﻿32 
  DR. 
  G. 
  C. 
  BOURNE 
  ON 
  THE 
  RANIN1D.E 
  : 
  

  

  less 
  with 
  the 
  Crayfishes, 
  because 
  in 
  the 
  first-named 
  the 
  thoracic 
  connectives 
  

   are 
  separate 
  and 
  show 
  hut 
  little 
  tendency 
  to 
  lateral 
  fusion. 
  But 
  of 
  all 
  the 
  

   Macrura 
  thev 
  most 
  closely 
  resemble 
  Nephrops 
  in 
  tins 
  and 
  other 
  respects. 
  

   In 
  both 
  the 
  suboesophageal 
  ganglion 
  mass 
  is 
  in 
  a 
  very 
  similar 
  state 
  of 
  con- 
  

   centration, 
  the 
  differences 
  being 
  that 
  in 
  Ranina 
  the 
  mandibular 
  nerves 
  are 
  

   given 
  off 
  from 
  the 
  circum-cesophageal 
  connectives 
  (this 
  may 
  be 
  correlated 
  

   with 
  the 
  great 
  length 
  of 
  these 
  connectives) 
  and 
  in 
  Nephrops 
  the 
  ganglion 
  

   pair 
  of 
  the 
  third 
  maxillipeds 
  retain 
  a 
  certain 
  distinctness. 
  The 
  connectives 
  

   between 
  the 
  suboesophageal 
  and 
  the 
  ganglion-pair 
  of 
  the 
  chelipeds 
  are 
  very 
  

   nearly 
  of 
  the 
  same 
  length 
  and 
  in 
  the 
  same 
  condition 
  of 
  incipient 
  lateral 
  

   fusion 
  in 
  Nephrops 
  as 
  in 
  Notopus, 
  though 
  the 
  concentration 
  is 
  carried 
  further 
  

   in 
  the 
  lateral 
  sense 
  in 
  Lyreidus 
  and 
  in 
  the 
  longitudinal 
  sense 
  in 
  Ranina. 
  

   The 
  connectives 
  between 
  the 
  ganglion-pairs 
  of 
  the 
  chelipeds 
  and 
  first 
  

   pereiopods 
  are 
  much 
  longer 
  in 
  the 
  Raninidse 
  than 
  in 
  Nephrops, 
  but 
  are 
  

   equally 
  distinctly 
  paired 
  in 
  both 
  and 
  show 
  no 
  tendency 
  to 
  lateral 
  fusion. 
  

   The 
  same 
  may 
  be 
  said 
  of 
  the 
  connectives 
  next 
  following. 
  In 
  the 
  Raninidse 
  

   the 
  last 
  two 
  thoracic 
  ganglion-pairs 
  are 
  more 
  {Lyreidus) 
  or 
  less 
  {Ranina) 
  

   closely 
  fused 
  together. 
  These 
  differences 
  apart, 
  if 
  the 
  long 
  chain 
  of 
  six 
  

   abdominal 
  ganglion-pairs 
  of 
  Nephrops 
  were 
  shortened 
  up 
  to 
  the 
  condition 
  

   found 
  in 
  the 
  Raninidse 
  and 
  withdrawn 
  into 
  the 
  thorax, 
  there 
  would 
  be 
  very 
  

   little 
  difference 
  between 
  the 
  two 
  nervous 
  systems. 
  So 
  far, 
  then, 
  as 
  this 
  part 
  

   of 
  their 
  anatomy 
  may 
  serve 
  as 
  a 
  guide, 
  the 
  Dromiacea 
  have 
  progressed 
  

   further 
  from 
  the 
  Macrurous 
  in 
  the 
  direction 
  of 
  the 
  Brachyurous 
  type 
  than 
  

   have 
  the 
  Raninidse, 
  but 
  the 
  latter 
  retain 
  many 
  distinct 
  Macrurous 
  features 
  

   and 
  exhibit 
  specially 
  close 
  affinities 
  with 
  Nephrops. 
  

  

  It 
  will 
  be 
  noticed 
  that 
  there 
  is 
  a 
  marked 
  tendency 
  for 
  the 
  thoracic 
  ganglia 
  

   to 
  form 
  two 
  groups, 
  one 
  at 
  the 
  anterior 
  the 
  other 
  at 
  the 
  posterior 
  end 
  of 
  the 
  

   thorax, 
  in 
  the 
  Raninidse. 
  This 
  must 
  be 
  correlated 
  with 
  the 
  powerful 
  develop- 
  

   ment 
  of 
  the 
  first, 
  second, 
  and 
  third 
  pereiopods 
  as 
  digging 
  or 
  swimming 
  

   organs. 
  These 
  limbs 
  are 
  exceedingly 
  strong, 
  and 
  are 
  actuated 
  by 
  largely 
  

   developed 
  muscles 
  enclosed 
  in 
  remarkably 
  deep 
  cavities 
  formed 
  by 
  the 
  endo- 
  

   phragmal 
  skeleton. 
  The 
  size 
  and 
  extent 
  of 
  these 
  muscle 
  cavities 
  as 
  compared 
  

   with 
  those 
  of 
  other 
  Brachyura 
  is 
  one 
  of 
  the 
  most 
  striking 
  features 
  when 
  one 
  

   undertakes 
  a 
  dissection 
  of 
  any 
  member 
  of 
  the 
  Raninidse, 
  and 
  the 
  abundant 
  

   musculature 
  of 
  the 
  limbs 
  makes 
  the 
  dissection 
  of 
  the 
  nervous 
  system 
  difficult. 
  

   It 
  is 
  also 
  worthy 
  of 
  remark 
  that 
  in 
  Lyreidus 
  the 
  last 
  pair 
  of 
  pereiopods 
  are 
  

   very 
  weak 
  and 
  attenuated 
  and 
  the 
  corresponding 
  ganglion-pair 
  is 
  practically 
  

   unrecognizable, 
  whereas 
  in 
  Ranina, 
  in 
  which 
  the 
  last 
  pair 
  of 
  pereiopods 
  

   differs 
  little 
  in 
  size 
  from 
  the 
  rest, 
  its 
  ganglion-pair 
  is 
  distinct 
  and 
  emits 
  

   large 
  nerves 
  to 
  the 
  limbs. 
  

  

  Two 
  good 
  figures 
  are 
  given 
  in 
  Cuvier's 
  ' 
  Regne 
  Animal,' 
  but 
  otherwise 
  

   de 
  Haan 
  is 
  the 
  only 
  author 
  who 
  has 
  dealt 
  with 
  the 
  endophragmal 
  skeleton 
  of 
  

  

  