﻿464 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  [38] 
  

  

  the 
  limb 
  in 
  the 
  cetaceans 
  has 
  atrophied, 
  that 
  is, 
  the 
  phalanges 
  first, 
  

   then 
  the 
  tarsus, 
  then 
  the 
  fibula 
  and 
  tibia, 
  and 
  finally 
  the 
  femur, 
  affect- 
  

   ing 
  also 
  more 
  or 
  less 
  the 
  degeneration 
  of* 
  the 
  pelvic 
  girdle. 
  

  

  Bnt 
  it 
  will 
  be 
  inquired, 
  why 
  do 
  the 
  limb-folds, 
  or 
  pedal 
  folds, 
  Avhich 
  

   represent 
  the 
  former 
  in 
  cetaceans, 
  grow 
  out 
  at 
  all 
  after 
  such 
  extensive 
  

   atrophy 
  of 
  the 
  limb 
  skeleton"? 
  To 
  this 
  it 
  may 
  be 
  replied 
  that 
  the 
  distal 
  

   parts 
  of 
  limb-folds 
  generally 
  do 
  not 
  at 
  first 
  have 
  the 
  skeleton 
  developed 
  

   within 
  them 
  at 
  all, 
  and 
  that, 
  as 
  I 
  have 
  pointed 
  out, 
  the 
  limb 
  bones 
  de- 
  

   velop 
  from 
  within 
  outwards; 
  the 
  terminal 
  part 
  of 
  the 
  limb-fold, 
  or 
  epi- 
  

   dermal 
  pocket 
  representing 
  it, 
  contains 
  at 
  first 
  nothing 
  but 
  undifferen- 
  

   tiated 
  mesoblast. 
  It 
  thus 
  seems 
  to 
  me 
  that 
  in 
  the 
  skeletonless 
  flukes 
  

   we 
  have 
  this 
  inverse 
  method 
  of 
  development 
  illustrated, 
  and 
  that 
  the 
  

   flukes 
  represent 
  the 
  earliest 
  condition 
  of 
  a 
  pes 
  and 
  therefore 
  the 
  last 
  to 
  

   vanish, 
  unless 
  indeed 
  the 
  flukes 
  represent 
  the 
  produced 
  integuments 
  

   distad 
  of 
  the 
  last 
  phalanges 
  of 
  pinnipeds, 
  which 
  I 
  think 
  hardly 
  prob- 
  

   able, 
  for 
  the 
  reason 
  that 
  their 
  blood-supply, 
  as 
  already 
  described, 
  sim- 
  

   ulates 
  that 
  of 
  the 
  normal 
  mammalian 
  pes. 
  

  

  Struthers' 
  figures 
  indicate 
  that 
  the 
  femora 
  are 
  adducted 
  distally 
  in 
  

   Balcena 
  mysticetus 
  to 
  a 
  remarkable 
  extent, 
  in 
  fact 
  to 
  such 
  a 
  degree 
  that 
  

   if 
  the 
  limb 
  were 
  fully 
  developed 
  with 
  the 
  cms 
  extended 
  in 
  a 
  line 
  with 
  

   the 
  shaft 
  of 
  the 
  femur, 
  the 
  limbs 
  of 
  opposite 
  sides 
  would 
  cross 
  each 
  

   other. 
  This 
  adduction 
  of 
  the 
  femora 
  by 
  which 
  their 
  distal 
  moieties 
  ap- 
  

   proximate 
  each 
  other, 
  is 
  probably 
  due 
  to 
  the 
  after 
  effects 
  of 
  the 
  process 
  

   of 
  inclusion 
  which 
  must 
  have 
  begun 
  with 
  a 
  seal-like 
  ancestral 
  form, 
  

   and 
  which 
  has 
  reached 
  its 
  extremest 
  expression 
  in 
  existing 
  cetaceans, 
  

   where 
  the 
  growth 
  of 
  the 
  subcaudal 
  muscles 
  has 
  influenced 
  their 
  final 
  

   position. 
  

  

  The 
  inclusion 
  and 
  degeneracy 
  of 
  the 
  pelvis 
  of 
  cetaceans 
  being 
  so 
  

   complete, 
  there 
  is 
  however 
  not 
  so 
  great 
  a 
  posterior 
  extension 
  of 
  the 
  ab- 
  

   dominal 
  muscles 
  backward 
  as 
  oue 
  might 
  be 
  led 
  to 
  expect, 
  but 
  certain 
  

   muscles 
  are 
  nevertheless 
  provided 
  with 
  remarkably 
  posterior 
  insertions. 
  

  

  V. 
  — 
  The 
  caudal 
  muscles 
  of 
  cetacea. 
  

  

  These 
  are 
  dorsally 
  continuations 
  of 
  the 
  deep 
  multifidus 
  spince 
  and 
  the 
  

   superficial 
  (rector 
  spina, 
  posteriorly; 
  anteriorly 
  as 
  continuations 
  of 
  the 
  

   above, 
  as 
  found 
  in 
  the 
  human 
  subject, 
  the 
  sacrolumbal 
  is, 
  longissimus 
  

   dorsi, 
  spinalis 
  dorsi, 
  and 
  possibly 
  the 
  semispinalis 
  of 
  man 
  are 
  represented 
  

   in 
  the 
  vast 
  dorsal 
  and 
  supracaudal 
  musculature 
  of 
  whales. 
  Murie* 
  

   states 
  that 
  in 
  the 
  black-fish 
  "the 
  longissimus 
  dorsi 
  and 
  spinalis 
  dorsi 
  

   are 
  most 
  intimately 
  bound 
  up 
  together 
  in 
  the 
  dorsal 
  region, 
  forming 
  a 
  

   long, 
  but 
  enormous 
  fleshy 
  mass, 
  interwoven 
  spinally 
  and 
  costal! 
  y 
  with 
  

   tendinous 
  fascia. 
  That 
  which 
  may 
  be 
  considered 
  equivalent 
  to 
  a 
  trans- 
  

   versalis 
  cervicis 
  commences 
  by 
  a 
  short, 
  strong 
  tendon 
  at 
  the 
  paramas- 
  

   toid. 
  Immediately 
  becoming 
  fleshy 
  and 
  thick, 
  it 
  ascends 
  posteriorly 
  

  

  * 
  On 
  tlio 
  organization 
  of 
  the 
  Caaing 
  Whale 
  (GloMocephalw 
  melas), 
  Trans. 
  Zool. 
  Soc. 
  

   London, 
  VIII, 
  1872-74, 
  pp. 
  230-301, 
  pis. 
  30-38. 
  

  

  