﻿178 
  

  

  E. 
  RAY 
  LANKESTER. 
  

  

  ing 
  organ 
  or 
  lung^ 
  but 
  there 
  is 
  no 
  other 
  case 
  known 
  of 
  the 
  

   conversion 
  of 
  gill 
  processes 
  themselves 
  into 
  air-breathing 
  

   plates. 
  

  

  The 
  identification 
  of 
  the 
  lung-boohs 
  of 
  Scorpio 
  with 
  the 
  

   gill-books 
  of 
  Limulus 
  is 
  practically 
  settled 
  by 
  the 
  existence 
  

  

  Fig. 
  17. 
  

  

  SffC 
  

  

  Fig. 
  18. 
  

  

  VIIPrG 
  

  

  Fig. 
  17. 
  — 
  Embryo 
  of 
  Scorpion, 
  ventral 
  view 
  showing 
  somites 
  and 
  

   appendages, 
  fc/c, 
  frontal 
  groove 
  ; 
  sa, 
  rudiment 
  of 
  lateral 
  eyes 
  ; 
  obi, 
  

   camerostome 
  (upper 
  lip); 
  so, 
  sense-organ 
  of 
  Patten; 
  '^vGapb^, 
  

   rudiment 
  of 
  the 
  appendage 
  of 
  the 
  prsegenital 
  somite 
  which 
  dis- 
  

   appears 
  ; 
  abp', 
  rudiment 
  of 
  tlie 
  right 
  half 
  of 
  the 
  genital 
  operculum; 
  

   abj?, 
  rudiment 
  of 
  liie 
  right 
  pecten 
  ; 
  abp* 
  to 
  abp^, 
  rudiments 
  of 
  the 
  

   four 
  appendages 
  which 
  carry 
  the 
  pulmonary 
  lamellae 
  ; 
  I 
  to 
  VI, 
  

   rudiments 
  of 
  the 
  six 
  limbs 
  of 
  the 
  piosoma 
  ; 
  VIIPrG, 
  the 
  evanescent 
  

   prsegeiiital 
  somite; 
  VIII, 
  the 
  first 
  mesosomatic 
  somite 
  or 
  genital 
  

   somite 
  ; 
  IX, 
  the 
  second 
  mesosomatic 
  somite 
  or 
  pectiniferous 
  somite 
  ; 
  

   X 
  to 
  XIII, 
  the 
  four 
  i)ulmoniferous 
  somites; 
  XIV, 
  the 
  first 
  meta- 
  

   somatic 
  somite. 
  (After 
  Brauer, 
  ' 
  Zeitsch. 
  wiss. 
  Zool.,' 
  vol. 
  lix, 
  

   1895.) 
  

  

  Fig. 
  18. 
  — 
  Portion 
  of 
  a 
  similar 
  embryo 
  at 
  a 
  later 
  stage 
  of 
  growth. 
  

   The 
  prsegenital 
  somite, 
  VIIPrG, 
  is 
  still 
  present, 
  but 
  has 
  lost 
  its 
  

   rudimentary 
  appendages; 
  go, 
  the 
  genital 
  operculum, 
  left 
  half; 
  Km, 
  

   the 
  left 
  pecten 
  ; 
  abp'^ 
  to 
  abp'', 
  the 
  rudimentary 
  appendages 
  of 
  the 
  

   lung-sacs. 
  (After 
  Brauer, 
  loc. 
  cit.) 
  

  

  of 
  the 
  pectens 
  in 
  Scorpio 
  (Fig. 
  14, 
  VIII) 
  on 
  the 
  second 
  meso- 
  

   somatic 
  somite. 
  There 
  is 
  no 
  doubt 
  that 
  these 
  are 
  parapodial 
  

   or 
  limb 
  appendages, 
  carrying 
  numerous 
  imbricated 
  secondary 
  

   processes, 
  and 
  therefore 
  comparable 
  in 
  essential 
  structure 
  to 
  

   the 
  leaf 
  -bearing 
  plates 
  of 
  the 
  second 
  mesosomatic 
  somite 
  of 
  

  

  