2o6 NERVE COMPONENTS OF BONY FISHES. 



more heavily myelinated. It gives off a fevi^ fibres from 

 time to time which join the rich sub-cutaneous plexus in 

 which they could not be further traced. 



When the dorsal musculature begins to appear the r. 

 lateralis accessorius follows the dorsal surface of this 

 muscle close under the skin and at about this level (600) 

 it receives the second anastomosing branch from the r. 

 supra-temporalis vagi. A short distance farther caudad it 

 receives two anastomosing branches from the dorsal r. 

 communicans b of the first spinal nerve, which break 

 through the dorsal musculature in the septum between the 

 general dorsal musculature and the interspinal muscles, 

 nearer the median line. The r. lateralis accessorius now 

 sinks down a short distance into the same intermuscular 

 septum, in which it continues into the trunk. It receives 

 a third anastomosing branch from the first spinal and 

 from this point caudad one such branch for each segment. 

 The first of these is formed by the union of one nerve 

 from the first spinal nerve and one from the second, the 

 second by one from the second spinal and one from the 

 third, and so on. See the account of the spinal nerves, 

 Section 4. Just caudad of the level of the third spinal 

 ganglion the r. lateralis accessorius is joined by the third 

 anastomosing branch from the r. lateralis vagi. 



The discussion of the morphology of the r. lateralis 

 accessorius is deferred until Section 12, which see. 



XI. — The Ramus Ophthalmicus Profundus. 



This nerve is said by most other authors to be absent 

 in the bony fishes, except in the siluroids. I find, how- 

 ever, that a portion of the Gasserian ganglion has been 

 isolated from the rest and fused more or less closely with 

 the most cephalic ganglion of the sympathetic chain and 



