﻿174 
  

  

  E. 
  KAY 
  LANKESTER. 
  

  

  several 
  separate 
  small 
  eyes. 
  The 
  microscopic 
  structure 
  of 
  

   the 
  central 
  and 
  the 
  lateral 
  eyes 
  has 
  been 
  shown 
  by 
  Lankester 
  

   and 
  Bourne 
  (5) 
  to 
  differ; 
  but 
  the 
  lateral 
  eyes 
  of 
  Scorpio 
  were 
  

   shown 
  by 
  them 
  to 
  be 
  similar 
  in 
  structure 
  to 
  the 
  lateral 
  eyes 
  

   of 
  Limulus, 
  and 
  tlie 
  central 
  eyes 
  of 
  Scorpio 
  to 
  be 
  identical 
  in 
  

   structure 
  with 
  the 
  central 
  eyes 
  of 
  Limulus 
  (see 
  pp. 
  182, 
  183). 
  

   Following 
  the 
  prosoma 
  is 
  a 
  region 
  consisting 
  of 
  six 
  seg- 
  

   ments 
  (Figs. 
  14 
  and 
  15), 
  each 
  carrying 
  a 
  pair 
  of 
  plate-like 
  

   appendages 
  in 
  both 
  Limulus 
  and 
  Scorpio. 
  This 
  region 
  is 
  

   called 
  the 
  mesosoma. 
  The 
  tergites 
  of 
  this 
  region 
  and 
  those 
  

  

  Fig. 
  13. 
  — 
  Diagrams 
  of 
  tlie 
  metasternite 
  st, 
  with 
  genital 
  operculum 
  

   op, 
  and 
  tlie 
  first 
  lamelligerous 
  pair 
  of 
  appendages 
  ga, 
  with 
  uniting 
  

   sternal 
  element 
  st 
  of 
  Scorpio 
  (left) 
  and 
  Limulus 
  (right). 
  (From 
  

   Lankester, 
  loo. 
  cit.) 
  

  

  of 
  the 
  following 
  region, 
  the 
  metasomn, 
  arc 
  fused 
  to 
  form 
  a 
  

   second 
  or 
  posterior 
  carapace 
  in 
  Limulus, 
  whilst 
  remaining 
  

   free 
  in 
  Scorpio. 
  The 
  first 
  pair 
  of 
  foliaceous 
  appendages 
  in 
  

   each 
  animal 
  is 
  the 
  genital 
  operculum 
  ; 
  beneath 
  it 
  are 
  found 
  

   the 
  openings 
  of 
  the 
  genital 
  ducts. 
  The 
  second 
  pair 
  of 
  meso- 
  

   somatic 
  appendages 
  in 
  Scorpio 
  are 
  known 
  as 
  the 
  " 
  pecteus." 
  

   Each 
  consists 
  of 
  an 
  axis, 
  bearing 
  numerous 
  blunt 
  tooth-like 
  

   processes 
  arranged 
  in 
  a 
  series. 
  This 
  is 
  represented 
  in 
  

   Limulus 
  by 
  the 
  first 
  gill-bearing 
  appendage. 
  The 
  leaves 
  

   (some 
  150 
  in 
  number) 
  of 
  the 
  gill-book 
  (see 
  figure) 
  correspond 
  

   to 
  the 
  tooth-like 
  processes 
  of 
  the 
  pectens 
  of 
  Scorpio. 
  The 
  

  

  