﻿J4 
  

  

  ASTACUS 
  FLUVIATILIS, 
  

  

  359 
  

  

  On 
  the 
  Existence 
  of 
  an 
  Anterior 
  Rudimentary 
  

   Gill 
  in 
  Astacus 
  fUiviatilis, 
  Fabr. 
  

  

  Margery 
  Moseley. 
  

  

  WiUi 
  Plates 
  23 
  and 
  24. 
  

  

  The 
  theoretical 
  gill 
  formula 
  for 
  the 
  Decapod 
  Crustacea 
  is 
  

   four 
  on 
  each 
  side 
  of 
  each 
  somite, 
  corresponding 
  to 
  the 
  three 
  

   maxillipeds 
  and 
  the 
  five 
  legs 
  — 
  that 
  is, 
  Somites 
  VII 
  to 
  XIV, 
  

   counting 
  the 
  ophthalmic 
  somite 
  as 
  No. 
  1. 
  

  

  Professor 
  Huxley 
  distinguished 
  the 
  four 
  gill 
  plumes 
  

   according 
  to 
  their 
  position 
  on 
  the 
  somite. 
  He 
  recognised 
  one 
  

   podobranch 
  on 
  the 
  limb, 
  two 
  arthrobranchs 
  on 
  the 
  arthrodial 
  

   membrane, 
  and 
  a 
  pleurobranch 
  on 
  the 
  pleuron 
  or 
  side 
  of 
  the 
  

   somite 
  between 
  the 
  leg-joint 
  and 
  the 
  tergum. 
  

  

  The 
  complete 
  theoretical 
  gill 
  formula 
  according 
  to 
  Huxley 
  

   for 
  one 
  side 
  of 
  the 
  animal 
  would 
  be 
  — 
  

  

  Pleuro- 
  

   branchiae. 
  

  

  Total. 
  

   4 
  

   4 
  

  

  4 
  

   4 
  

  

  4 
  

   4 
  

   4 
  

   4 
  

  

  32 
  

  

  The 
  nearest 
  approach 
  to 
  this 
  is 
  found 
  in 
  certain 
  Peneeidse, 
  

  

  VOL. 
  48, 
  PART 
  3. 
  — 
  NEW 
  SEKIES. 
  26 
  

  

  