THE VAGUS GROUP. 85 



Motor: supplies some of the motor fibres of the 

 first post-zonal ventral ramus [sensit stricto), a 

 few fibres probably for the depressor of the 

 pectoral fin and a small number for the levator 

 of the pectoral fin. 



Third spinal nerve, r. ventralis, 



Sensory: supplies all of the sensory fibres of the 

 first post-zonal ventral ramus, and sensory 

 fibres for the middle and ventral portions of 

 the pectoral fin. 



Motor: supplies most of the motor fibres of the 

 first post-zonal ventral ramus. 



The first spinal nerve is a fusion of at least two com- 

 plete segmental nerves whose motor components can be 

 clearly distinguished from each other. All four of these 

 roots emerge through the cranium, instead of behind it, 

 as in other teleosts. The reduction in the teleosts of the 

 first occipito-spinal nerve a is correlated with the absence 

 in the teleosts of the pre-hyal ventral spinal musculature. 

 Both this nerve and the corresponding musculature are 

 found in vertebrates both above and below the teleosts in 

 the taxonomic series. 



Section 5. — The Nerves of the Vagus Group. 



This section includes the account of the IX, X and XI 

 nerves, including the r. lateralis vagi. The glossophar- 

 yngeus and the r. lateralis are anatomically quite distinct 

 from the vagus; nevertheless they can best be described 

 together. These nerves in Menidia conform in general 

 to the usual teleostean arrangement, giving evidence in 

 some features of specialization parallel with an elaborate 

 branchial apparatus as a whole. 



