﻿[43] 
  DEVELOPMENT 
  OF 
  THE 
  CETACEA. 
  4g9 
  

  

  thern 
  as 
  interhaerno-spinales, 
  this 
  term 
  being 
  more 
  in 
  accordance 
  with 
  

   morphological 
  anatomy. 
  Stannius 
  likewise 
  differentiates 
  and 
  names 
  as 
  

   m. 
  interaccessorii 
  a 
  number 
  of 
  tendiuo-fleshy 
  fascicles 
  which 
  intervene 
  

   between 
  the 
  one 
  and 
  the 
  other 
  accessory 
  spinous 
  processes 
  of 
  the 
  lum- 
  

   bar 
  and 
  dorsal 
  vertebra?, 
  in 
  a 
  longitudinal 
  direction. 
  These 
  have 
  not 
  

   been 
  observed 
  by 
  me, 
  but 
  I 
  am 
  inclined 
  to 
  regard 
  them 
  as 
  intermeta- 
  

   pophysiales." 
  

  

  As 
  already 
  urged 
  there 
  can 
  be 
  no 
  doubt 
  of 
  the 
  fact 
  that 
  the 
  great 
  iu- 
  

   fracaudal 
  or 
  hyposkeletal 
  muscles 
  of 
  the 
  tail 
  of 
  cetaceans 
  are 
  in 
  part 
  

   homologous 
  with 
  the 
  psoas 
  major 
  and 
  minor 
  of 
  quadrupeds. 
  In 
  fact, 
  the 
  

   inlracaudal 
  and 
  sacro-coccygeus 
  of 
  Murie 
  are 
  but 
  a 
  system 
  of 
  psoas 
  

   muscles 
  prolonged 
  rearwards 
  together 
  with 
  caudal 
  muscles, 
  and 
  de- 
  

   veloped 
  to 
  an 
  extent 
  not 
  encountered 
  in 
  other 
  types. 
  The 
  quadratus 
  

   lumborum 
  may 
  also 
  be 
  represented. 
  Whatever 
  is 
  the 
  truth 
  as 
  to 
  the 
  

   exact 
  homologies 
  of 
  these 
  muscles, 
  a 
  fact 
  which 
  will 
  not 
  have 
  escaped 
  

   the 
  critical 
  reader's 
  attention, 
  is 
  Murie's 
  mention 
  of 
  the 
  final 
  direct 
  and 
  

   indirect 
  insertion 
  of 
  the 
  tendons 
  of 
  the 
  caudal 
  musculature 
  into 
  the 
  

   flukes. 
  The 
  psoas 
  being 
  represented 
  in 
  the 
  hyposkeletal 
  musculature 
  

   is 
  thus 
  found 
  to 
  have 
  had 
  its 
  insertion 
  greatly 
  shifted 
  in 
  a 
  posterior 
  di- 
  

   rection 
  so 
  as 
  to 
  act 
  upon 
  the 
  flukes 
  — 
  degenerate 
  pedes 
  of 
  Cetacea 
  — 
  in- 
  

   stead 
  of 
  upon 
  the 
  lesser 
  trochanter 
  of 
  the 
  femur 
  as 
  in 
  normal 
  forms. 
  

   We 
  thus 
  find 
  that 
  the 
  backward 
  translocation 
  of 
  the 
  muscular 
  inser- 
  

   tions 
  of 
  the 
  limb 
  muscles 
  which 
  began 
  in 
  a 
  seal-like 
  type 
  has 
  reached 
  

   its 
  extremest 
  expression 
  in 
  the 
  whales, 
  in 
  which 
  we 
  can 
  with 
  certainty, 
  

   however, 
  assume 
  this 
  much 
  of 
  what 
  is 
  in 
  reality 
  part 
  only 
  of 
  the 
  psoas 
  

   of 
  land 
  forms, 
  in 
  which 
  it 
  is 
  usually 
  inserted 
  into 
  the 
  femur. 
  

  

  This 
  tendency 
  towards 
  a 
  backward 
  extension 
  of 
  its 
  insertion 
  is 
  also 
  

   obvious, 
  for 
  instance, 
  in 
  the 
  rectus 
  abdominis. 
  Murie* 
  remarks 
  of 
  it 
  : 
  

   " 
  The 
  rectus 
  abdominis, 
  which 
  I 
  have 
  already 
  described, 
  partly 
  mingles 
  

   with 
  the 
  generative 
  muscles, 
  inasmuch 
  as 
  its 
  posterior 
  narrowed 
  ex- 
  

   tremity 
  and 
  terminal 
  tendon 
  enclasp 
  the 
  deeper 
  fleshy 
  structures 
  of 
  the 
  

   vulva 
  and 
  winds 
  round 
  each 
  innominate 
  bone, 
  finally 
  being 
  inserted 
  into 
  

   the 
  neighborhood 
  of 
  the 
  chevron 
  bones." 
  

  

  VI. 
  — 
  The 
  lumbo 
  caudal 
  plexus 
  of 
  nerves 
  in 
  cetaceans. 
  

  

  The 
  only 
  published 
  account 
  of 
  the 
  posterior 
  part 
  of 
  the 
  spinal 
  nervous 
  

   system 
  of 
  cetaceans 
  which 
  I 
  have 
  been 
  able 
  to 
  find 
  and 
  which 
  is 
  at 
  all 
  

   complete, 
  is 
  that 
  given 
  by 
  D. 
  J. 
  Cunningham, 
  based 
  on 
  dissections 
  of 
  

   the 
  porpoise 
  and 
  dolphin.f 
  In 
  the 
  porpoise, 
  Cunningham 
  found 
  that 
  

   the 
  spinal 
  cord 
  extends 
  from 
  the 
  foramen 
  magnum 
  to 
  the 
  interval 
  be- 
  

   tween 
  the 
  sixth 
  and 
  seventh 
  lumbo-caudal 
  vertebra?, 
  and 
  ends 
  opposite 
  

   the 
  foramina 
  giving 
  exit 
  to 
  the 
  twenty-seventh 
  pair 
  of 
  spinal 
  nerves. 
  

  

  * 
  Op. 
  c;7.,p. 
  288. 
  

  

  t 
  The 
  spinal 
  nervous 
  system 
  of 
  the 
  porpoise 
  and 
  dolphin. 
  Journ. 
  Anat. 
  and 
  Physiol., 
  

   XI, 
  pp. 
  '209-228, 
  Plate 
  VII. 
  

  

  