to the 

 duct on the way. The main trunk (PI. VIII, fig. 35, v. J&), turns 

 abruptly to the right, leaving the hermaphroditic duct and, passing 

 backward, ramifies in the dorsal body wall in front of the anal 

 portion of the alimentary canal. 



4. The fourth nerve (PI. VIII, fig. 35 ; PL X, fig. 42, l.v.j), 

 equal in size to the second and third, arises at the posterior end 

 of the ganglion, close to the base of the third nerve, diverges to 

 the left, sending a branch to the liver, and courses obliquely across 

 below the pericardium to its posterior wall. A strong branch 

 (PI. VIII, fig. 35, 4a), is sent off about midway of this course 

 which ramifies to the ventricle and the pericardial wall, the main 

 trunk, (PI. VIII, fig. 35, 4b), curving dorsally in the posterior 



