148 



oval dotted area). There was in the specimen sectioned 

 a discrete patch of cells on the right side on the R. 

 ventralis also, but in other examples these were con- 

 tinuous with and part of the extracranial ganglion. 



We follow Fiirbringer and Herrick in designating 

 the cephalic constituent of the first spinal by the letter h, 

 and the caudal constituent by the letter c. It will be 

 observed that the Plaice has three ventral roots instead of 

 the two described by Herrick in Menidia* and of these 

 the extra one is undoubtedly the first {v. h.^). 



The first spinal nerve of the Plaice has two dorsal 

 sensory (mostly) and three ventral motor roots. Of the 

 two dorsal roots the first {d. h.) is larger than the second 

 (d. c), and arises obviously from the spinal vth tract. 

 They both pass into the intracranial ganglion. Of the 

 three ventral roots, the first {v. b.^) is very long and 

 slender, and fuses with the second (y. h.). The third {v. c.) 

 is very short, and is the largest of all the roots. All three 

 ventral roots pass into the intracranial ganglion. 



The following nerves arise from the intracranial 

 ganglion : — - 



1. R. spinosus, b [r. sp. b.). — A motor nerve, arising 

 from the fused first and second ventral roots. It passes 

 through the intracranial ganglion, and leaves the exocci- 

 pital by a small foramen immediately above the main 

 foramen (indicated by a ring in the chart). It then passes 

 forwards over the top of the extracranial ganglion, rises 

 sharply at the side of the auditory capsule, and afterwards 

 turns forwards over the roof of the capsule to supply the 

 dorsal musculature and interspinal muscles. This nerve 

 does not anastomose with a sensory H. communicans like 

 the posterior E-H. spinosi. 



* Stannius mentions only four roots in the Plaice also, having 

 apparently missed the first ventral. 



