﻿?,0 
  DR. 
  0. 
  C. 
  BOURNE 
  ON 
  THE 
  RANINID.E 
  : 
  

  

  The 
  succeeding 
  ganglion 
  pair, 
  supplying 
  the 
  first 
  pereiopods, 
  is 
  situated 
  well 
  

   back 
  in 
  the 
  thorax, 
  and 
  is 
  connected 
  with 
  the 
  pair 
  supplying 
  the 
  chelipeds 
  by 
  

   two 
  long 
  connectives 
  separated 
  from 
  one 
  another 
  by 
  a 
  well-marked 
  interval. 
  

   The 
  ganglion-pair 
  of 
  the 
  second 
  pereiopods 
  is 
  united 
  with 
  the 
  preceding 
  pair 
  

   by 
  similarly 
  distinct 
  connectives, 
  but 
  only 
  one-third 
  as 
  long- 
  as 
  those 
  con- 
  

   necting 
  the 
  chelipeds 
  and 
  first 
  pair. 
  The 
  connectives 
  between 
  the 
  second 
  

   and 
  third 
  ganglion-pairs 
  of 
  the 
  pereiopods 
  are 
  shorter, 
  but 
  set 
  widely 
  apart, 
  

   leaving 
  an 
  oval 
  space 
  for 
  the 
  passage 
  of 
  the 
  large 
  sternal 
  artery. 
  The 
  two 
  

   last 
  thoracic 
  ganglion-pairs, 
  supplying 
  the 
  third 
  and 
  fourth 
  pereiopods, 
  are 
  

   fused 
  together, 
  and 
  the 
  connections 
  between 
  them 
  cannot 
  be 
  distinguished, 
  

   but 
  the 
  separate 
  ganglia 
  can 
  be 
  clearly 
  recognized. 
  Olosely 
  applied 
  to 
  the 
  

   last 
  thoracic 
  ganglion-pair 
  is 
  the 
  chain 
  of 
  abdominal 
  ganglia, 
  completely 
  

   withdrawn 
  into 
  the 
  thorax 
  and 
  represented 
  by 
  a 
  short 
  and 
  thick 
  nervous 
  mass 
  

   divided 
  by 
  distinct 
  transverse 
  constrictions 
  into 
  five 
  segments. 
  The 
  terminal 
  

   segment 
  apparently 
  represents 
  the 
  fifth 
  and 
  sixth 
  abdominal 
  ganglia 
  fused 
  

   together. 
  Paired 
  nerves 
  issue 
  from 
  each 
  abdominal 
  ganglionic 
  segment, 
  and 
  

   pass 
  backwards 
  closely 
  bound 
  up 
  in 
  the 
  same 
  connective-tissue 
  sheath 
  as 
  the 
  

   fused 
  mass 
  of 
  abdominal 
  ganglia, 
  but 
  they 
  are 
  represented 
  as 
  spread 
  out 
  by 
  

   dissection 
  in 
  fig. 
  8. 
  The 
  nerves 
  issuing 
  from 
  the 
  first 
  abdominal 
  ganglion 
  

   segment 
  can 
  be 
  traced 
  to 
  the 
  first 
  pair 
  of 
  modified 
  copulatory 
  abdominal 
  

   limbs 
  of 
  the 
  male. 
  In 
  this 
  condensed 
  and 
  abbreviated 
  representative 
  of 
  the 
  

   abdominal 
  nerve 
  chain 
  no 
  trace 
  of 
  connectives 
  nor 
  of 
  ihe 
  paired 
  stucture 
  of 
  

   the 
  ganglia 
  can 
  be 
  detected, 
  The 
  abdominal 
  ganglia 
  and 
  the 
  nerves 
  passing 
  

   from 
  them 
  to 
  the 
  abdomen 
  lie 
  in 
  the 
  concavity 
  of 
  the 
  narrow 
  sella 
  turcica 
  

   posterior 
  formed 
  by 
  the 
  deeply 
  infolded 
  sternal 
  apodemes 
  of 
  the 
  last 
  two 
  

   thoracic 
  segments. 
  PI. 
  4. 
  fig. 
  10 
  is 
  a 
  representation 
  of 
  the 
  ventral 
  nerve 
  

   chain 
  of 
  Lyreidus 
  tridentatus. 
  The 
  general 
  plan 
  is 
  similar 
  to 
  that 
  of 
  Ranina, 
  

   but 
  the 
  details 
  are 
  different. 
  The 
  suboesophagal 
  ganglion 
  is 
  an 
  ovoid 
  mass, 
  

   formed 
  by 
  the 
  fusion 
  of 
  the 
  ganglia 
  of 
  the 
  mandibles, 
  maxilla?, 
  and 
  maxilli- 
  

   peds. 
  As 
  I 
  could 
  only 
  count 
  five 
  nerves 
  given 
  off 
  from 
  this 
  ganglion 
  on 
  

   either 
  side, 
  I 
  conclude 
  that 
  the 
  mandibular 
  nerve 
  issues, 
  as 
  in 
  Ranina, 
  from 
  

   the 
  circum-cesophageal 
  connectives, 
  but 
  I 
  was 
  not 
  able 
  to 
  verify 
  this 
  point. 
  

   The 
  ganglion-pair 
  of 
  the 
  chelipeds 
  instead 
  of 
  being 
  approximated 
  to 
  the 
  

   oesophageal 
  as 
  in 
  Ranina, 
  is 
  placed 
  further 
  back 
  in 
  the 
  thorax 
  and 
  is 
  united 
  

   with 
  the 
  subcesophageal 
  by 
  a 
  thick 
  cord, 
  in 
  which 
  I 
  could 
  not 
  trace 
  any 
  

   separation 
  of 
  the 
  connectives 
  in 
  the 
  middle 
  line. 
  JMy 
  specimen 
  was 
  none 
  

   too 
  well 
  preserved, 
  but 
  I 
  can 
  say 
  for 
  certain 
  that 
  these 
  connectives 
  are 
  bound 
  

   together 
  in 
  the 
  same 
  connective-tissue 
  sheath. 
  The 
  ganglion-pairs 
  of 
  the 
  

   chelipeds 
  and 
  first 
  pereiopods 
  are 
  distant 
  and, 
  as 
  in 
  Ranina, 
  their 
  connectives 
  

   are 
  separated 
  by 
  a 
  distinct 
  slit-like 
  space. 
  The 
  posterior 
  thoracic 
  ganglia 
  

   are 
  more 
  closely 
  approximated 
  than 
  in 
  Ranina, 
  and 
  the 
  short 
  connectives 
  

   between 
  the 
  ganglion-pairs 
  of 
  the 
  first 
  and 
  second 
  pereiopods 
  are 
  bound 
  

  

  