334 THE DOLABELLINAE. 



Pedal nerves. — Nine pairs of nerves arise from the lateral and posterior 

 margins of the pedal ganglia. They will be described in the order of their 

 occurrence from before backward as numbered in Plate 2, fig. 1, and in Plate 5, 

 fig. 2, the origin and distribution being the same for both right and left sides, 

 unless otherwise indicated. 



The first pedal nerve, 1, arises as a strong trunk from the outer anterior 

 portion of the superior face of the pedal gangUa. It passes directly forward 

 parallel to the bulbar aorta and gives off a slender external branch, la close 

 to its origin. This ramus is distributed mainly to the anterior region of the 

 lateral retractor muscles of the head, a large branch also forming an anastomosis 

 with the second pedal nerve, 3, as shown in the figure. At about 9.0 mm. from 

 its origin the main trunk of the first nerve bifurcates, its two subdivisions each 

 dividing in turn almost at once. The four main branches thus formed are 

 distributed to the most anterior portions of the foot. 



The second pedal nerve, 2, is strong, upon the left side being nearly as 

 large as the first. It arises from the antero-lateral face of the pedal gangUon, 

 just behind and external to the first nerve, and passes obliquely forward, receiv- 

 ing the anastomosing branch of the first, just above the lateral retractor of the 

 head. Passing between the fasciculi of this muscle to its outer face, it courses 

 forward between it and the body-wall, giving off branches to the lateral rectractor 

 and to the ventro-lateral body-wall at the margin of the foot. 



The third nerve, 3, is made up from the union of a number of delicate roots. 

 Upon the left side three of these may be distinguished, the first arising close above 

 the origin of the second nerve, the second from the lateral face of the pedal 

 gangUon, while the third is not a pedal nerve but arises from the left pleural 

 ganghon (pi. 1). These unite in a common epineural sheath and are distributed 

 to the lateral body-wall in front of the eye. On the right side at least three 

 delicate roots arise from the pedal gangUon, while a fourth springs from the 

 right pleural ganglion and joins the first three in a common sheath. The first 

 root appears to maintain its separate existence, the remaining three, or possibly 

 four uniting in a common trunk a short distance from the gangUon. The group 

 sends an anastomosing branch to the first cerebral nerve, and is distributed 

 to the lateral body-wall in front of the eye, and to the posterior retractor muscles 

 of the penis-sheath. 



The fourth pedal nerve, 4, arises from the ventro-lateral surface of the 

 pedal ganglion as a moderately strong trunk. It passes outward and forward 

 below the lateral retractor muscle to the ventro-lateral body-wall, and curves 



