﻿On 
  the 
  Auditory 
  Apparatus 
  in 
  Sphenodon 
  punctatus. 
  225 
  

  

  the 
  progressive 
  fusion 
  subsequently 
  undergone 
  by 
  these 
  primitive 
  arteries 
  

   supports 
  the 
  suggestion 
  advanced 
  by 
  Dendy 
  (1909) 
  that 
  the 
  (incompletely- 
  

   fused) 
  condition 
  of 
  the 
  arteria 
  basilaris 
  observed 
  by 
  him 
  in 
  adult 
  Sphenodon 
  

   is 
  reminiscent 
  of 
  an 
  earlier 
  paired 
  condition, 
  and 
  is 
  therefore 
  a 
  primitive 
  

   feature. 
  The 
  development 
  of 
  the 
  persistent 
  ductus 
  arteriosus 
  and 
  ductus 
  

   caroticus, 
  the 
  relationship 
  of 
  the 
  arteria? 
  laryngealis, 
  pulmonalis 
  and 
  cervici 
  

   muscularis, 
  and 
  the 
  progressive 
  reduction 
  and 
  ultimate 
  fate 
  of 
  the 
  aortic 
  

   arches 
  have 
  all 
  been 
  investigated. 
  It 
  has 
  also 
  been 
  shown 
  that 
  Sphenodon 
  is 
  

   similar 
  to 
  other 
  reptiles 
  in 
  respect 
  of 
  the 
  persistence 
  and 
  primitive 
  nature 
  of 
  

   the 
  arteria 
  stapedialis, 
  which 
  is 
  derived 
  from 
  a 
  persistent 
  dorsal 
  vestige 
  of 
  

   the 
  second 
  aortic 
  arch. 
  The 
  presence 
  of 
  a 
  number 
  of 
  newly-identified 
  

   branches 
  of 
  this 
  artery 
  (the 
  arteria? 
  tympanica, 
  dentalis 
  inferior, 
  temporalis 
  

   posterior 
  and 
  auricularis 
  posterior) 
  has 
  also 
  been 
  recorded. 
  As 
  regards 
  the 
  

   venous 
  trunks 
  of 
  the 
  auditory 
  region 
  the 
  most 
  conspicuously 
  primitive 
  features 
  

   are 
  the 
  persistence 
  of 
  the 
  tena? 
  cephalica?, 
  media? 
  and 
  posteriores 
  and 
  their 
  

   relationship 
  to 
  the 
  vena 
  capites 
  lateralis 
  and 
  to 
  the 
  primitive 
  head-veins 
  of 
  

   the 
  early 
  embryo. 
  The 
  presence 
  and 
  development 
  of 
  paired 
  venae 
  faciales, 
  

   tympanica?, 
  and 
  cochleares 
  have 
  now 
  been 
  recorded 
  for 
  the 
  first 
  time. 
  

  

  It 
  is 
  concluded 
  that 
  the 
  arrangement 
  of 
  the 
  blood 
  vessels 
  in 
  the 
  auditory 
  

   region 
  of 
  Sphenodon 
  is 
  similar 
  to, 
  but 
  more 
  primitive 
  than, 
  that 
  fomnd 
  in 
  

   Lacertilia. 
  

  

  The 
  region 
  investigated 
  includes 
  cranial 
  nerves 
  vi 
  — 
  xii, 
  the 
  development 
  of 
  

   which 
  was 
  worked 
  out 
  in 
  detail. 
  The 
  primitive 
  facial 
  nerve 
  early 
  shows 
  

   differentiation 
  into 
  one 
  pre-trematic 
  and 
  one 
  post-trematic 
  branch. 
  The 
  

   former 
  gives 
  rise 
  to 
  the 
  ramus 
  palatinus, 
  while 
  from 
  the 
  latter 
  develop 
  the 
  

   ramus 
  communicans 
  interna, 
  the 
  chorda 
  tympani 
  and 
  the 
  ramus 
  hyomandi- 
  

   bularis. 
  From 
  the 
  last-named 
  trunk 
  spring 
  the 
  delicate 
  ramus 
  recurrens 
  

   and 
  also 
  the 
  ramus 
  communicans 
  externa 
  which 
  passes 
  ventral 
  to 
  the 
  stapes 
  

   and, 
  ultimately 
  uniting 
  with 
  the 
  ramus 
  communicans 
  interna, 
  enters 
  the 
  

   ganglion 
  petrosum. 
  

  

  The 
  development 
  of 
  nerves 
  vi, 
  ix, 
  x 
  and 
  xi 
  presents 
  no 
  abnormal 
  features. 
  

   Within 
  the 
  foramen 
  jugulare 
  the 
  roots 
  of 
  nerves 
  ix, 
  x 
  and 
  xi 
  enter 
  an 
  

   incompletely-trilobed 
  ganglion 
  of 
  which 
  the 
  three 
  component 
  bundles 
  of 
  

   tibres 
  are 
  clearly 
  differentiated 
  and 
  between 
  which 
  the 
  passage 
  of 
  few 
  

   communicating 
  fibres 
  can 
  be 
  observed. 
  The 
  roots 
  of 
  nerve 
  xii 
  undergo, 
  as 
  

   development 
  proceeds, 
  a 
  progressive 
  reduction 
  in 
  number 
  from 
  five 
  to 
  two, 
  

   the 
  foramina 
  by 
  which 
  they 
  emerge 
  from 
  the 
  exoccipital 
  region 
  of 
  the 
  

   parachordal 
  plate 
  being 
  similarly 
  reduced 
  in 
  number 
  from 
  four 
  to 
  two. 
  

  

  The 
  general 
  development 
  of 
  the 
  inner 
  ear 
  and 
  auditory 
  nerve 
  is 
  thoroughly 
  

   normal. 
  The 
  auditory 
  organ 
  appears 
  as 
  a 
  nearly 
  circular, 
  and 
  slightly 
  hollowed 
  

  

  T 
  2 
  

  

  