﻿[15] 
  DEVELOPMENT 
  OF 
  THE 
  CETACEA. 
  441 
  

  

  it, 
  are 
  short 
  and 
  only 
  pass 
  out 
  to 
  about 
  as 
  far 
  as 
  the 
  basal 
  third 
  of 
  the 
  

   fluke. 
  In 
  all 
  there 
  are 
  42 
  vessels 
  supplying 
  the 
  flukes, 
  21 
  to 
  each 
  side, 
  

   and 
  they 
  correspond 
  only 
  partially 
  with 
  the 
  number 
  of 
  vertebral 
  seg- 
  

   ments, 
  of 
  which 
  as 
  many 
  as 
  fifteen 
  may 
  be 
  included 
  between 
  the 
  bases 
  

   of 
  the 
  flukes 
  of 
  opposite 
  sides. 
  This 
  is 
  the 
  arrangement 
  in 
  Phocama, 
  

   and 
  it 
  is 
  doubtless 
  similar 
  in 
  other 
  forms. 
  The 
  superficial 
  and 
  not 
  axial 
  

   position 
  of 
  the 
  vessels 
  is 
  a 
  striking 
  peculiarity 
  and 
  is 
  very 
  different 
  from 
  

   the 
  arrangement 
  of 
  the 
  blood 
  supply 
  of 
  the 
  dorsal 
  fin, 
  as 
  elsewhere 
  de- 
  

   scribed. 
  

  

  The 
  arrangement 
  of 
  the 
  vascular 
  supply 
  of 
  the 
  flukes 
  thus 
  affords 
  a 
  

   strong 
  argument 
  in 
  favor 
  of 
  the 
  view 
  which 
  I 
  have 
  defended, 
  viz, 
  that 
  

   the 
  flukes 
  are 
  tbe 
  homologues 
  of 
  feet 
  and 
  not 
  special 
  lateral 
  integument- 
  

   ary 
  outgrowths. 
  On 
  the 
  hypothesis 
  that 
  the 
  flukes 
  are 
  mainly 
  homolo- 
  

   gous 
  with 
  a 
  pes, 
  or 
  perhaps 
  the 
  digital 
  part 
  of 
  a 
  pes, 
  there 
  ovght 
  to 
  be 
  

   about 
  ten 
  vessels 
  present 
  on 
  the 
  dorsal 
  and 
  as 
  many 
  on 
  the 
  ventral 
  

   side 
  of 
  tbe 
  flukes 
  representing 
  the 
  paired 
  interdigital 
  arteries, 
  of 
  which 
  

   there 
  are 
  two 
  pairs 
  to 
  each 
  digit 
  in 
  the 
  manus, 
  as 
  well 
  as 
  pes 
  of 
  normal 
  

   mammals. 
  In 
  the 
  foot 
  of 
  the 
  latter 
  these 
  arise 
  from 
  the 
  dorsalis 
  pedis 
  

   on 
  the 
  dorsal 
  side 
  and 
  from 
  the 
  external 
  and 
  internal 
  plantar 
  artery 
  on 
  

   the 
  ventral 
  side. 
  This 
  close 
  correspondence 
  between 
  the 
  normal 
  num- 
  

   ber 
  of 
  dorsal 
  and 
  ventral 
  interdigital 
  arteries 
  in 
  normal 
  forms 
  and 
  those 
  

   found 
  in 
  the 
  flukes 
  of 
  Getacea 
  is, 
  to 
  say 
  the 
  least, 
  suggestive, 
  though 
  

   it 
  must.be 
  admitted 
  that 
  it 
  cannot 
  be 
  proved 
  that 
  they 
  arise 
  in 
  the 
  

   Getacea 
  from 
  the 
  femoral 
  and 
  popliteal 
  continuations 
  of 
  the 
  external 
  

   iliac, 
  but 
  have 
  acquired 
  a 
  new 
  origin 
  from 
  the 
  caudal 
  continuation 
  of 
  

   the 
  aorta 
  and 
  its 
  dorsal 
  branches 
  serially 
  homologous 
  with 
  intercostal 
  

   arteries 
  anteriorly. 
  

  

  The 
  arrangement 
  of 
  the 
  principal 
  and 
  deeper 
  vessels 
  of 
  the 
  manus 
  

   of 
  Phocccna 
  I 
  have 
  not 
  investigated, 
  but 
  it 
  has 
  struck 
  me 
  as 
  being 
  very 
  

   remarkable 
  that 
  the 
  distal 
  third 
  of 
  the 
  manus 
  should 
  be 
  supplied 
  by 
  

   longitudinal 
  vascular 
  trunks 
  lying 
  between 
  the 
  second 
  and 
  third 
  digits, 
  

   these 
  trunks 
  giving 
  off 
  lateral 
  twigs 
  on 
  either 
  side 
  to 
  supply 
  the 
  whole 
  

   of 
  the 
  terminal 
  third 
  of 
  the 
  flipper 
  or 
  manus, 
  just 
  as 
  the 
  distal 
  two- 
  

   thirds 
  of 
  the 
  flukes 
  are 
  supplied 
  by 
  the 
  long 
  fourth 
  dorsal 
  and 
  ventral 
  

   arterial 
  trunks, 
  which, 
  like 
  the 
  distal 
  trunks 
  in 
  the 
  former, 
  give 
  off 
  

   lateral 
  twigs, 
  which 
  run 
  to 
  the 
  anterior 
  and 
  posterior 
  borders 
  of 
  the 
  

   flukes. 
  This 
  arrangement 
  of 
  vessels 
  in 
  both 
  seems 
  to 
  me 
  to 
  indicate 
  

   more 
  than 
  a 
  mere 
  analogical 
  resemblance; 
  that, 
  in 
  fact, 
  the 
  two 
  princi- 
  

   pal 
  trunks 
  of 
  the 
  fluke 
  are 
  the 
  interdigital 
  vessels 
  which 
  were 
  most 
  

   strongly 
  developed 
  alongside 
  of 
  the 
  longest, 
  probably 
  the 
  second 
  digit 
  

   of 
  the 
  pes, 
  before 
  the 
  phalanges 
  of 
  the 
  others 
  began 
  to 
  atrophy. 
  

  

  Murie* 
  figures 
  the 
  principal 
  superficial 
  ventral 
  vessel 
  of 
  the 
  flukes 
  of 
  

   .Globiocephalus. 
  but 
  does 
  not 
  show 
  the 
  accessory 
  shorter 
  ones 
  running 
  

   parallel 
  with 
  it 
  in 
  front 
  and 
  behind 
  its 
  proximal 
  end. 
  Here, 
  as 
  in 
  Pho- 
  

  

  * 
  On 
  tlio 
  organization 
  of 
  tho 
  Caaing 
  whale, 
  Globiocephalus 
  viclcts. 
  Trans. 
  Zool. 
  Soc. 
  

   London, 
  VIII, 
  1874, 
  pp, 
  235-301 
  (fig. 
  58, 
  pi. 
  3f»). 
  

  

  