290 ALUS. [Vol. XVIII. 



and somewhat dorsal to it, and it is from it and not from the 

 main nerve that the branches to the sense organs of the lateral 

 line of the body arise, as far back as the dissections were carried. 

 At certain intervals branches from the main nerve join the acces- 

 sory one. That the lateral line nerve of Scomber is found in two 

 parallel portions is stated by Stannius. 



The first branch that arises from this accessory nerve enters 

 the suprascapular and innervates the second organ in that bone, 

 organ No. 16 infraorbital. The second branch innervates the 

 organ in the supraclavicular and also the organ in the first scale 

 of the lateral line. The third branch innervates the organ in the 

 second scale of the lateral line, and was the last one traced. 



II. Occipital and First Spinal Nerves. 



The ganglion of each of the first six spinal nerves lies 

 nearer the anterior than the posterior septum of the muscle seg- 

 ment to which it belongs, the relative distance from that septum 

 increasing regularly from the first to the sixth nerve. From 

 each ganglion four nerves arise, as in Ainia, a ventral nerve or 

 branch, a horizontal one, a dorsal one, and an anterior or com- 

 municating one. 



The ventral branch of each of the posterior four nerves ex- 

 amined first runs downward and backward along the lateral sur- 

 face of its vertebra, toward the posterior septum of its segment, 

 and then passes downward through an open space found in the 

 horizontal septum, immediately in front of that horizontal rib that 

 lies in the transverse septum posterior to the segment. It then 

 reaches the inner surface of the trunk muscles, that is the lining 

 wall of the body cavity, and turning relatively forward gradually 

 approaches the anterior transverse septum of its segment and its 

 associated ventral rib, which it reaches slightly proximal to the 

 ventro-posterior angle of the septum. Here the third, fourth and 

 sixth nerves, in the specimen examined, turned forward and down- 

 ward mesial to the anterior ventral ribs of their respective seg- 

 ments, the fifth nerve taking the same course but passing lateral 

 to the anterior rib of its segment. The anterior parts of all the 

 nerves then followed, approximately, the course of the anterior 

 parts of their muscle segments, branches however being always 



