﻿STRUCTURE 
  AND 
  CLASSIFICATION 
  OF 
  THE 
  AIUCHNIDA. 
  209 
  

  

  the 
  spiders, 
  the 
  Pedipalps, 
  and 
  other 
  large 
  Arachnids 
  have 
  

   not 
  been 
  derived 
  from 
  the 
  scorpions 
  directl}^ 
  but 
  have 
  

   independently 
  developed 
  from 
  aquatic 
  ancestors, 
  and 
  from 
  

   one 
  of 
  those 
  independent 
  groups 
  — 
  probably 
  through 
  the 
  

   harvestmen 
  from 
  the 
  spiders 
  — 
  the 
  Acari 
  have 
  finally 
  re- 
  

   sulted. 
  

  

  Leaving 
  that 
  question 
  for 
  consideration 
  in 
  connection 
  with 
  

   the 
  systematic 
  statement 
  of 
  the 
  characters 
  of 
  the 
  various 
  

   groups 
  of 
  Arachnida 
  which 
  follows 
  below, 
  it 
  is 
  well 
  now 
  to 
  

   consider 
  the 
  following 
  question, 
  viz. 
  seeing 
  that 
  Limulus 
  and 
  

   Scorpio 
  are 
  such 
  highly 
  developed 
  und 
  specialised 
  forms, 
  and 
  

   that 
  they 
  seem 
  to 
  constitute, 
  as 
  it 
  were, 
  the 
  first 
  and 
  second 
  

   steps 
  in 
  the 
  series 
  of 
  recognised 
  Arachnida, 
  what 
  do 
  we 
  

   know, 
  or 
  what 
  are 
  we 
  led 
  to 
  suppose 
  with 
  regard 
  to 
  the 
  more 
  

   primitive 
  Arachnida 
  from 
  which 
  the 
  Eurypterines 
  and 
  Limu- 
  

   lus 
  and 
  Scorpio 
  have 
  sprung 
  ? 
  Do 
  we 
  know, 
  in 
  the 
  recent 
  or 
  

   fossil 
  condition, 
  any 
  such 
  primitive 
  Arachnids 
  ? 
  Such 
  a 
  

   question 
  is 
  not 
  only 
  legitimate, 
  but 
  prompted 
  by 
  the 
  analogy 
  

   of 
  at 
  least 
  one 
  other 
  great 
  class 
  of 
  Arthropods. 
  The 
  great 
  

   Arthropod 
  class, 
  the 
  Crustacea, 
  presents 
  to 
  the 
  zoologist 
  at 
  

   the 
  present 
  day 
  an 
  immense 
  range 
  of 
  forms, 
  comprising 
  the 
  

   primitive 
  Phjllopods, 
  the 
  minute 
  Copepods, 
  the 
  parasitic 
  

   Cirrhipedes 
  and 
  the 
  powerful 
  crabs 
  and 
  lobsters, 
  and 
  the 
  

   highly 
  elaborated 
  sand-hoppers 
  and 
  slaters. 
  It 
  has 
  been 
  

   insisted, 
  by 
  those 
  who 
  accepted 
  Lankester's 
  original 
  doctrine 
  

   of 
  the 
  dii'ect 
  or 
  genetic 
  affinity 
  of 
  tlie 
  Chsetopoda 
  and 
  Arthro- 
  

   poda, 
  that 
  Apus 
  and 
  Branchipus 
  really 
  come 
  very 
  near 
  to 
  the 
  

   ancestral 
  forms 
  which 
  connected 
  those 
  two 
  great 
  branches 
  of 
  

   Appendiculate 
  (Parapodiate) 
  animals. 
  On 
  the 
  other 
  band, 
  

   the 
  land 
  crabs 
  are 
  at 
  an 
  immense 
  distance 
  from 
  these 
  simple 
  

   forms. 
  The 
  record 
  of 
  the 
  Crustacean 
  family 
  tree 
  is, 
  in 
  fact, 
  

   a 
  fairly 
  complete 
  one 
  — 
  the 
  lower 
  primitive 
  members 
  of 
  the 
  

   group 
  are 
  still 
  represented 
  by 
  living 
  forms 
  in 
  great 
  abundance. 
  

   In 
  the 
  case 
  of 
  the 
  Arachnida, 
  if 
  we 
  have 
  to 
  start 
  their 
  genea- 
  

   logical 
  history 
  with 
  Limulus 
  and 
  Scorpio, 
  we 
  are 
  much 
  in 
  the 
  

   same 
  position 
  as 
  we 
  should 
  be 
  in 
  dealing 
  with 
  the 
  Crustacea 
  

   were 
  the 
  whole 
  of 
  the 
  Entoniostraca 
  and 
  the 
  whole 
  of 
  the 
  

  

  