﻿34 
  DR. 
  G. 
  0. 
  BOURNE 
  ON 
  THE 
  RANINID.E: 
  

  

  apodeme 
  seems 
  to 
  end 
  just 
  below 
  the 
  articular 
  knob 
  : 
  in 
  reality 
  it 
  is 
  prolonged 
  

   beyond 
  it, 
  and 
  can 
  be 
  traced 
  along 
  the 
  inner 
  and 
  hinder 
  edge 
  of 
  the 
  twisted 
  

   lamella 
  or 
  arthrophragm 
  that 
  separates 
  each 
  articular 
  cavity 
  from 
  the 
  one 
  

   next 
  behind 
  it. 
  The 
  arthrophragm. 
  in 
  fact, 
  is 
  a 
  double 
  fold 
  of 
  the 
  cuticle 
  or 
  

   apodeme, 
  continuous 
  with 
  the 
  pleural 
  apodeme 
  ; 
  the 
  two 
  edges 
  of 
  the 
  fold 
  

   run 
  down 
  rather 
  to 
  the 
  inside 
  of 
  the 
  hinder 
  edge 
  of 
  the 
  arthrophragm, 
  and 
  in 
  

   the 
  entire 
  animal 
  pass 
  respectively 
  into 
  the 
  arthrodial 
  or 
  joint 
  membrane 
  of 
  

   the 
  limb 
  in 
  front 
  and 
  the 
  limb 
  behind. 
  At 
  the 
  lower 
  end 
  of 
  the 
  arthrophragm 
  

   the 
  groove 
  forms 
  the 
  apparent 
  boundary 
  between 
  the 
  contiguous 
  sterna, 
  

   but 
  here 
  again 
  there 
  is 
  no 
  suture 
  ; 
  the 
  sterna 
  are 
  really 
  continuous, 
  and 
  

   are 
  only 
  separated 
  by 
  apodemes. 
  All 
  this 
  is 
  familiar, 
  but 
  as 
  separate 
  names, 
  

   epimera, 
  sterna, 
  arthrophragms, 
  etc., 
  are 
  given 
  to 
  the 
  various 
  parts, 
  I 
  have 
  

   thought 
  it 
  desirable, 
  in 
  view 
  of 
  the 
  comparisons 
  that 
  are 
  to 
  follow, 
  to 
  emphasize 
  

   the 
  fact 
  that 
  these 
  names 
  only 
  apply 
  to 
  local 
  areas 
  and 
  indurations 
  separated 
  

   from 
  one 
  another 
  by 
  more 
  or 
  less 
  deep 
  infoldings 
  of 
  a 
  continuous 
  cuticle. 
  

   In 
  the 
  upper 
  and 
  lower 
  parts 
  of 
  the 
  arthrophragm 
  its 
  apodeme 
  is 
  shallow, 
  and 
  

   consequently 
  the 
  arthrophragmal 
  partition 
  extends 
  only 
  a 
  little 
  way 
  into 
  the 
  

   cavity 
  of 
  the 
  body 
  ; 
  but 
  at 
  about 
  the 
  middle 
  of 
  its 
  course 
  the 
  apodeme 
  

   becomes 
  very 
  deep 
  and 
  gives 
  rise 
  to 
  a 
  lamina 
  running 
  upwards, 
  forwards, 
  

   and 
  inwards 
  towards 
  the 
  middle 
  line, 
  short 
  of 
  which 
  it 
  expands 
  into 
  

   horizontally 
  flattened 
  plate 
  with 
  jagged 
  edges, 
  which 
  makes 
  more 
  or 
  less 
  

   intimate 
  union 
  with 
  its 
  fellow 
  of 
  the 
  opposite 
  side. 
  The 
  lalninse 
  in 
  question 
  

   are 
  the 
  endosternites 
  : 
  they 
  and 
  their 
  flattened 
  summits 
  form 
  the 
  walls 
  and 
  

   roof 
  of 
  the 
  so-called 
  sternal 
  canal 
  within 
  which 
  the 
  thoracic 
  nerve-ganglion 
  

   chain 
  lies. 
  A 
  sternal 
  canal 
  is 
  found 
  in 
  the 
  Macrura 
  reptantia 
  and 
  in 
  some 
  

   Anomura, 
  but, 
  with 
  the 
  exception 
  of 
  the 
  Raninidse, 
  it 
  does 
  not 
  occur 
  in 
  the 
  

   Brachyura. 
  PI. 
  4. 
  fig. 
  11 
  also 
  shows 
  the 
  epimeral 
  apodemes 
  or 
  endopleurites. 
  

   As 
  the 
  articular 
  cavities 
  slant 
  backwards, 
  the 
  endopleurites 
  alternate 
  in 
  

   position 
  with 
  the 
  endosternites, 
  and, 
  as 
  is 
  familiarly 
  known, 
  each 
  endopleurite 
  

   divides 
  internally, 
  sending 
  a 
  posterior 
  branch 
  to 
  unite 
  with 
  the 
  endosternite 
  

   of 
  the 
  segment 
  behind, 
  an 
  anterior 
  branch 
  to 
  unite 
  with 
  the 
  endosternite 
  in 
  

   front. 
  The 
  result 
  of 
  all 
  these 
  complicated 
  arrangements 
  is 
  that 
  the 
  cavity 
  of 
  

   each 
  limb 
  communicates 
  internally 
  with 
  two 
  imperfectly 
  delimited 
  chambers, 
  

   which 
  may 
  properly 
  be 
  called 
  muscle-cavities 
  as 
  the 
  abductor 
  and 
  adductor 
  

   muscles 
  of 
  the 
  limbs 
  are 
  attached 
  to 
  the 
  several 
  apodemic 
  ingrowths 
  that 
  

   constitute 
  their 
  walls. 
  In 
  the 
  Macrura, 
  as 
  the 
  articular 
  sockets 
  of 
  the 
  limbs 
  

   look 
  nearly 
  ventrally 
  and 
  the 
  epimera 
  are 
  not 
  much 
  inclined 
  inwards 
  from 
  

   the 
  vertical, 
  the 
  muscle-cavities 
  lie 
  in 
  nearly 
  the 
  same 
  horizontal 
  plane 
  and 
  

   alternate 
  with 
  one 
  another. 
  A 
  consideration 
  of 
  the 
  relative 
  positions 
  of 
  the 
  

   dorsal 
  strophingia 
  and 
  ventral 
  strophidia 
  by 
  which 
  the 
  coxa 
  of 
  the 
  limb 
  is 
  

   hinged 
  to 
  the 
  articular 
  frame 
  will 
  show 
  that 
  the 
  outermost 
  and 
  slightly 
  

   dorsal 
  of 
  the 
  two 
  muscle-cavities 
  encloses 
  the 
  abductor 
  muscles 
  whose 
  action 
  

  

  