340 THE DOLABELLINAE. 



3.0 mm. broad, while the apparent external dimensions reach a length of 3.0 

 mm. and a breadth of fully 5.5 mm. The gangUa are closely united by a very 

 short and broad buccal commissure. 



Buccal nerves. — From the buccal ganglia are given off three paired nerves 

 and a single unpaired median one. 



The anterior unpaired nerve (Plate 3, fig. 3, bl.) is completely concealed 

 from view by the capsule. Though apparently a single unpaired nerve, it 

 actually arises by a root from each ganglion, close in front of the commissure 

 upon the dorsal surface. These separate roots at once fuse into a single median 

 trunk which almost immediately bifurcates into two equal rami, that pass upward 

 into the ventral wall of the bulb. Each gives off several deUcate branches to 

 the superficial wall-muscles, and then penetrates upward and outward to the 

 rotella, to which each is distributed in a number of branches. Upon the dorsal 

 surface of the first nerve, immediately before its bifurcation, a pair of very 

 delicate branches, b la, are given off, which are distributed to the superficial 

 muscles of the floor of the bulb immediately in front of the buccal ganglion. 

 These are also shown in dorsal view in Plate 3, fig. 4, la. 



The paired nerves from the buccal gangha in Dolabella agassizi appear 

 upon their exit from the capsule as six independent nerves, corresponding to 

 the number given by Amaudrut (1886). This is at some distance from the 

 actual gangUa however, and in a cleared preparation the real origin of these 

 nerves may be traced back to the ganglia proper, and the apparent number 

 becomes reduced to but three main nerve-trunks upon each side. These 

 nerves are numbered in sequence in Plate 3, fig. 3 as b 2, b 3, and b 4, b 1 being 

 the single median trunk just described. 



The second buccal nerve, b 2, arises from the outer lateral margin of either 

 ganglion. It bifurcates at a short distance, giving rise to a posterior ramus, 

 c-h, con, which courses around the bulb dorsally and unites with the cerebral 

 ganglia, forming the cerebro-buccal connective (Plate 2, c-b. con.). The anterior 

 ramus of the second buccal nerve divides at once into two branches, 2c and 2d. 

 The branch 2d enters the large protractor bulbi muscle at its insertion into 

 the pharyngeal bulb and gives off a number of fine branches to it, the main 

 nerve passing on forward into the ventro-lateral muscles of the anterior portion 

 of the bulb itself, a slender branch being continued forward and distributed 

 to the anterior ventral protractor muscles of the bulb at their insertion into 

 the latter. The branch 2c passes obUquely forward and upward to the lateral 

 wall, above the insertion of the lateral protractor bulbi muscle, giving off several 



