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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  The 
  dispersion 
  of 
  animals 
  may 
  be 
  described 
  as 
  a 
  matter 
  of 
  space 
  

   and 
  time, 
  the 
  movement 
  bein<>^ 
  continuous 
  but 
  modified 
  by 
  barriers 
  

   and 
  other 
  conditions 
  of 
  environment. 
  The 
  tendency 
  of 
  recent 
  studies 
  

   in 
  zoogeography 
  has 
  been 
  to 
  consider 
  the 
  facts 
  of 
  present 
  distribution 
  

   as 
  the 
  result 
  of 
  conditions 
  in 
  the 
  past, 
  thus 
  correlating 
  our 
  present 
  

   knowledge 
  with 
  the 
  past 
  relations 
  of 
  land 
  and 
  water 
  as 
  shown 
  

   through 
  paleontology. 
  Dr. 
  A. 
  E. 
  Ortmann 
  well 
  observes 
  that 
  " 
  Any 
  

   division 
  of 
  the 
  earth's 
  surface 
  into 
  zoogeographical 
  regions 
  which 
  

   starts 
  exclusively 
  from 
  the 
  present 
  distribution 
  of 
  animals 
  without 
  

   considering 
  its 
  origin 
  must 
  always 
  be 
  unsatisfactory." 
  We 
  must 
  

   therefore 
  consider 
  the 
  coast 
  lines 
  and 
  barriers 
  of 
  Tertiary 
  and 
  earlier 
  

   times 
  as 
  well 
  as 
  those 
  of 
  to-day 
  to 
  understand 
  the 
  present 
  distribution 
  

   of 
  fishes. 
  

  

  The 
  general 
  laws 
  governing 
  the 
  distribution 
  of 
  all 
  animals 
  are 
  

   reducible 
  to 
  three 
  very 
  simple 
  pro}>ositions. 
  

  

  Each 
  species 
  of 
  animal 
  is 
  found 
  in 
  every 
  part 
  of 
  the 
  earth 
  having 
  

   conditions 
  suitable 
  for 
  its 
  maintenance, 
  unless 
  — 
  

  

  (a) 
  Its 
  individuals 
  have 
  been 
  unable 
  to 
  reach 
  this 
  region 
  through 
  

   barriers 
  of 
  some 
  sort 
  ; 
  or, 
  

  

  (5) 
  Having 
  reached 
  it, 
  the 
  species 
  is 
  unable 
  to 
  maintain 
  itself, 
  

   through 
  lack 
  of 
  capacity 
  for 
  adaptation, 
  through 
  severity 
  of 
  com- 
  

   petition 
  with 
  other 
  forms, 
  or 
  through 
  destructive 
  conditions 
  of 
  

   environment 
  ; 
  or 
  else, 
  

  

  ((?) 
  Having 
  entered 
  and 
  maintained 
  itself, 
  it 
  has 
  become 
  so 
  altered 
  

   in 
  the 
  process 
  of 
  adaptation 
  by 
  selection 
  as 
  to 
  become 
  a 
  species 
  distinct 
  

   from 
  the 
  original 
  type. 
  

  

  The 
  absence 
  from 
  the 
  Japanese 
  fauna 
  of 
  most 
  European 
  or 
  Amer- 
  

   ican 
  species 
  comes 
  under 
  the 
  first 
  head. 
  The 
  pike 
  has 
  never 
  reached 
  

   the 
  Japanese 
  lakes, 
  though 
  the 
  shade 
  of 
  the 
  lotus 
  leaf 
  in 
  many 
  clear 
  

   ponds 
  would 
  suit 
  its 
  habits 
  exactly. 
  The 
  grunt 
  {Haemulon) 
  and 
  

   porgies 
  {Calamus) 
  of 
  our 
  West 
  Indian 
  Avaters 
  have 
  failed 
  to 
  cross 
  

   the 
  ocean 
  and 
  therefore 
  have 
  no 
  descendants 
  in 
  Europe 
  or 
  Asia. 
  

  

  Of 
  species 
  under 
  (6), 
  those 
  who 
  have 
  crossed 
  the 
  seas 
  and 
  not 
  

   found 
  lodgment, 
  we 
  have, 
  in 
  the 
  nature 
  of 
  things, 
  no 
  record. 
  Of 
  

   the 
  existence 
  of 
  multitudes 
  of 
  estrays 
  we 
  have 
  abundant 
  evidence. 
  

   In 
  the 
  Gulf 
  Stream 
  off 
  Cape 
  Cod 
  are 
  taken 
  every 
  year 
  many 
  young 
  

   fishes 
  belonging 
  to 
  species 
  at 
  home 
  in 
  the 
  Bahamas 
  and 
  which 
  find 
  

   no 
  permanent 
  place 
  in 
  the 
  New 
  England 
  fauna. 
  In 
  like 
  fashion, 
  

   young 
  fishes 
  from 
  the 
  Tropics 
  drift 
  northward 
  in 
  the 
  Kuro-Shiwo 
  

   (Black 
  Current) 
  to 
  the 
  coasts 
  of 
  Japan, 
  but 
  never 
  finding 
  a 
  perma- 
  

   nent 
  breeding 
  place 
  and 
  never 
  joining 
  the 
  ranks 
  of 
  the 
  Japanese 
  

   fishes. 
  But 
  to 
  this 
  there 
  have 
  been, 
  and 
  will 
  be, 
  occasional 
  excep- 
  

   tions. 
  Now 
  and 
  then 
  one 
  among 
  thousands 
  finds 
  permanent 
  lodg- 
  

   ment, 
  and 
  by 
  such 
  means 
  a 
  species 
  from 
  another 
  region 
  will 
  be 
  

  

  