﻿228 
  On 
  the 
  Auditory 
  Apparatus 
  in 
  Sphenodon 
  punctatus. 
  

  

  believed 
  — 
  the 
  first 
  time, 
  and 
  a 
  full 
  account 
  of 
  the 
  developmental 
  changes 
  

   undergone 
  by 
  the 
  cartilaginous 
  structures 
  of 
  the 
  auditory 
  region 
  has 
  been 
  

   given. 
  That 
  the 
  cartilaginous 
  auditory 
  capsule 
  and 
  the 
  anterior 
  cornu 
  of 
  

   the 
  hyoid 
  are 
  products 
  of 
  two 
  connective-tissue 
  proliferations, 
  and 
  that 
  two 
  

   centres 
  of 
  chondrification 
  — 
  one 
  hyoidean 
  and 
  one 
  capsular 
  — 
  originally 
  

   separated 
  by 
  an 
  intervening 
  tract 
  of 
  mesenchyme, 
  are 
  found 
  is 
  indisputable, 
  

   and, 
  as 
  a 
  result 
  of 
  an 
  examination 
  of 
  the 
  developmental 
  changes 
  undergone 
  

   by 
  these 
  structures, 
  further 
  information 
  respecting 
  the 
  much-debated 
  question 
  

   as 
  to 
  the 
  origin 
  and 
  relationships 
  of 
  the 
  columellar 
  apparatus 
  has 
  been 
  

   obtained. 
  

  

  It 
  is 
  concluded 
  that 
  the 
  columella 
  auris 
  is 
  derived 
  from 
  the 
  hyoid 
  arch, 
  

   with 
  which 
  it 
  is 
  continuous 
  throughout 
  all 
  stages 
  of 
  development, 
  and 
  that 
  

   the 
  extra 
  stapedial 
  cartilage 
  is 
  primarily 
  united 
  with 
  the 
  anterior 
  cornu 
  of 
  

   the 
  hyoid. 
  The 
  supra- 
  stapedial 
  cartilage 
  (including 
  the 
  recurrent 
  process) 
  is 
  

   developed, 
  and 
  persists 
  as 
  an 
  outgrowth 
  from 
  the 
  extra-stapedial 
  cartilage, 
  

   and 
  is 
  therefore 
  a 
  hyoidean 
  derivative. 
  

  

  The 
  auditory 
  capsule 
  contributes, 
  at 
  most, 
  a 
  portion 
  of 
  the 
  foot-plate 
  of 
  the 
  

   stapes, 
  which 
  is 
  probably 
  partly 
  capsular 
  and 
  partly 
  hyoidean 
  in 
  origin. 
  

   The 
  distal 
  portion 
  of 
  the 
  stapes 
  is 
  exclusively 
  hyoidean. 
  At 
  no 
  period 
  

   of 
  its 
  life 
  history 
  does 
  Sphenodon 
  possess 
  any 
  cartilaginous 
  attachment 
  

   between 
  the 
  supra- 
  stapedial 
  cartilage 
  and 
  the 
  cranium, 
  but, 
  during 
  the 
  later 
  

   stages 
  of 
  the 
  embryonic 
  period, 
  and 
  in 
  adult 
  life, 
  there 
  is 
  a 
  secondary 
  

   attachment 
  between, 
  and 
  partial 
  fusion 
  of, 
  the 
  supra-stapedial 
  process 
  and 
  

   the 
  quadrate. 
  

  

  The 
  development 
  of 
  the 
  tympanic 
  cavity, 
  functional 
  tympanic 
  membrane,, 
  

   extra-columellar 
  sinew, 
  and 
  chorda 
  tympani 
  is 
  described. 
  It 
  is 
  noteworthy 
  

   that, 
  as 
  in 
  the 
  thick 
  embryo, 
  the 
  dorsal 
  portion 
  of 
  the 
  anterior 
  tympanic 
  

   diverticulum 
  undergoes 
  isolation, 
  and 
  finally 
  disappears. 
  

  

  The 
  results 
  now 
  obtained 
  support 
  the 
  contention 
  advanced 
  by 
  Gray 
  (1913) 
  

   that, 
  while 
  the 
  inner 
  ear 
  of 
  Sphenodon 
  differs 
  but 
  little 
  from 
  that 
  of 
  other 
  

   Keptilia 
  — 
  with 
  the 
  exception 
  of 
  Crocodilia 
  — 
  the 
  middle 
  ear 
  really 
  represents 
  

   a 
  transition 
  stage 
  in 
  the 
  evolution 
  of 
  the 
  middle 
  ear 
  of 
  the 
  living 
  Eeptilia. 
  

  

  