336 THE DOLABELLINAE. 



7a, 7b, and 7c, of the seventh pedal nerve, 7 ped., form anastomoses as follows: — 

 the branch 7a ramifies among the tubules of the organ of Bohadsch, o. B, also 

 sending a branch to unite with the nerve la from the first parietal nerve, p. 1 ; 

 7b sends numerous branches into the organ of Bohadsch, o. B, and finally unites 

 with the recurrent branch 2c of the second visceral nerve; while 7c, the more 

 anterior terminal branch of the seventh pedal, sends twigs to the dorsal peri- 

 toneum, and anastomoses with a delicate median branch of the second parietal 

 nerve, which is distributed to the same region. These relations are substantially 

 the same as those brought out by the writer (1909, p. 53) for Tethijs daclylomela 

 and Tethys cervina, in which forms the organ of Bohadsch is shown to be inner- 

 vated from both the right pedal and the left visceral ganglia. Plate 3, fig. -1 

 illustrates this arrangement for T. cervina. Here the third pedal nerve 3 ped, 

 sends the branches 3a and 3b to the organ of Bohadsch, o B, which is also inner- 

 vated by the recurrent anastomosing branch 2c, from the second visceral nerve, 

 v2, of the left side. In MazzarelU's (1890), study of the organ of Bohadsch in 

 the Mediterranean Aplysiidae he describes . the innervation as from the right 

 pedal ganglion alone, and disputes the earUer statement of Vayssidre (1885) as 

 to its innervation from the left visceral gangUon. The present writer's previous 

 position that both authors were in part correct is much strengthened by this 

 similar condition of double innervation, found in the more distantly related 

 DolabelUnae. 



The eighth pedal nerve, 8, arises just behind the sixth one, from the pos- 

 terior outer margin of the pedal ganglion. It is of moderate size, and passes 

 backward and dorsally along the body-wall, sending occasional branches to the 

 retractor muscles of the head. The main nerve bifurcates as it enters the 

 dorso-lateral body-wall, about midway of the length of the animal, its further 

 subdivisions passing mainly to the parapodia. Two small anastomosing 

 branches are also given off to the posterior subdivision of the seventh pedal 

 nerve, before the latter reaches its distribution in the organ of Bohadsch. 



The ninth, or posterior pedal nerve, 9, is the largest nerve from the pedal 

 ganglia. It arises from the posterior border of the gangUon and passes backward 

 below the head retractor muscles to the posterior region of the foot, where 

 it ramifies among its muscles and those of the adjacent body- wall. Close 

 to the origin of the ninth nerve on the left side, but some distance from that 

 point on the right one, a slender branch, 9a, is given off. On each side the 

 fibres of this deUcate nerve may be followed back in the common trunk to the 

 pedal gangUon. Upon the right side this branch forms an anastomosis with a 



