TETHYS CERVINA BALL AND SIMPSON 49 



above it, another (fig. 35, jc), to the Organ of Bohadsch, or 

 hypobranchial gland, and finally (fig. 35, j/), unites with the 

 first nerve from the right parietal ganglion, thus forming a 

 parieto-pedal connective. From the above mentioned branch 

 (fig. 35, j&), to the lateral retractor of the head a branch is given 

 off which courses backward along the body wall, passes beneath 

 the right margin of the Organ of Bohadsch, and well beyond the 

 latter forms an anastomosis at an acute angle with the recurrent 

 branch (fig. 35, 2c) of the second nerve (fig. 35, /. v. 2), of the 

 left visceral ganglion, which also sends a branch to the Organ 

 of Bohadsch, as will be described below. In Tethys dactylomela 

 the third pedal nerve is represented by two separate nerves, the 

 second and third of the description on page 28, they correspond- 

 ing in their distribution to the third nerve alone of T. cervina. 



The fourth pedal nerve (4) is long and slender, arising from 

 the outer margin of the ganglion and passing backward to the 

 parapodium of the same side. 



The fifth pedal nerve (5) is a strong one from the median 

 lateral margin of the ganglion. Close to its origin it gives off a 

 slender branch {5a) which might possibly be considered a separate 

 nerve, though its distribution is the same as that of the main 

 nerve, to the parapodium. In T. dactylomela a similar branch 

 is given off from the fifth nerve, but its origin is further removed 

 from the base of that nerve. Its distribution is the same as that 

 here indicated. 



The sixth, or posterior pedal nerve {6) is the longest of the 

 nerves from the pedal ganglion. It arises from the mid-lateral 

 margin of the ganglion, curves backward, unbranched for over 

 one-half of its course, and is distributed to the posterior portion 

 of the foot. 



The seventh pedal nerve (7) arises upon the lower portion 

 of the ventro-anterior face of the ganglion, below the origin of 

 the first and second nerves. Like these and the ninth is is closely 

 imbedded in the connective tissue surrounding the pharyngeal 

 bulb and may be dissected out with some difficulty. A branch of 

 the seventh forms an anastomosis with the ninth, and both are 

 distributed to the muscles and integument of the side of the head. 

 The nerves of both sides are alike in origin and distribution. 



The eighth, or median pedal nerve {8) is a strong trunk 



