﻿166 
  Mr. 
  A. 
  Sanders 
  on 
  the 
  

  

  which 
  are 
  distributed 
  on 
  the 
  inferior 
  surface 
  of 
  the 
  otic 
  vesicle, 
  

   one 
  branch 
  going 
  to 
  the 
  external, 
  the 
  other 
  to 
  the 
  internal 
  

   division 
  of 
  that 
  vesicle. 
  

  

  Ninth 
  pair. 
  — 
  The 
  glossopharyngeal 
  has 
  not 
  a 
  distinct 
  and 
  

   independent 
  root 
  in 
  Ceratodus, 
  but 
  is 
  a 
  branch 
  of 
  the 
  vagus, 
  

   and 
  will 
  be 
  described 
  with 
  that 
  nerve. 
  

  

  Tenth 
  pair 
  (PI. 
  VIII. 
  fig. 
  I, 
  n. 
  10). 
  — 
  The 
  vagus 
  arises 
  by 
  

   five 
  contiguous 
  roots 
  on 
  the 
  right 
  side 
  and 
  by 
  four 
  on 
  the 
  

   left 
  ; 
  the 
  outer 
  and 
  anterior 
  root 
  is 
  the 
  largest 
  in 
  both 
  cases. 
  

  

  The 
  first 
  branch 
  is 
  given 
  off 
  at 
  right 
  angles 
  to 
  the 
  course 
  

   of 
  the 
  nerve 
  and 
  is 
  the 
  glossopharyngeal 
  ; 
  after 
  a 
  short 
  course 
  

   this 
  branch 
  enlarges 
  into 
  a 
  ganglion, 
  the 
  distal 
  end 
  of 
  which 
  

   is 
  the 
  broader 
  ; 
  from 
  this 
  ganglion 
  three 
  branches 
  are 
  given 
  

   off. 
  The 
  most 
  anterior, 
  which 
  is 
  the 
  largest, 
  plunges 
  down 
  

   in 
  front 
  of 
  the 
  branchial 
  chamber 
  and 
  supplies 
  the 
  membrane 
  

   lining 
  the 
  anterior 
  wall 
  of 
  that 
  chamber; 
  the 
  middle 
  branch 
  

   is 
  supplied 
  to 
  the 
  membrane 
  between 
  the 
  first 
  branchial 
  arch 
  

   and 
  the 
  anterior 
  wall 
  of 
  the 
  branchial 
  chamber; 
  the 
  third 
  

   branch 
  runs 
  along 
  the 
  first 
  branchial 
  arch 
  between 
  the 
  two 
  

   lamellee 
  of 
  the 
  branchiae 
  to 
  the 
  ventral 
  surface, 
  where 
  its 
  

   terniii 
  ating 
  branches 
  are 
  distiibuted 
  to 
  the 
  pharynx. 
  

  

  A 
  short 
  distance 
  behind 
  the 
  glossopharyngeal 
  a 
  large 
  gan- 
  

   glion 
  is 
  attached 
  to 
  the 
  inferior 
  surface 
  of 
  the 
  main 
  trunk 
  of 
  

   the 
  vagus 
  (PI. 
  VIII. 
  fig. 
  1, 
  gn. 
  v.) 
  ; 
  this 
  ganglion 
  ends 
  in 
  

   three 
  expansions, 
  having 
  first 
  given 
  off 
  a 
  small 
  communicating 
  

   nerve 
  to 
  the 
  glossopharyngeal 
  ; 
  the 
  three 
  terminating 
  gan- 
  

   glia 
  supply 
  branches 
  to 
  the 
  membrane 
  closing 
  the 
  spaces 
  

   between 
  the 
  branchial 
  arches, 
  and 
  each 
  gives 
  off 
  a 
  nerve 
  

   (PI. 
  VIII. 
  fig. 
  1, 
  b.) 
  which 
  runs 
  in 
  a 
  groove 
  at 
  the 
  base 
  of 
  the 
  

   branchiae 
  to 
  the 
  ventral 
  side, 
  where 
  it 
  terminates 
  in 
  the 
  same 
  

   way 
  as 
  the 
  branchial 
  branches 
  of 
  the 
  glossopharyngeal. 
  In 
  

   addition, 
  the 
  third 
  swelling 
  gives 
  off 
  a 
  large 
  nerve, 
  which 
  

   passes 
  on 
  behind 
  the 
  branchial 
  chamber 
  and 
  becomes 
  the 
  

   visceral 
  branch, 
  of 
  the 
  vagus. 
  

  

  The 
  main 
  continuation 
  of 
  the 
  nerve, 
  after 
  giving 
  off 
  the 
  

   above-mentioned 
  ganglion, 
  passes 
  backward 
  along 
  the 
  side 
  of 
  

   the 
  vertebral 
  column 
  as 
  the 
  ramus 
  lateralis 
  (PI. 
  V11I. 
  fiff. 
  1, 
  

   r. 
  I.) 
  . 
  

  

  The 
  origin 
  of 
  the 
  vagus, 
  as 
  thus 
  described, 
  differs 
  consider- 
  

   ably 
  from 
  that 
  of 
  the 
  corresponding 
  nerve 
  of 
  Protopterus*, 
  

   in 
  which 
  it 
  arises 
  by 
  both 
  dorsal 
  and 
  ventral 
  roots, 
  which 
  all 
  

   end 
  in 
  the 
  ganglion, 
  the 
  consequence 
  being 
  that 
  none 
  of 
  the 
  

   branches 
  are 
  independent 
  of 
  that 
  body. 
  

  

  Two 
  nerves 
  arise 
  from 
  the 
  ventral 
  side 
  of 
  the 
  posterior 
  end 
  

   ot 
  the 
  fourth 
  ventricle 
  behind 
  the 
  vagus 
  ; 
  they 
  originate 
  like 
  

   * 
  VViecloi'slieim, 
  /. 
  c. 
  

  

  