﻿45'0 
  REPORT 
  OF 
  COMMISSIONER 
  OP 
  FISH 
  AND 
  FISHERIES. 
  [24] 
  

  

  order 
  of 
  the 
  outgrowth 
  of 
  the 
  limbs 
  is 
  shown 
  to 
  hold 
  as 
  for 
  all 
  other 
  

   vertebrates, 
  provided 
  the 
  fluke 
  folds 
  be 
  regarded 
  as 
  representative 
  of 
  

   the 
  hinder 
  limb 
  folds; 
  otherwise 
  the 
  cetaceans 
  must 
  be 
  regarded 
  as 
  

   anomalous 
  or 
  exceptional 
  in 
  this 
  respect 
  and 
  permanently 
  without 
  any 
  

   traces 
  of 
  externally 
  developed 
  posterior 
  appendicular 
  organs, 
  even 
  in 
  

   the 
  embryonic 
  condition. 
  Granting, 
  however, 
  that 
  the 
  discussion 
  of 
  

   the 
  morphology 
  of 
  the 
  adult 
  has 
  justified 
  the 
  acceptance 
  of 
  the 
  doctrine 
  

   of 
  the 
  translocation 
  of 
  the 
  limb 
  backwards 
  by 
  the 
  progressive 
  inclusion 
  

   of 
  more 
  and 
  more 
  of 
  the 
  proximal 
  parts 
  of 
  the 
  hind 
  limbs 
  of 
  some 
  

   decidedly 
  ambulatory 
  ancestral 
  form 
  by 
  the 
  gradual 
  advance 
  from 
  be- 
  

   fore 
  of 
  the 
  integuments 
  of 
  the 
  body 
  in 
  common 
  over 
  the 
  hind 
  limbs 
  and 
  

   tail 
  until 
  nothing 
  but 
  the 
  feet 
  have 
  remained 
  exserted, 
  a 
  process 
  which 
  

   we 
  see 
  has 
  already 
  begun 
  and 
  reached 
  a 
  very 
  marked 
  development 
  in 
  

   the 
  existing 
  pinnipeds, 
  the 
  reader 
  maybe 
  led 
  to 
  admit 
  that 
  my 
  hypothe- 
  

   sis 
  when 
  applied 
  to 
  the 
  interpretation 
  of 
  the 
  order 
  of 
  appearance 
  of 
  

   certain 
  parts 
  in 
  the 
  embryo 
  is 
  not 
  so 
  unreasonable 
  as 
  might 
  at 
  first 
  be 
  

   supposed. 
  lie 
  must 
  at 
  any 
  rate 
  admit 
  that 
  the 
  process 
  which 
  has 
  be- 
  

   gun 
  to 
  modify 
  the 
  limbs 
  and 
  pelvic 
  girdle 
  of 
  pinnipeds 
  if 
  carried 
  still 
  

   farther 
  must 
  actually 
  lead 
  toward 
  what 
  now 
  exists 
  in 
  the 
  cetaceans; 
  

   and 
  that 
  as 
  a 
  result 
  of 
  the 
  process 
  of 
  inclusion 
  of 
  the 
  limbs 
  their 
  skele- 
  

   ton 
  must 
  necessarily 
  first 
  become 
  immobile 
  and 
  then 
  atrophy, 
  and 
  that 
  

   not 
  only 
  the 
  muscles 
  but 
  the 
  nerves 
  and 
  vessels 
  must 
  also 
  atrophy 
  or 
  be 
  

   so 
  modified 
  as 
  to 
  leave 
  scarcely 
  any 
  recognizable 
  representatives 
  of 
  

   their 
  homologues 
  as 
  found 
  in 
  the 
  hind 
  limbs 
  of 
  normal 
  mammals. 
  We 
  

   are 
  thus, 
  I 
  venture 
  to 
  fully 
  believe, 
  put 
  upon 
  the 
  clew 
  which 
  will 
  lead 
  

   us 
  along 
  the 
  course 
  which 
  the 
  evolution 
  of 
  the 
  cetacean 
  tail 
  has 
  taken 
  ; 
  

   and, 
  while 
  asserting 
  that 
  the 
  pinnipeds 
  very 
  distinctly 
  give 
  us 
  the 
  inti- 
  

   mation 
  of 
  how 
  this 
  structure 
  was 
  developed, 
  it 
  does 
  not 
  necessarily 
  fol- 
  

   low 
  that 
  the 
  pinnipeds 
  are 
  tending 
  to 
  become 
  whales 
  or 
  that 
  a 
  typical 
  

   pinnipedian 
  ancestry 
  for 
  the 
  Cctacea 
  is 
  assumed. 
  In 
  other 
  words, 
  I 
  

   do 
  not 
  mean 
  to 
  imply 
  that 
  the 
  latter 
  have 
  been 
  evolved 
  from 
  seals, 
  but 
  

   I 
  do 
  insist 
  that 
  the 
  ancestor 
  of 
  the 
  Cctacea 
  must 
  have 
  been 
  more 
  or 
  less 
  

   seal-like 
  in 
  the 
  organization 
  of 
  the 
  hind-body 
  and 
  hind-limbs; 
  yet 
  I 
  am 
  

   not 
  at 
  all 
  certain 
  after 
  considering 
  the 
  many 
  resemblances 
  existing 
  be- 
  

   tween, 
  the 
  seals 
  and 
  whales 
  that 
  they 
  are 
  not 
  genetically 
  allied. 
  In 
  

   that 
  event 
  their 
  common 
  ancestry 
  must 
  be 
  referred 
  to 
  a 
  remote 
  period 
  

   in 
  the 
  history 
  of 
  the 
  development 
  of 
  the 
  higher 
  organic 
  types. 
  That 
  

   the 
  Cetacea 
  are 
  allied 
  through 
  descent 
  to 
  the 
  Ungitlata 
  is, 
  it 
  seems 
  to 
  

   me, 
  founded 
  on 
  far 
  less 
  convincing 
  evidence 
  than 
  the 
  assumption 
  that 
  

   they 
  are 
  affiliated 
  through 
  descent 
  with 
  the 
  terrestrial 
  and 
  amphibious 
  

   Carnivora, 
  especially 
  the 
  latter. 
  

  

  The 
  Sircnia 
  have 
  possibly 
  descended 
  from 
  a 
  quite 
  different 
  ancestral 
  

   type, 
  and 
  while 
  they 
  have 
  been 
  modified 
  in 
  an 
  analogous 
  manner, 
  so 
  far 
  

   as 
  the 
  hind 
  limbs 
  are 
  concerned, 
  they 
  present 
  every 
  evidence 
  in 
  other 
  

   respects 
  of 
  hawing 
  arisen 
  from 
  an 
  herbivorous 
  progenitor. 
  

  

  The 
  mode 
  in 
  which 
  the 
  shifting 
  of 
  the 
  hind 
  limb 
  has 
  been 
  accom- 
  

  

  