﻿[35] 
  DEVELOPMENT 
  OF 
  THE 
  CETACEA. 
  461 
  

  

  right 
  whale. 
  A 
  ruascle 
  about 
  the 
  size 
  and 
  shape 
  of 
  a 
  forefinger, 
  within 
  

   a 
  ligamentous 
  tube, 
  connected 
  the 
  thigh 
  bone 
  backwards 
  to 
  the 
  great 
  

   interpelvic 
  ligament. 
  This 
  was 
  the 
  only 
  muscular 
  structure 
  directly 
  

   connected 
  with 
  the 
  thigh 
  bone. 
  It 
  would 
  retract 
  the 
  bone. 
  The 
  fibrous 
  

   connections 
  of 
  the 
  bone 
  were 
  mainly 
  adapted 
  to 
  resist 
  outward 
  and 
  

   forward 
  traction." 
  This 
  quotation, 
  I 
  think, 
  indicates 
  quite 
  clearly 
  that 
  

   the 
  most 
  recent 
  functional 
  relations 
  of 
  the 
  muscles 
  of 
  the 
  rudimentary 
  

   thigh 
  in 
  the 
  series 
  to 
  which 
  Mcgaptcra 
  belongs 
  were 
  posterior 
  to 
  it, 
  as 
  

   in 
  fact 
  all 
  the 
  other 
  available 
  evidence 
  has 
  tended 
  to 
  show. 
  

  

  In 
  every 
  specimen 
  of 
  these 
  parts 
  from 
  Balcvna 
  figured 
  by 
  Struthers 
  

   the 
  femur 
  had 
  its 
  lower 
  end 
  swung 
  forward, 
  as 
  it 
  seems 
  the 
  femur 
  of 
  

   the 
  seals 
  usually 
  is, 
  and 
  as 
  it 
  is 
  found 
  in 
  the 
  living 
  eared 
  fissipeds 
  

   when 
  standing 
  on 
  all-fours. 
  The 
  tibial 
  rudiment, 
  on 
  the 
  other 
  hand, 
  

   lies 
  with 
  its 
  axis 
  in 
  a 
  horizontal 
  position 
  or 
  nearly, 
  such 
  as 
  is 
  assumed 
  

   by 
  that 
  bone 
  in 
  the 
  pinnipeds, 
  the 
  distal 
  apex 
  being 
  directed 
  backward 
  

   toward 
  the 
  flukes. 
  

  

  This 
  arrangement 
  of 
  the 
  limb 
  bones 
  of 
  Bakvna 
  not 
  only 
  justifies 
  to 
  a 
  

   great 
  extent 
  the 
  views 
  here 
  assumed 
  as 
  to 
  the 
  nature 
  of 
  the 
  flukes, 
  but 
  

   also 
  that 
  of 
  Struthers, 
  w 
  7 
  ho, 
  on 
  the 
  basis 
  of 
  his 
  observations 
  on 
  the 
  rudi- 
  

   mentary 
  finger- 
  muscles 
  of 
  Megaptcra 
  longimana,* 
  concludes 
  that 
  the 
  

   Cetacea 
  have 
  descended 
  from 
  a 
  form 
  in 
  which 
  limbs 
  were 
  much 
  better 
  or 
  

   functionally 
  developed; 
  an 
  opinion 
  also 
  entertained 
  by 
  Flower. 
  Such 
  

   a 
  conclusion 
  is 
  also 
  justified 
  by 
  the 
  existence 
  of 
  synovial 
  bursas 
  between 
  

   the 
  head 
  of 
  the 
  femur 
  and 
  the 
  pelvic 
  bone 
  and 
  between 
  the 
  femur 
  and 
  

   tibia 
  of 
  Balcena, 
  according 
  to 
  the 
  former 
  author's 
  observations. 
  

  

  I 
  think, 
  indeed, 
  we 
  may 
  go 
  a 
  step 
  farther 
  and 
  declare 
  with 
  perfect 
  

   safety 
  that 
  inasmuch 
  as 
  only 
  the 
  proximal 
  end 
  of 
  the 
  tibia 
  is 
  developed 
  

   mBakcna 
  as 
  a 
  degenerate 
  element, 
  which 
  is 
  not 
  even 
  ossified, 
  and 
  which 
  

   has 
  its 
  distal 
  end 
  pointing 
  backwards, 
  the 
  tibia, 
  if 
  fully 
  developed 
  and 
  

   extended 
  posteriorly 
  to 
  its 
  normal 
  length 
  as 
  found 
  in 
  other 
  mammals, 
  

   or 
  as 
  in 
  the 
  seals 
  with 
  the 
  tarsus 
  superimposed 
  upon 
  its 
  distal 
  extrem- 
  

   ity, 
  it 
  must 
  be 
  evident 
  to 
  every 
  reasonable 
  morphologist 
  that 
  the 
  limb 
  

   or 
  pes 
  would 
  not 
  be 
  extended 
  outward 
  laterally 
  from 
  the 
  body 
  in 
  a 
  

   transverse 
  vertical 
  plane 
  with 
  the 
  acetabulum, 
  as 
  is 
  the 
  case 
  in 
  terres- 
  

   trial 
  mammals, 
  but 
  would 
  be 
  extended 
  back 
  horizontally 
  from 
  the 
  lower 
  

   end 
  of 
  the 
  femur 
  as 
  in 
  the 
  seals, 
  and 
  the 
  limb 
  not 
  become 
  outwardly 
  

   apparent 
  until 
  some 
  distance 
  behind 
  the 
  vertical 
  line 
  drawn 
  through 
  the 
  

   hip-joint. 
  It 
  thus 
  becomes 
  obvious 
  that 
  translocation 
  of 
  the 
  distal 
  part 
  

   of 
  the 
  pelvic 
  limbs 
  of 
  cetaceans 
  has 
  positively 
  taken 
  place, 
  or, 
  in 
  other 
  

   words, 
  that 
  the 
  crural, 
  tarsal, 
  and 
  phalangeal 
  parts 
  of 
  these 
  limbs 
  have 
  

   been 
  rotated 
  backward, 
  and 
  included 
  from 
  before 
  backward 
  by 
  the 
  in- 
  

   teguments 
  as 
  in 
  the 
  seals. 
  This 
  inclusion, 
  however, 
  has 
  probably 
  been 
  

   even 
  more 
  complete 
  in 
  cetaceans 
  than 
  in 
  pinnipeds 
  as 
  a 
  consequence 
  of 
  

   disuse 
  of 
  the 
  still 
  exserted 
  feet 
  as 
  ambulatory 
  organs 
  and 
  their 
  utiliza- 
  

  

  * 
  See 
  American 
  Naturalist, 
  Feb., 
  1885, 
  XIX, 
  pp. 
  126, 
  127. 
  

  

  