﻿DISTRIBUTION 
  OF 
  FISHES 
  JORDAN 
  365 
  

  

  In 
  other 
  cases 
  many 
  large 
  rivers, 
  draining 
  very 
  different 
  districts 
  

   and 
  perhaps 
  flowing 
  into 
  different 
  oceans, 
  have 
  their 
  source 
  close 
  

   together 
  in 
  the 
  same 
  mountain 
  regions. 
  From 
  one 
  source 
  to 
  another 
  

   we 
  may 
  have 
  a 
  marshy 
  tra; 
  t, 
  transversable 
  at 
  high 
  water 
  by 
  the 
  few 
  

   species 
  which 
  ascend 
  thus 
  far. 
  

  

  The 
  following 
  examples 
  show 
  how 
  transfer 
  of 
  species 
  may 
  be 
  ac- 
  

   complished, 
  and 
  that 
  we 
  need 
  not 
  be 
  left 
  to 
  draw 
  on 
  the 
  imagination 
  

   to 
  invent 
  possible 
  means 
  of 
  transit. 
  

  

  There 
  are 
  few 
  watersheds 
  in 
  the 
  world 
  better 
  defined 
  than 
  the 
  

   moimtain 
  range 
  (Dovrefjeld) 
  which 
  forms 
  the 
  "backbone" 
  of 
  

   Norway. 
  I 
  lately 
  climbed 
  a 
  peak 
  in 
  this 
  range, 
  the 
  Suletind. 
  From 
  

   its 
  summit 
  I 
  could 
  look 
  down 
  into 
  the 
  valleys 
  of 
  the 
  Lara 
  and 
  the 
  

   Bagna, 
  flowing 
  in 
  opposite 
  directions 
  to 
  opposite 
  sides 
  of 
  the 
  penin- 
  

   sula. 
  To 
  the 
  north 
  of 
  the 
  Suletind 
  is 
  a 
  large 
  double 
  lake 
  called 
  the 
  

   Sletningenvand. 
  The 
  maps 
  show 
  this 
  lake 
  to 
  be 
  one 
  of 
  the 
  chief 
  

   sources 
  of 
  the 
  westward-flowing 
  river 
  Lara. 
  This 
  lake 
  is 
  in 
  August 
  

   swollen 
  by 
  the 
  melting 
  of 
  the 
  snows, 
  and 
  at 
  the 
  time 
  of 
  my 
  visit 
  it 
  

   seemed 
  to 
  be 
  the 
  source 
  of 
  both 
  these 
  rivers. 
  From 
  its 
  southeastern 
  

   side 
  flowed 
  a 
  large 
  brook 
  into 
  the 
  valley 
  of 
  the 
  Bagna, 
  and 
  from 
  its 
  

   southwestern 
  corner, 
  equally 
  distinctly, 
  came 
  the 
  waters 
  which 
  fed 
  

   the 
  Lara. 
  This 
  lake, 
  liko 
  similar 
  mountain 
  ponds 
  in 
  ail 
  northern 
  

   countries, 
  abounds 
  in 
  trout; 
  and 
  these 
  trout 
  certainly 
  have 
  for 
  part 
  

   of 
  the 
  year 
  an 
  uninterrujjted 
  line 
  of 
  water 
  communication 
  from 
  the 
  

   Sognefjord 
  on 
  the 
  west 
  of 
  Norway 
  to 
  the 
  Christianiaf 
  jord 
  on 
  the 
  

   southeast 
  — 
  from 
  the 
  North 
  Sea 
  to 
  the 
  Baltic. 
  Part 
  of 
  the 
  year 
  the 
  

   lake 
  has 
  probably 
  but 
  a 
  single 
  outlet, 
  through 
  the 
  Lara. 
  A 
  higher 
  

   temperature 
  would 
  entirely 
  cut 
  off 
  the 
  flow 
  into 
  the 
  Bagna, 
  and 
  a 
  

   still 
  higher 
  one 
  might 
  dry 
  up 
  the 
  lake 
  altogether. 
  This 
  Sletningen- 
  

   A^and, 
  with 
  its 
  two 
  outlets 
  on 
  the 
  summit 
  of 
  a 
  sharp 
  watershed, 
  may 
  

   serve 
  to 
  show 
  us 
  how 
  other 
  lakes, 
  permanent 
  or 
  temporary, 
  may 
  

   elsewhere 
  have 
  acted 
  as 
  agencies 
  for 
  the 
  transfer 
  of 
  fishes. 
  We 
  can 
  

   also 
  see 
  how 
  it 
  might 
  be 
  that 
  certain 
  mountain 
  fishes 
  should 
  be 
  so 
  

   transferred 
  while 
  the 
  fishes 
  of 
  the 
  upland 
  waters 
  may 
  be 
  left 
  behind. 
  

   In 
  some 
  such 
  way 
  as 
  this 
  we 
  may 
  imagine 
  that 
  various 
  species 
  of 
  

   fishes 
  have 
  attained 
  their 
  present 
  wide 
  range 
  in 
  the 
  Rocky 
  Mountain 
  

   region; 
  and 
  in 
  similar 
  manner 
  perhaps 
  the 
  eastern 
  brook 
  trout 
  

   {Salvel'inus 
  fontlnalis 
  ]\Iitchill) 
  and 
  some 
  other 
  mountain 
  species 
  

   {II 
  rjdro 
  phlox 
  rubricroceus 
  Cope, 
  Rhinichthys^ 
  atronasus 
  Mitchill) 
  

   may 
  have 
  been 
  carried 
  across 
  the 
  Alleghenics. 
  

  

  It 
  is 
  well 
  Imown 
  that 
  a 
  marshy 
  upland 
  in 
  Brazil 
  separates 
  the 
  

   valley 
  of 
  La 
  Plata 
  from 
  that 
  of 
  the 
  Amazon, 
  and 
  its 
  channels 
  permit 
  

   the 
  free 
  movement 
  of 
  fishes 
  from 
  the 
  Paraguay 
  River 
  to 
  the 
  Tapajos. 
  

   In 
  the 
  World 
  War 
  an 
  effort 
  was 
  made 
  to 
  transfer 
  armament 
  by 
  this 
  

   means 
  from 
  the 
  Amazon 
  to 
  Germans 
  in 
  southern 
  Brazil. 
  It 
  is 
  well 
  

  

  