﻿A 
  STUDY 
  IN 
  CARCINOLOGY. 
  71 
  

  

  their 
  turn 
  are 
  overlapped 
  by 
  the 
  broad 
  anterior 
  margins 
  of 
  the 
  meri 
  o£ 
  the 
  

   third 
  maxillipeds. 
  The 
  left 
  antenna 
  is 
  elosed 
  nearly 
  as 
  far 
  as 
  it 
  will 
  go 
  

   against 
  the 
  antennule, 
  and 
  this 
  is 
  the 
  more 
  normal 
  position: 
  that 
  of 
  the 
  right 
  

   side 
  (the 
  spectator's 
  left) 
  has 
  been 
  pulled 
  outwards 
  to 
  show 
  the 
  passage 
  

   between 
  the 
  third 
  and 
  fourth 
  joints 
  of 
  the 
  antennary 
  peduncle 
  and 
  the 
  basal 
  

   joint 
  of 
  the 
  antennules. 
  Through 
  this 
  passage 
  water 
  can 
  pass 
  from 
  the 
  

   orbits 
  to 
  the 
  inhalant 
  chamber 
  covered 
  in 
  below 
  by 
  the 
  meri 
  of 
  the 
  third 
  

   maxillipeds. 
  The 
  arrangements 
  are 
  very 
  much 
  the 
  same 
  as 
  in 
  Ranina 
  though 
  

   somewhat 
  less 
  highly 
  specialised. 
  In 
  Raninoides 
  (figs. 
  36 
  & 
  37) 
  and 
  Lyreidus 
  

   (ligs. 
  38 
  & 
  39) 
  the 
  basal 
  joints 
  of 
  both 
  antennules 
  and 
  antenna? 
  are 
  longer 
  

   and 
  more 
  slender, 
  and 
  to 
  that 
  extent 
  more 
  primitive 
  than 
  in 
  frotosceles 
  and 
  

   Ranina. 
  In 
  the 
  antennules 
  the 
  admedian 
  surfaces 
  of 
  the 
  basal 
  joints 
  of 
  the 
  

   antennules 
  are 
  expanded 
  and 
  somewhat 
  concave, 
  so 
  that 
  when 
  opposed 
  they 
  

   form 
  a 
  conduit 
  for 
  the 
  exhalant 
  current. 
  The 
  third 
  segment 
  of 
  the 
  anten- 
  

   nary 
  peduncle 
  is 
  long; 
  a 
  good 
  deal 
  longer 
  in 
  Lyreidus 
  than 
  in 
  Raninoides. 
  

   The 
  crest 
  is 
  prominent 
  but 
  narrow, 
  and 
  extends 
  nearly 
  as 
  far 
  forward 
  as 
  the 
  

   end 
  of 
  i 
  he 
  fourth 
  segment. 
  The 
  proportions 
  differ 
  slightly 
  in 
  the 
  two 
  species, 
  

   but 
  the 
  general 
  character 
  is 
  the 
  same. 
  The 
  nature 
  and 
  distribution 
  of 
  the 
  

   hairy 
  fringes 
  are 
  clearly 
  shown 
  in 
  the 
  drawings. 
  The 
  relative 
  positions 
  of 
  

   the 
  antennules 
  and 
  antennae 
  are 
  shown 
  in 
  fig. 
  58 
  for 
  Raninoides 
  : 
  they 
  are 
  

   hardly 
  different 
  in 
  Lyreidus. 
  It 
  will 
  be 
  observed 
  that 
  the 
  "spout" 
  of 
  the 
  

   antennary 
  sternum 
  is 
  produced 
  to 
  open 
  well 
  forward 
  between 
  the 
  basal 
  joints 
  

   of 
  the 
  antennules 
  : 
  it 
  hardly 
  extends 
  as 
  far 
  forward 
  in 
  Lyreidus. 
  In 
  both 
  

   genera, 
  but 
  to 
  a 
  greater 
  extent 
  in 
  Lyreidus 
  than 
  in 
  Raninoides, 
  the 
  third 
  

   peduncular 
  segment 
  of 
  the 
  antenna 
  is 
  overlapped 
  by 
  the 
  tip 
  of 
  the 
  elongated 
  

   merus 
  of 
  the 
  third 
  maxillipeds, 
  and 
  the 
  portion 
  not 
  overlapped 
  is 
  covered 
  by 
  

   a 
  tuft 
  of 
  long 
  hairs 
  projecting 
  forward 
  from 
  the 
  tip 
  of 
  the 
  merus. 
  The 
  inner 
  

   laces 
  of 
  the 
  third 
  peduncular 
  segments 
  of 
  the 
  antenna? 
  and 
  their 
  crests 
  are 
  so 
  

   shaped 
  that 
  when 
  bent 
  inwards 
  they 
  fit 
  very 
  exactly 
  to 
  the 
  outer 
  surfaces 
  of 
  

   the 
  basal 
  joints 
  of 
  the 
  antennules, 
  and 
  when 
  in 
  this 
  position 
  completely 
  bar 
  

   the 
  passage 
  of 
  water 
  from 
  the 
  orbits 
  to 
  the 
  inhalant 
  chamber 
  above 
  the 
  third 
  

   maxillipeds. 
  But 
  when 
  the 
  antenna? 
  diverge 
  slightly 
  outwards 
  a 
  clear 
  

   passage 
  is 
  left 
  between 
  the 
  antennules 
  and 
  the 
  antennae, 
  and 
  the 
  intrusion 
  of 
  

   sand 
  is 
  guarded 
  against 
  by 
  the 
  overlapping 
  bristles 
  of 
  both. 
  Through 
  this 
  

   passage, 
  I 
  think, 
  the 
  inhalant 
  current 
  must 
  pass 
  when 
  the 
  scaphognathite 
  is 
  

   working 
  normally, 
  and 
  through 
  it 
  the 
  excurrent 
  stream 
  must 
  flow 
  when 
  the 
  

   action 
  of 
  the 
  scaphognathite 
  is 
  reversed. 
  But 
  the 
  subject 
  is 
  very 
  obscure, 
  

   and 
  I 
  am 
  by 
  no 
  means 
  content 
  with 
  this 
  explanation. 
  I 
  give 
  it 
  for 
  what 
  it 
  is 
  

   worth 
  in 
  the 
  hope 
  that 
  some 
  favourably 
  placed 
  naturalist 
  may 
  read 
  it, 
  find 
  

   fault 
  with 
  it, 
  and 
  straightway 
  proceed 
  to 
  make 
  observations 
  and 
  experiments 
  

   on 
  the 
  living 
  animals. 
  The 
  results 
  cannot 
  fail 
  to 
  be 
  of 
  interest. 
  I 
  feel 
  

   certain 
  only 
  of 
  this, 
  that 
  there 
  is 
  an 
  inhalant 
  current 
  between 
  the 
  third 
  and 
  

  

  