﻿194 
  E. 
  BAY 
  LANKESTER. 
  

  

  The 
  coxa! 
  glands 
  do 
  not 
  establish 
  any 
  special 
  connection 
  

   between 
  LimuUis 
  and 
  Scorpio, 
  since 
  they 
  also 
  occur 
  in 
  the 
  

   same 
  somite 
  in 
  the 
  lower 
  Crustacea, 
  but 
  it 
  is 
  to 
  be 
  noted 
  that 
  

   the 
  coxal 
  glands 
  of 
  Limulus 
  are 
  in 
  minute 
  structure 
  and 
  

   probably 
  in 
  function 
  more 
  like 
  those 
  of 
  Arachnids 
  than 
  those 
  

   of 
  Crustacea. 
  

  

  4. 
  The 
  Entosternites 
  and 
  their 
  Minute 
  Structure. 
  

   — 
  Straus-Durkheim 
  (1) 
  was 
  the 
  first 
  to 
  insist 
  on 
  the 
  afhnity 
  

   between 
  Limulus 
  and 
  the 
  Arachnids, 
  indicated 
  by 
  the 
  

   presence 
  of 
  a 
  free 
  suspended 
  entosternum 
  or 
  plastron 
  or 
  

   entosternite 
  in 
  both. 
  We 
  have 
  figured 
  here 
  (Figs. 
  1 
  — 
  6) 
  the 
  

   entosternites 
  of 
  Limulus, 
  Scorpio, 
  and 
  My 
  gale. 
  Lankester 
  

   some 
  years 
  ago 
  made 
  a 
  special 
  study 
  of 
  the 
  histology 
  (3) 
  of 
  

   these 
  entosternites 
  for 
  the 
  purpose 
  of 
  comparison, 
  and 
  also 
  

   ascertained 
  the 
  relations 
  of 
  the 
  very 
  numerous 
  muscles 
  which 
  

   are 
  inserted 
  into 
  them 
  (4). 
  The 
  entosternites 
  are 
  cartila- 
  

   ginous 
  in 
  texture, 
  but 
  they 
  have 
  neither 
  the 
  chemical 
  

   character 
  nor 
  the 
  microscopic 
  structure 
  of 
  the 
  hyaline 
  

   cai'tilage 
  of 
  Vertebrates. 
  They 
  yield 
  chitin 
  in 
  place 
  of 
  

   chondinn 
  or 
  gelatine 
  — 
  as 
  does 
  also 
  the 
  cartilage 
  of 
  the 
  

   Cephalopod's 
  endoskeleton. 
  In 
  microscopic 
  structure 
  they 
  

   all 
  present 
  the 
  closest 
  agreement 
  with 
  one 
  another. 
  We 
  find 
  

   a 
  firm, 
  homogeneous, 
  or 
  sparsely 
  fibrillated 
  matrix 
  in 
  which 
  

   are 
  embedded 
  nucleated 
  cells 
  (corpuscles 
  of 
  protoplasm) 
  

   arranged 
  in 
  rows 
  of 
  three, 
  six, 
  or 
  eight 
  parallel 
  with 
  the 
  

   adjacent 
  lines 
  of 
  fibrillation. 
  

  

  A 
  miuute 
  entosternite 
  having 
  the 
  above-described 
  struc- 
  

   ture 
  is 
  found 
  in 
  the 
  Crustacean 
  Apus 
  between 
  the 
  bases 
  of 
  

   the 
  mandibles, 
  and 
  also 
  in 
  the 
  Decapoda 
  in 
  a 
  similar 
  position, 
  

   but 
  in 
  no 
  Crustacean 
  does 
  it 
  attain 
  to 
  any 
  size 
  or 
  importance. 
  

   On 
  the 
  other 
  hand, 
  the 
  entosternite 
  of 
  the 
  Arachnida 
  is 
  a 
  

   very 
  large 
  and 
  important 
  feature 
  in 
  the 
  structure 
  of 
  the 
  

   prosoma, 
  and 
  must 
  play 
  an 
  important 
  part 
  in 
  the 
  economy 
  of 
  

   these 
  organisms. 
  In 
  Limulus 
  (Figs. 
  1 
  and 
  2) 
  it 
  has 
  as 
  many 
  

   as 
  twenty-five 
  pairs 
  of 
  muscles 
  attached 
  to 
  it, 
  coming 
  to 
  it 
  

   from 
  the 
  bases 
  of 
  the 
  surrounding 
  limbs 
  and 
  from 
  the 
  dorsal 
  

   carapace 
  and 
  from 
  the 
  pharynx. 
  It 
  consists 
  of 
  an 
  oblong 
  

  

  