080 MnS. O. A.' MERRTTT HAWKES ox THE [Dec. 11, 



The small dorsal branches of the Vagus run very near to the 

 dorsal branch of the ninth and it is possible that one might be 

 mistaken for the other. Branch B passes dorsad and soon divides 

 into a number of smaller branches which supply approximately 

 the first 2 cm. of the open body-canal. 



The posterior two-thirds of the vagal ganglion can with difficulty 

 be partly dissected. On the inner side it consists mainly of a 

 large portion apparently indivisible, which gives rise to the lateral 

 line nerve and is therefore the representative of the lateral line 

 ganglion. On the outer side it consists of the basal portions of 

 four nerves, which in a side view hide the lateral line ganglion. 



The first third of the vagal ganglion is indivisible, and presumably 

 contains the ganglion-cells of the intestinal branch and of those 

 bi'anchial branches which, so far as can be seen by dissection, have 

 no separate ganglia. 



In one specimen, branches A and B arose directly from the vagal 

 ganglion instead of between the origin of the nerve and the 

 ganglion. Here branch B passed dorsad and then caudad for 

 about 4 cm., giving oflT a number of branches which supplied 

 between 20 and 25 neuromasts, which were situated at irregular 

 intervals, in places being only 2 mm. apart. The first 4 cm. of 

 the Vagus is spirally ai'ranged within the nerve-sheath. This 

 allows for the considerable stretching that occurs with movements 

 of the branchial "frills." 



From the latei'al line ganglion there pass two equal lateral line 

 nerves which unite into a single strand for a distance of 1 to 2 cm. 

 These strands anastomose irregulai'ly. The more dorsal nerve in 

 one case gave ofi" 8 fine branches to the neuromasts. In another 

 •specimen it gave off no branches. 



(a) The lateral line nerve, a wide riband-like strand, passes 

 caudad and somewhat ventrally, giving off dorsally numerous very 

 fine nerves to the neuromasts. After a course of about 5 or 6 cm., 

 the nerve disappeai'S between the longitudinal dorsal muscles and 

 passes alongside the vertebi-al column about 3 cm. from the surface 

 of the body. At intervals along the body, the main nerve is 

 separated into two strands which reiuiite at distances varying from 

 1 to 2 cm. Fine dorsal branches are given off at intervals equal 

 to about one and a half m3rotomes. The branches su^^ply from 

 about 5 to 9 neuromasts each. They may divide either immediately 

 after leaving the main nerve or not until near the final distribution. 

 They have a long course (4 to 6 cm.), difficult to dissect, each 

 describing approximately a, semicircle. In Chlamycloselachus, as in 

 the common Dogfish, the lateralis nerve is situated deeply, but in 

 the former more deeply than in the latter. This is curious and 

 difficult to explain, as the lateralis system in this species is primitive 

 I'elatively to that of a Dogfish. 



(h) Vagus 1. The first bi'anchial division of the Vagus can be 

 dissected out from the ganglionic mass to a point as far forwards 

 as the first third of the ganglion. At this point the nerve has a 

 flattened ganglionic swelling. Immediately above the second cleft 



