﻿[23] 
  DEVELOPMENT 
  OF 
  THE 
  CETACEA. 
  449 
  

  

  the 
  longest 
  digit 
  for 
  a 
  time, 
  would 
  become 
  the 
  fifth 
  instead 
  of 
  the 
  first, 
  

   when 
  counted 
  from 
  within 
  outwards. 
  The 
  hallux 
  then 
  probably 
  grew 
  

   gradually 
  shorter 
  when 
  the 
  second 
  and 
  third 
  digits 
  became 
  the 
  princi- 
  

   pal 
  ones 
  in 
  the 
  pes 
  as 
  well 
  as 
  in 
  the 
  manus, 
  after 
  which 
  they 
  atrophied 
  

   entirely, 
  leaving 
  only 
  the 
  vessels 
  to 
  serve 
  as 
  traces 
  of 
  their 
  former 
  pres- 
  

   ence. 
  

  

  The 
  extremely 
  short 
  neck 
  of 
  the 
  cetaceans, 
  due 
  to 
  the 
  abbreviation 
  

   of 
  the 
  cervical 
  vertebrae, 
  has 
  brought 
  the 
  origins 
  of 
  the 
  fore 
  limbs 
  nearer 
  

   the 
  head 
  and 
  to 
  some 
  extent 
  obscured 
  the 
  inclusion 
  by 
  the 
  soft 
  parts 
  

   of 
  the 
  arm 
  and 
  fore-arm 
  which 
  has 
  taken 
  place 
  in 
  these 
  forms. 
  Such 
  

   an 
  inclusion 
  of 
  the 
  proximal 
  joints 
  of 
  the 
  fore 
  limbs 
  has 
  also 
  occurred 
  

   in 
  the 
  pinnipeds, 
  but 
  in 
  them, 
  as 
  in 
  Eumetopias, 
  for 
  example, 
  the 
  nor- 
  

   mal 
  length 
  of 
  cervical 
  vertebras 
  has 
  been 
  retained, 
  so 
  that 
  when 
  the 
  

   living 
  animal 
  is 
  observed 
  the 
  neck 
  seems 
  longer 
  than 
  it 
  actually 
  is, 
  be- 
  

   cause 
  of 
  the 
  inclusion 
  of 
  the 
  upper 
  parrs 
  of 
  the 
  fore 
  limb 
  so 
  as 
  to 
  leave 
  

   little 
  more 
  than 
  the 
  manus 
  free, 
  a 
  condition 
  which 
  gives 
  rise 
  to 
  the 
  il- 
  

   lusive 
  appearance 
  of 
  a 
  long 
  neck 
  ; 
  in 
  fact, 
  the 
  neck 
  of 
  the 
  sea-lion 
  as 
  

   beheld 
  and 
  understood 
  by 
  one 
  knowing 
  nothing 
  of 
  the 
  internal 
  anat- 
  

   omy 
  of 
  the 
  animal, 
  would 
  include 
  some 
  of 
  the 
  anterior 
  dorsal 
  or 
  trunk 
  

   vertebrae, 
  together 
  with 
  the 
  true 
  cervicals. 
  In 
  the 
  whales, 
  however, 
  so 
  

   great 
  has 
  been 
  the 
  actual 
  shortening 
  of 
  the 
  neck 
  that 
  the 
  effect 
  of 
  the 
  

   inclusion 
  of 
  the 
  proximal 
  parts 
  of 
  the 
  fore 
  limb 
  on 
  the 
  apparent 
  length 
  

   of 
  the 
  neck 
  is 
  lost, 
  but 
  if 
  the 
  neck 
  vertebras 
  of 
  a 
  cetacean 
  are 
  imagined 
  

   to 
  be 
  of 
  their 
  usual 
  proportional 
  length 
  in 
  a 
  skeleton, 
  and 
  if 
  the 
  exten- 
  

   sion 
  so 
  gained 
  be 
  added 
  with 
  a 
  pair 
  of 
  dividers 
  to 
  a 
  figure 
  of 
  the 
  latter 
  

   the 
  effects 
  of 
  the 
  inclusion 
  of 
  the 
  upper 
  parts 
  of 
  the 
  fore 
  limb 
  at 
  once 
  

   become 
  apparent. 
  In 
  foetal 
  cetaceans 
  the 
  neck 
  is 
  proportionally 
  some- 
  

   what 
  longer 
  than 
  in 
  the 
  adults. 
  

  

  (14) 
  The 
  auditory 
  bulke 
  of 
  Phoeidce 
  and 
  rudimentary 
  pinnae 
  in 
  Cctacea. 
  — 
  

   It 
  is 
  worthy 
  of 
  notice 
  that 
  the 
  bulla 
  tympani 
  in 
  the 
  Phocidw 
  are 
  very 
  

   large 
  and 
  thick 
  walled 
  and 
  not 
  so 
  intimately 
  joined 
  to 
  the 
  adjacent 
  

   bones 
  of 
  the 
  skull 
  as 
  in 
  the 
  typical 
  land 
  Carnivora, 
  thus 
  approximating 
  

   the 
  Cetacea 
  somewhat. 
  The 
  eared 
  seals 
  have 
  a 
  distinct 
  though 
  rudi- 
  

   mentary 
  pinna 
  or 
  external 
  ear 
  developed, 
  which 
  is 
  wanting 
  in 
  the 
  PJio- 
  

   cidce. 
  That 
  even 
  the 
  ancestry 
  of 
  the 
  Cetacea 
  were 
  possessed 
  of 
  well 
  

   developed 
  pinnae 
  or 
  external 
  ears 
  seems 
  to 
  be 
  countenanced 
  by 
  the 
  fact 
  

   that 
  Howes* 
  has 
  found 
  a 
  minute 
  cylindrical 
  appendage 
  close 
  to 
  and 
  

   just 
  behind 
  the 
  external 
  auditory 
  meatus 
  of 
  the 
  embryo 
  of 
  Phocwna, 
  

   Such 
  rudiments 
  of 
  pinnas 
  seem 
  to 
  be 
  unusual 
  iu 
  embryo 
  Cetaceans, 
  as 
  

   the 
  writer 
  has 
  not 
  found 
  them 
  present 
  in 
  any 
  of 
  the 
  foetuses 
  of 
  the 
  

   species 
  examined 
  by 
  him. 
  

  

  II. 
  — 
  Development. 
  

  

  In 
  all 
  the 
  figures 
  of 
  cetacean 
  embryos 
  which 
  have 
  been 
  published 
  

   and 
  to 
  which 
  I 
  have 
  had 
  access, 
  the 
  same 
  law 
  which 
  presides 
  over 
  the 
  

  

  "Journ. 
  Anat. 
  and 
  Physiol., 
  XIV. 
  

   8. 
  Mis. 
  70 
  29 
  

  

  