﻿DISTRIBUTION 
  OF 
  FISHES 
  — 
  JORDAN 
  385 
  

  

  free 
  waters 
  play 
  in 
  ceaseless 
  torrents, 
  and 
  there 
  they 
  have 
  wrested 
  from 
  stub- 
  

   born 
  Nature 
  a 
  meager 
  living. 
  Although 
  diminished 
  in 
  size 
  by 
  their 
  continual 
  

   struggle 
  with 
  the 
  elements, 
  they 
  have 
  developed 
  an 
  activity 
  and 
  hardihood, 
  a 
  

   vigor 
  of 
  life, 
  and 
  glow 
  of 
  high 
  color 
  almost 
  unknown 
  among 
  the 
  easier 
  livers 
  of 
  

   tlie 
  lower 
  lands. 
  

  

  It 
  is 
  noteworthy 
  that 
  among 
  the 
  European 
  genera 
  of 
  PercidcB 
  one 
  

   of 
  them, 
  Aspro 
  (properly 
  Asper), 
  has 
  assumed 
  a 
  simihir 
  habitat 
  and 
  

   adapted 
  — 
  apparently 
  as 
  a 
  result 
  of 
  its 
  surroundings 
  — 
  characters 
  

   similar 
  to 
  those 
  of 
  Etheostoma 
  and 
  its 
  allies. 
  It 
  is 
  not 
  likely 
  that 
  

   Asper 
  is 
  an 
  ancestor 
  of 
  Etheostoma 
  or 
  Percina^ 
  still 
  less 
  likely 
  that 
  

   Asper 
  is 
  descended 
  from 
  any 
  American 
  genus. 
  The 
  similar 
  develop- 
  

   ment 
  of 
  the 
  two 
  is 
  rather 
  a 
  case 
  of 
  analogous 
  variation, 
  the 
  influence 
  

   of 
  similar 
  conditions 
  in 
  different 
  places 
  on 
  different 
  organisms. 
  

  

  It 
  is 
  remarkable 
  also 
  that 
  in 
  mountain 
  regions, 
  in 
  which 
  no 
  Per- 
  

   cidce 
  are 
  found, 
  fishes 
  very 
  similar 
  to 
  the 
  darters 
  in 
  appearance 
  and 
  

   habits 
  though 
  totally 
  different 
  in 
  structure 
  have 
  by 
  analogous 
  agencies 
  

   been 
  developed. 
  Loaches, 
  catfishes, 
  gobies, 
  characins, 
  sculpins 
  in 
  

   different 
  parts 
  of 
  the 
  world 
  inhabit 
  swift 
  mountain 
  streams 
  and 
  in 
  a 
  

   similar 
  way 
  become 
  dwarfed 
  and 
  concentrated, 
  taking 
  the 
  place 
  in 
  

   their 
  respective 
  habitats 
  which 
  the 
  darters 
  occupy 
  in 
  the 
  waters 
  of 
  

   the 
  Mississippi 
  Valley. 
  

  

  By 
  the 
  same 
  process 
  of 
  " 
  analogous 
  variation 
  " 
  the 
  Cichlidm 
  of 
  

   South 
  America 
  parallel 
  the 
  sunfishes 
  of 
  the 
  United 
  States, 
  although 
  

   in 
  structure 
  and 
  in 
  origin 
  the 
  two 
  groups 
  are 
  diverse. 
  

  

  The 
  single 
  species 
  each 
  of 
  drwni 
  {Aplodinotus 
  grunnwns 
  Rafi- 
  

   nesque), 
  surf 
  fsh 
  {Hysterocarpus 
  traski 
  Gibbons), 
  and 
  cod 
  {Lota 
  lota 
  

   Linnaeus) 
  found 
  in 
  our 
  fresh 
  waters 
  are 
  evidently 
  immigrants 
  from 
  

   the 
  sea, 
  although 
  not 
  of 
  very 
  recent 
  origin. 
  The 
  several 
  fresh-water 
  

   species 
  of 
  Sculpin 
  have 
  apparently 
  come 
  from 
  two 
  separate 
  marine 
  

   stocks 
  — 
  the 
  one 
  (Cottus) 
  comparatively 
  ancient 
  and 
  probably 
  origi- 
  

   nating 
  in 
  the 
  Pacific, 
  the 
  other 
  Triglopsis 
  more 
  modern 
  and 
  descended 
  

   from 
  an 
  Atlantic 
  species 
  {Oncocottus 
  quadricornis 
  L.). 
  The 
  former 
  

   type 
  is 
  now 
  diffused 
  in 
  all 
  cold 
  waters 
  of 
  North 
  America, 
  Europe, 
  and 
  

   northern 
  Asia. 
  The 
  latter 
  belongs 
  only 
  to 
  the 
  depths 
  of 
  our 
  Great 
  

   Lakes. 
  

  

  The 
  -flounders 
  and 
  soles 
  when 
  found 
  in 
  fresh 
  waters 
  are 
  merely 
  

   temporary 
  sojourners 
  from 
  the 
  sea. 
  

  

  