186 Thirty-fifth Beport ox the State Museum. 



ductor muscle, bifurcating when about half way through the muscle, 

 and giving forth numerous filaments : from the lower part of the pos- 

 terior portion a commissural cord proceeds, continuing to the upper 

 portion of the animal, just below the generative orifice, thence through 

 the glandular portion of the renal organ. Through the renal organ 

 the cords from the cerebral ganglia, that is, one from each ganglion, 

 are parallel and nearly contiguous to each other (PI. 12, o. b. n.) until 

 they approach the tendons of the posterior retractor muscles, when 

 they separate, passing over the exterior of the tendons, then rapidly ap- 

 proaching each other, and uniting with the posterior ganglion (PI. 

 9, 12, 13, p. s. g.). 



From the upper angle of the posterior portion of the cerebral gang- 

 lion a commissural cord passes dorsally and posteriorly, for a short 

 distance, nearly parallel with the commissural cord uniting the an- 

 terior and posterior ganglia (PI. 12, p. e. c; PI. 13, fig. 2, p. e. a); then 

 turning toward the posterior and ventral portion, it passes through the 

 substance of the liver, below the stomach, and unites with the pedal 

 ganglia^(Pl. 9, 12, p. g.). Sometimes branching from the nerve of the 

 anterior*adductor muscle, at other times proceeding directly from the 

 ganglion just posterior to the insertion of that nerve, there is a somewhat 

 finer one, which continues forward into the anterior portion of the 

 mantle (PI. 9, 12, a. m. n.). A peripheral nerve proceeds from the 

 under side of the ganglion, about midway between the ends, and passes 

 almost directly downward into the mantle (PI. 9, 12, a. m. n.) bifurcating 

 at a short distance from the ganglion — one branch continuing nearly 

 directly downward, the other continuing toward the posterior portion, 

 giving off several branches to the thickened muscular border of the 

 mantle, continuing apparent to the unaided eye, for a distance of a lit- 

 tle less than one-half the length of the mantle. 



The pedal ganglia (PI. 9, 12, p. g.) are situated in the body, about one- 

 fourth of its length from the anterior margin, thus being a little 

 posterior to the cerebral ganglia, and about one centimetre distant from 

 them, situated midway between the sides of the body; they consist of 

 two elongate oval bodies, which are joined to each other for about 

 one-half their length, which is a little less than three millimetres; 

 width, one millimetre. Their natural position is at an angle of forty- 

 five degrees to a vertical line through the body. From the upper end 

 proceeds the commissural cord connecting the cerebral and pedal 

 ganglia (PI. 9. 12, p. e. a). From the lower end proceeds a peripheral 

 nerve (PI. 9, 12, p. h. n.), which continues on a line with the ganglion, 

 having frequent branches, to one of which is attached the auditory 

 organ (PI. 9, 12. au. s.). From just beneath this nerve another nerve 

 proceeds, having the same general direction, but smaller. A little an- 



