﻿A 
  STUDY 
  IX 
  CARCINOLOGY. 
  65 
  

  

  observation 
  and 
  experiment 
  of 
  such 
  complicated 
  functions 
  as 
  those 
  dealt 
  with 
  

   in 
  the 
  foregoing 
  paragraphs 
  if 
  there 
  were 
  not 
  very 
  clear 
  evidence 
  thai 
  such 
  

   an 
  anterior 
  inhalant 
  current 
  as 
  I 
  have 
  described 
  does 
  in 
  fact 
  exist. 
  One 
  

   such 
  piece 
  of 
  evidence 
  is 
  afforded 
  by 
  the 
  matted 
  feltwork 
  of 
  hairs 
  covering 
  

   the 
  ventral 
  surfaces 
  of 
  the 
  expanded 
  anterior 
  extremities 
  of 
  the 
  exopods 
  of 
  

   the 
  first 
  maxillipeds. 
  These 
  hairs 
  lie 
  flat 
  and 
  point 
  backwards 
  : 
  they 
  are 
  as 
  

   evidently 
  laid 
  back 
  by 
  a 
  current 
  of 
  water 
  passing 
  over 
  them 
  as 
  the 
  sea-grass 
  

   on 
  the 
  mud-banks 
  of 
  an 
  estuary 
  is 
  laid 
  back 
  by 
  the 
  tide 
  that 
  has 
  swept 
  over 
  

   it. 
  Again, 
  in 
  most 
  examples 
  of 
  Ranina 
  a 
  considerable 
  amount 
  of 
  sand 
  is 
  

   entangled 
  in 
  the 
  setae 
  with 
  which 
  both 
  the 
  exopods 
  and 
  endopods 
  of 
  the 
  

   second 
  maxillipeds 
  are 
  abundantly 
  furnished. 
  This 
  gives 
  evidence 
  that 
  these 
  

   appendages 
  are 
  bathed 
  by 
  a 
  current 
  of 
  water 
  not 
  wholly 
  freed 
  from 
  sand- 
  

   particles 
  by 
  the 
  filtering 
  apparatus 
  of 
  the 
  orbits 
  and 
  antennas. 
  But 
  perhaps 
  

   the 
  clearest 
  evidence 
  of 
  all 
  was 
  furnished 
  by 
  the 
  large 
  Ranina 
  sent 
  me 
  by 
  

   Prof. 
  Kishinoye. 
  In 
  this 
  specimen 
  the 
  inner 
  surfaces 
  of 
  the 
  third 
  pedun- 
  

   cular 
  segments 
  of 
  the 
  antennae, 
  the 
  ventral 
  surfaces 
  of 
  the 
  exopods 
  of 
  the 
  

   first 
  and 
  second 
  maxillipeds, 
  the 
  inner 
  surfaces 
  of 
  the 
  mastigobranchs 
  of 
  the 
  

   first 
  maxillipeds, 
  the 
  proximal 
  part 
  of 
  the 
  mastigobranchs 
  of 
  the 
  second 
  

   maxillipeds, 
  and 
  the 
  bases 
  of 
  the 
  podobranchs 
  of 
  the 
  second 
  and 
  third 
  maxilli- 
  

   peds 
  were 
  infested 
  by 
  numerous 
  small 
  pedunculate 
  cirrhipedes 
  belonging 
  

   to 
  some 
  as 
  yet 
  undetermined 
  genus 
  and 
  species 
  of 
  the 
  family 
  Lepadkke. 
  

   In 
  other 
  words, 
  these 
  intruders 
  had 
  established 
  themselves 
  alono- 
  what 
  I 
  

   have 
  described 
  as 
  the 
  course 
  of 
  the 
  incurrent 
  respiratory 
  stream, 
  but 
  none 
  

   were 
  to 
  be 
  found 
  in 
  the 
  upper 
  part 
  of 
  the 
  gill- 
  chamber, 
  nor 
  on 
  the 
  scapho- 
  

   gnathite, 
  nor 
  on 
  any 
  part 
  of 
  the 
  walls 
  of 
  the 
  exhalant 
  canals. 
  It 
  is 
  evident 
  

   that 
  their 
  larvse 
  had 
  been 
  swept 
  by 
  the 
  incurrent 
  stream 
  into 
  the 
  inhalant 
  

   chamber, 
  and 
  had 
  subsequently 
  fixed 
  themselves 
  in 
  positions 
  where 
  the 
  adults 
  

   could 
  obtain 
  a 
  constant 
  supply 
  of 
  nourishment 
  borne 
  by 
  the 
  incoming 
  current. 
  

   But, 
  where 
  the 
  currents 
  were 
  setting 
  outwards, 
  conditions 
  were 
  unfavour- 
  

   able 
  and 
  none 
  had 
  established 
  themselves. 
  

  

  From 
  what 
  precedes, 
  it 
  follows 
  that 
  Ranina, 
  no 
  less 
  than 
  Xotopus, 
  is 
  highly 
  

   adaptable 
  in 
  respect 
  of 
  its 
  respiratory 
  arrangements, 
  and 
  can 
  make 
  use 
  

   of 
  different 
  mechanisms 
  as 
  the 
  circumstances 
  of 
  the 
  moment 
  may 
  require. 
  

   When 
  half 
  buried 
  in 
  loose 
  sand 
  or 
  when 
  wandering 
  on 
  the 
  surface 
  these 
  

   animals 
  probably 
  respire 
  through 
  the 
  apertures 
  at 
  the 
  posterior 
  end 
  of 
  the 
  

   thorax. 
  When 
  deeply 
  buried 
  in 
  compact 
  sand 
  they 
  are 
  forced 
  to 
  rely 
  on 
  the 
  

   antennary 
  apparatus. 
  In 
  point 
  of 
  efficiency 
  and 
  specialisation 
  their 
  

   respiratory 
  mechanisms 
  fall 
  far 
  short 
  of 
  those 
  exhibited 
  by 
  other 
  " 
  Oxysto- 
  

   matous" 
  crabs, 
  the 
  Leucosiidaa, 
  the 
  Cahrppinse, 
  and 
  the 
  Matutimc, 
  but 
  

   adaptability 
  to 
  varying 
  conditions 
  implies 
  a 
  high 
  survival 
  value, 
  and 
  it 
  is 
  to 
  

   be 
  remarked 
  that 
  JS 
  T 
  otopus 
  and 
  Ranina 
  are 
  among 
  the 
  oldest 
  of 
  the 
  fossil 
  

   Raninidre. 
  

  

  LINN. 
  JOURN. 
  — 
  ZOOLOGY, 
  VOL. 
  XXXV. 
  5 
  

  

  