342 THE DOLABELLINAE. 



midway of the body-length at the posterior end of the anterior division of the 

 body-cavity, being placed nearly transversely above the aorta, and immediately 

 behind the anterior border of the liver, in front of and above the oblique body- 

 septum, or diaphragm. Externally it is located by the anterior ends of the 

 parapodia, being situated just below them and shghtly to the right of the median 

 line. The complex is of an elongated elliptical form, its double nature being 

 indicated by the entrance of the connectives from the pleural gangUa, but no 

 other external sign of its composition is evident. The left visceral ganglion 

 is placed in front of the right parietal one, the larger and more conspicuous 

 nerves emerging from the left end and doubling immediately around the aorta 

 and to the rear. The two moieties are connected with the corresponding pleural 

 gangha of the central nervous system by long connectives, the right parietal 

 ganglion to the right pleural one by the pleuro-visceral connective, Plate 2, 

 fig. 1, pl.-par. con, the left visceral division to the left pleural gangUon by the 

 pleuro-visceral connective, Plate 2, fig. 1, pl.-v. con. In addition to the figure 

 just cited the complex appears in Plate 3, fig. 2, Plate 4, fig. 1, and Plate 5, 



fig. 4. 



Visceral nerves. — From the left visceral ganglion two nerves arise. The 

 first of these (Plate 3, fig. 2, v 1) is given off from the inner posterior end of the 

 complex. It soon bifurcates into a more slender ramus which passes forward 

 to the peritoneum of the dorsal body-wall, and a stronger one which is dis- 

 tributed to the vesicle of Swammerdam or spermatotheca, and its duct. The 

 second visceral nerve arises as a very strong trunk from the posterior end of the 

 ganglion (Plate 3, fig. 2, v2, Plate 5, fig. 4). It at once divides into two equal 

 rami, doubling around below the aorta and to the right, and diverging as they 

 pass obliquely backward. The right one of these (Plate 5, fig. 4, v. 2a) crosses 

 obliquely backward below the loops of the large hermaphroditic duct. Its 

 distribution is best shown on Plate 3, fig. 2. It divides into two nearly equal 

 trunks, one of wliich, 2h, at once bifurcates into nearly equal branches, which 

 pass backward and are distributed, the one to the rectum and the adjacent 

 peritoneum, the other to the siphon and the peritoneum immediately surround- 

 ing it. The second trunk, 2c, sends a branch, 2d, to the peritoneum, and several 

 minor ones to ramify among the tubules of the organ of Bohadsch, the extent 

 of which is indicated by the dotted line, o. B. The remainder of the nerve 

 curves forward and anastomoses with a branch of the seventh pedal nerve 7h. 



The left one of the two rami (Plate 3, fig. 2, v 2b, Plate 5, fig. 4, v 2b) of 

 the second visceral nerve diverges backward from its fellow and sends off a 



