Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 291 



sent downward along the internal surfaces of the next posterior 

 one or more segments. Certain of these latter branches anasto- 

 mosed with each other, a net-work of branches thus being formed 

 along the inner surface of the body wall. Whether or not any of 

 the terminal branches of the nerves innervated any part of the 

 trunk muscles could not be established. Near the proximal end of 

 each nerve a branch was always sent into the muscle of its seg- 

 ment, innervating it. 



The horizontal branch of each nerve ran at first downward to 

 the dorsal surface of the horizontal muscle septum, and then ran 

 outward along that septum, close to the anterior septum of its 

 segment, according to my notes, but, according to Dr. Dewitz's 

 sketches, rather nearer the posterior than the anterior septum. 



The dorsal branch of each nerve ran upward and backward, 

 gradually approaching the posterior septum of its segment, and 

 then continued its course close to that septum until it reached 

 the place where the septum turned sharply backward from its 

 associated dorsal vertebral arch toward the next posterior arch. 

 At this point the anterior septum of the segment passes close to 

 and, in its deeper portions, partly fuses with the posterior septum, 

 as already described. The nerve here gives off a branch which 

 continues in its own segment, the larger part of the nerve, how- 

 ever, continuing its upward and backward course and piercing 

 the anterior septum of its segment. The nerve then turns grad- 

 ually upward, or even upward and forward, and courses toward 

 the dorsal fin, traversing the first anterior segment, then the angle 

 of the dorso-posterior pocket of the next, or second anterior 

 muscle segment, then the first anterior segment again, then its 

 own segment, and then certain of the posterior segments. 



The anterior, or communicating branch of the nerve runs 

 almost directly upward, traverses the anterior septum of its seg- 

 ment and joins and anastomoses with the dorsal branch of the 

 next anterior nerve. 



The first and second spinal nerves differ from the fourth 

 to the sixth only in their ventral branches. Each of these ventral 

 branches, after traversing the horizontal muscle septum, sends 

 a branch into the muscle mass of the segment to which it belongs, 

 these branches corresponding exactly with the branches sent from 



