﻿STRUCTURE 
  AND 
  CLASSIFICATION 
  OF 
  THE 
  ARACHNIDA. 
  J93 
  

  

  opens, 
  even 
  in 
  the 
  adult 
  condition, 
  by 
  a 
  minute 
  pore 
  on 
  the 
  

   coxa 
  of 
  the 
  fifth 
  leg 
  (Patten 
  and 
  Hazen 
  [13a]). 
  Previously 
  to 
  

   this, 
  Lankester's 
  pupil 
  Gulland 
  had 
  shown 
  (1885) 
  that 
  in 
  the 
  

   embryo 
  the 
  coxal 
  gland 
  is 
  a 
  comparatively 
  simple 
  tube, 
  

   which 
  opens 
  to 
  the 
  exterior 
  in 
  this 
  position, 
  and 
  by 
  its 
  other 
  

   extremity 
  into 
  a 
  ccelomic 
  space. 
  Similar 
  observations 
  were 
  

   made 
  by 
  Laurie 
  (17) 
  in 
  Lankester's 
  laboratory 
  (1890) 
  with 
  

   regard 
  to 
  the 
  early 
  coudition 
  of 
  the 
  coxal 
  gland 
  of 
  Scorpio, 
  

   and 
  by 
  Bertkau 
  (41) 
  as 
  to 
  that 
  of 
  the 
  spider 
  Atypus. 
  H. 
  M. 
  

   Bernard 
  (13b) 
  showed 
  that 
  the 
  opening 
  remains 
  in 
  the 
  adult 
  

   scorpion. 
  In 
  all 
  the 
  embryonic 
  or 
  permanent 
  opening 
  is 
  on 
  

   the 
  coxa 
  of 
  the 
  fifth 
  pair 
  of 
  prosomatic 
  limbs. 
  Thus 
  an 
  

   organ 
  newly 
  discovered 
  in 
  Scorpio 
  was 
  found 
  to 
  have 
  its 
  

   counterpart 
  in 
  Limulus. 
  

  

  The 
  name 
  " 
  coxal 
  gland 
  " 
  needs 
  to 
  be 
  carefully 
  distin- 
  

   guished 
  from 
  "crural 
  gland," 
  with 
  which 
  it 
  is 
  apt 
  to 
  be 
  

   confused. 
  The 
  crural 
  glands, 
  which 
  occur 
  in 
  many 
  terres- 
  

   trial 
  Arthropods, 
  are 
  epidermal 
  in 
  origin 
  and 
  totally 
  distinct 
  

   from 
  the 
  coxal 
  glands. 
  The 
  coxal 
  glands 
  of 
  the 
  Arachnida 
  

   are 
  structures 
  of 
  the 
  same 
  nature 
  as 
  the 
  green 
  glands 
  of 
  the 
  

   higher 
  Crustacea 
  and 
  the 
  so-called 
  "shell 
  glands" 
  of 
  the 
  

   Entomostraca. 
  The 
  latter 
  open 
  at 
  the 
  base 
  of 
  the 
  fifth 
  pair 
  

   of 
  limbs 
  of 
  the 
  Crustacean, 
  just 
  as 
  the 
  coxal 
  glands 
  open 
  on 
  

   the 
  coxal 
  joint 
  of 
  the 
  fifth 
  pair 
  of 
  limbs 
  of 
  the 
  Arachnid. 
  

   Both 
  belong 
  to 
  the 
  category 
  of 
  "coelomoducts," 
  namely, 
  

   tubular 
  or 
  fuuael-like 
  portions 
  of 
  the 
  coelom 
  opening 
  to 
  the 
  

   exterior 
  in 
  pairs 
  in 
  each 
  somite 
  (potentially), 
  and 
  usually 
  

   persisting 
  in 
  only 
  a 
  few 
  somites 
  as 
  either 
  "urocoels" 
  (renal 
  

   organs) 
  or 
  " 
  gonocoels 
  " 
  (genital 
  tubes). 
  In 
  Peripatus 
  they 
  

   occur 
  in 
  every 
  somite 
  of 
  the 
  body. 
  They 
  have 
  till 
  recently 
  

   been 
  very 
  generally 
  identified 
  with 
  the 
  nephridia 
  of 
  Chaetopod 
  

   worms, 
  but 
  there 
  is 
  good 
  reason 
  for 
  considering 
  the 
  true 
  

   nephridia 
  (typified 
  by 
  the 
  nephridia 
  of 
  the 
  earthworm) 
  as 
  a 
  

   distinct 
  class 
  of 
  organs 
  (see 
  Lankester 
  in 
  vol. 
  ii, 
  chap, 
  iii, 
  of 
  

   'A 
  Treatise 
  on 
  Zoology,' 
  1900). 
  The 
  genital 
  ducts 
  of 
  

   Arfchropoda 
  are 
  like 
  the 
  gi-een 
  glands, 
  shell 
  glands, 
  and 
  

   coxal 
  glands, 
  to 
  be 
  regarded 
  as 
  coelomoducts 
  (gonocoels). 
  

  

  