﻿STKUCTUKE 
  AND 
  CLASSiriCATlOK 
  OF 
  THE 
  AEACHNIUA. 
  265 
  

  

  (Ixodes) 
  are 
  not 
  only 
  injurious 
  as 
  blood-suckers, 
  but 
  are 
  now 
  

   credited 
  with 
  carrying 
  the 
  genus 
  of 
  Texan 
  cattle 
  fever, 
  just 
  

   as 
  mosquitoes 
  carry 
  those 
  of 
  malaria. 
  The 
  itch 
  insect 
  

   (Sarcoptes 
  scabiei) 
  is 
  a 
  well-known 
  human 
  parasite, 
  so 
  

   minute 
  that 
  it 
  was 
  not 
  discovered 
  until 
  the 
  end 
  of 
  the 
  eigh- 
  

   teenth 
  century, 
  and 
  " 
  the 
  itch" 
  was 
  treated 
  medicinally 
  as 
  a 
  

   rash. 
  The 
  female 
  burrows 
  in 
  the 
  epidermis 
  much 
  as 
  the 
  female 
  

   trapdoor 
  spider 
  burrows 
  in 
  turf, 
  in 
  order 
  to 
  make 
  a 
  nest 
  in 
  

   Avhich 
  to 
  rear 
  her 
  young. 
  The 
  male 
  does 
  not 
  burrow, 
  but 
  

   wanders 
  freely 
  on 
  the 
  surface 
  of 
  the 
  skin. 
  Demodex 
  folli- 
  

   culorumis 
  also 
  a 
  common 
  parasite 
  of 
  the 
  sebaceous 
  glands 
  of 
  

   the 
  skin 
  of 
  the 
  face 
  in 
  man, 
  and 
  is 
  frequent 
  in 
  the 
  skin 
  of 
  the 
  

   dog. 
  Many 
  Acari 
  are 
  parasitic 
  on 
  marine 
  and 
  fresh-water 
  

   molluscs, 
  and 
  others 
  are 
  found 
  on 
  the 
  feathers 
  of 
  birds 
  and 
  the 
  

   hairs 
  of 
  mammals. 
  Others 
  have 
  a 
  special 
  faculty 
  of 
  consuming- 
  

   dry, 
  powdery 
  vegetable 
  and 
  animal 
  refuse, 
  and 
  are 
  liable 
  to 
  mul- 
  

   tiply 
  in 
  manufactured 
  products 
  of 
  this 
  nature, 
  such 
  as 
  mouldy 
  

   cheese. 
  A 
  species 
  of 
  Acarus 
  is 
  recorded 
  as 
  infesting 
  a 
  store 
  

   of 
  powdered 
  strychnine, 
  and 
  feeding 
  on 
  that 
  drug, 
  so 
  poison- 
  

   ous 
  to 
  larger 
  organisms. 
  (Reference 
  to 
  literature, 
  40.) 
  

  

  AUTHOEITIES 
  CITED 
  BY 
  NUMBERS 
  IN 
  THE 
  TEXT. 
  

  

  1. 
  Steaus-Durkheim 
  (as 
  reported 
  by 
  MM. 
  Riester 
  and 
  Sanson 
  in 
  an 
  

  

  appendix 
  to 
  the 
  sixtli 
  volume 
  of 
  tlie 
  French 
  translation 
  of 
  Meckel's 
  

   'Anatomy,' 
  1S29). 
  

  

  2. 
  Lankester. 
  — 
  "Limulus 
  an 
  Arachnid," 
  'Quart. 
  Journ. 
  Micr. 
  Sci.,' 
  vol. 
  

  

  xxi, 
  N.S., 
  1881. 
  

  

  3. 
  Lankester. 
  — 
  "On 
  the 
  Skeletotrophic 
  Tissues 
  of 
  Limulus, 
  Scorpio, 
  and 
  

  

  Mygale," 
  'Quart. 
  Journ. 
  Micr. 
  Sci.,' 
  vol. 
  xxiv, 
  N.S., 
  ISS-l. 
  

  

  4. 
  Lankesteu. 
  — 
  'Trans. 
  Zool. 
  Soc.,' 
  vol. 
  xi, 
  1883. 
  

  

  5. 
  Lankestek 
  and 
  Bourne. 
  — 
  "Eyes 
  of 
  Limulus 
  and 
  Scorpio," 
  'Quart. 
  

  

  Journ. 
  Micr. 
  Sci.,' 
  vol. 
  xxiii, 
  N.S., 
  Jan., 
  1883. 
  

  

  6. 
  Milne-Edwards, 
  A. 
  — 
  "Recherches 
  sur 
  I'anatomie 
  des 
  Limules," 
  'Ann. 
  

  

  Sci. 
  Nat.,' 
  5th 
  series, 
  " 
  Zoologie," 
  vol. 
  xvii, 
  1873. 
  

  

  7. 
  Owen, 
  Richard. 
  — 
  "Anatomy 
  of 
  the 
  King-crab," 
  'Trans. 
  Linn. 
  Soc. 
  

  

  Lond.,' 
  vol. 
  xxviii, 
  1872. 
  

  

  