﻿176 
  

  

  E. 
  RAY 
  LANKESTER. 
  

  

  opposite 
  side. 
  On 
  the 
  other 
  haiid^ 
  in 
  Scorpio 
  the 
  gill-book- 
  

   bearing 
  appendage 
  has 
  suuk 
  below 
  the 
  surface, 
  forming 
  a 
  

   recess 
  or 
  chamber 
  for 
  itself, 
  which 
  communicates 
  with 
  the 
  

   exterior 
  by 
  an 
  oval 
  or 
  circular 
  '^stigma" 
  (Fig. 
  10, 
  sty.). 
  That 
  

   this 
  in-sinking 
  has 
  taken 
  place, 
  and 
  that 
  the 
  lung-books 
  or 
  

   in-sunken 
  gill-books 
  of 
  Scorpio 
  really 
  represent 
  appendages 
  

   (that 
  is 
  to 
  say, 
  limbs 
  or 
  parapodia), 
  is 
  proved 
  by 
  their 
  develop- 
  

  

  Fig. 
  15. 
  — 
  The 
  remaining 
  three 
  pairs 
  of 
  mesosomalic 
  appendages 
  

   of 
  Scorpio 
  and 
  Limulus. 
  Letters 
  as 
  in 
  Fig. 
  14. 
  /130 
  indicates 
  

   that 
  there 
  are 
  130 
  lamellae 
  in 
  the 
  Scorpion's 
  lung-book, 
  whilst 
  / 
  150 
  

   indicates 
  that 
  150 
  similar 
  laniellaj 
  are 
  counted 
  in 
  the 
  gill 
  of 
  Limulus. 
  

   (After 
  Laukester, 
  loc. 
  cit.) 
  

  

  mental 
  history 
  (see 
  Figs. 
  17 
  aud 
  18). 
  They 
  appear 
  at 
  first 
  as 
  

   outstandiug 
  processes 
  on 
  the 
  surface 
  of 
  the 
  body. 
  

  

  The 
  exact 
  mode 
  in 
  which 
  the 
  in-sinkiug 
  of 
  superficial 
  out- 
  

   standing 
  limbs, 
  carryiug 
  gill-lamellse, 
  has 
  historically 
  taken 
  

   place 
  has 
  been 
  a 
  matter 
  of 
  much 
  speculation. 
  It 
  was 
  to 
  be 
  

   hoped 
  that 
  the 
  specimen 
  of 
  the 
  Silurian 
  scorpion 
  (Palseo- 
  

   phonus) 
  from 
  Scotland, 
  showing 
  the 
  ventral 
  surface 
  of 
  the 
  

   mesosoma 
  (1^'ig. 
  49), 
  would 
  throw 
  light 
  on 
  this 
  matter 
  ; 
  but 
  

  

  