﻿478 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  [52] 
  

  

  first 
  stages 
  of 
  the 
  development 
  of 
  the 
  vertebrate 
  limb. 
  In 
  other 
  words, 
  

   the 
  general 
  law 
  that 
  the 
  first 
  stage 
  of 
  limb-growth 
  to 
  be 
  evolved 
  by 
  the 
  

   class 
  is 
  the 
  last 
  to 
  disappear 
  is 
  here 
  most 
  emphatically 
  confirmed 
  by 
  the 
  

   development 
  of 
  the 
  backwardly 
  translocated 
  distal 
  vestiges 
  of 
  the 
  limbs 
  

   of 
  sirenians. 
  

  

  The 
  argument 
  from 
  Pteronura 
  here 
  also 
  utterly 
  fails 
  to 
  be 
  satisfactory 
  

   because 
  the 
  terminal 
  exserted 
  end 
  of 
  the 
  tail 
  of 
  the 
  foetus 
  of 
  the 
  Mana- 
  

   tee 
  shows 
  that 
  the 
  limb 
  folds 
  are 
  truly 
  to 
  be 
  considered 
  lateral 
  as 
  in 
  

   other 
  vertebrates, 
  and 
  are 
  not 
  evolved 
  from 
  a 
  continuous 
  marginal 
  cau- 
  

   dal 
  ridge 
  or 
  fold 
  extending 
  along 
  the 
  whole 
  length 
  of 
  the 
  tail, 
  but 
  from 
  

   short 
  folds 
  representing 
  limb 
  rudiments 
  which 
  have 
  been 
  derived 
  from 
  

   functional 
  limbs. 
  

  

  A 
  consideration 
  of 
  the 
  muscular 
  system 
  is 
  important 
  in 
  its 
  bearings 
  

   upon 
  my 
  hypothesis, 
  so 
  it 
  will 
  be 
  desirable 
  to 
  cite 
  Marie's 
  * 
  observa- 
  

   tions 
  on 
  the 
  muscles 
  of 
  this 
  region 
  of 
  the 
  Manatee. 
  We 
  will 
  first 
  note 
  

   the 
  dorsal 
  muscles 
  of 
  the 
  tail, 
  or 
  those 
  lying 
  above 
  the 
  vertebral 
  col- 
  

   umn. 
  

  

  "What 
  corresponds 
  to 
  the 
  combined 
  or 
  continuous 
  spinalis 
  dorsi 
  and 
  

   levator 
  caudcc 
  interims 
  is 
  a 
  long, 
  narrow, 
  but 
  in 
  the 
  back 
  vertically, 
  deep 
  

   muscle, 
  which 
  runs 
  from 
  the 
  neck 
  backwards 
  as 
  far 
  as 
  the 
  end 
  of 
  the 
  

   tail. 
  Anteriorly, 
  where 
  laterally 
  compressed 
  but 
  fleshy, 
  it 
  fills 
  vertically 
  

   the 
  hollow 
  between 
  the 
  cervical 
  spines 
  and 
  transverse 
  processes. 
  Pos- 
  

   teriorly 
  it 
  becomes 
  tendinous 
  and 
  aponeurotic, 
  and 
  is 
  fastened 
  to 
  the 
  

   caudal 
  vertebrae 
  superiorly. 
  

  

  " 
  There 
  is 
  a 
  massive 
  and 
  in 
  great 
  part 
  fleshy 
  longissimus 
  dorsi, 
  which 
  

   extends 
  outside 
  the 
  last 
  from 
  the 
  first 
  rib 
  backwards 
  to 
  the 
  very 
  end 
  of 
  

   the 
  caudal 
  vertebrae, 
  thus 
  including 
  what 
  constitutes 
  the 
  levator 
  caudoe 
  

   externus 
  of 
  most 
  other 
  mammals. 
  Like 
  the 
  preceding, 
  the 
  tail-tendons 
  

   are 
  interwoven 
  into 
  an 
  aponeurosis, 
  partially 
  fixed 
  to 
  the 
  transverse 
  

   and 
  to 
  the 
  spinous 
  processes." 
  (Op. 
  cit., 
  p. 
  141.) 
  

  

  The 
  ventral 
  or 
  hyposkeletal, 
  lumbo-caudal 
  system 
  is 
  not 
  prolonged 
  

   so 
  far 
  forwards, 
  and 
  has 
  a 
  posterior 
  insertion 
  different 
  from 
  the 
  dorsal 
  

   set. 
  

  

  <■' 
  The 
  first 
  and 
  notable 
  muscle 
  is 
  that 
  which 
  in 
  the 
  profile 
  and 
  uuder- 
  

   view 
  appears 
  as 
  a 
  great 
  and 
  only 
  mass 
  filling 
  the 
  interval 
  between 
  the 
  

   last 
  rib 
  and 
  the 
  caudal 
  extremity 
  and 
  the 
  space 
  between 
  the 
  chevron 
  

   bones 
  and 
  the 
  tips 
  of 
  the 
  lumbo-caudal 
  transverse 
  processes. 
  This 
  as- 
  

   pect 
  is 
  in 
  some 
  respects 
  deceptive, 
  as 
  the 
  muscle, 
  when 
  manipulated 
  by 
  

   the 
  scalpel, 
  is 
  found 
  to 
  be 
  only 
  one 
  of 
  two 
  thick 
  and 
  long 
  layers 
  occu- 
  

   pying 
  the 
  area 
  in 
  question. 
  The 
  superficial 
  stratum 
  or 
  musculo-tendi- 
  

   nous 
  lamella 
  arises 
  from 
  the 
  outer 
  half 
  and 
  inferior 
  surface 
  of 
  the 
  last 
  

   rib, 
  being 
  here 
  partially 
  overlain 
  by 
  the 
  external 
  oblique 
  and 
  panni- 
  

   culus 
  ; 
  thence, 
  with 
  inwardly 
  oblique 
  fibers, 
  it 
  is 
  inserted 
  mesially 
  from 
  

   the 
  third 
  chevron 
  bone 
  backwards 
  to 
  the 
  termination 
  of 
  the 
  spinal 
  col- 
  

  

  * 
  Ou 
  the 
  form 
  and 
  structure 
  of 
  the 
  manatee, 
  by 
  Dr. 
  James 
  Marie, 
  Trans. 
  Zool. 
  Soc. 
  

   London, 
  VIII, 
  1874, 
  pp. 
  127-202, 
  pis. 
  17-26. 
  

  

  