﻿358 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  the 
  lake 
  by 
  its 
  actual 
  ancestors. 
  No. 
  2 
  is 
  illustrated 
  by 
  the 
  dis- 
  

   appearance 
  of 
  East 
  Indian 
  types 
  {Zcmclus, 
  Platax, 
  Toxotes, 
  etc.) 
  

   from 
  Italy 
  at 
  the 
  end 
  of 
  the 
  Eocene, 
  perhaps 
  for 
  climatic 
  reasons. 
  

   Extinction 
  through 
  competition 
  is 
  shown 
  in 
  the 
  gradual 
  disappear- 
  

   ance 
  of 
  the 
  Sacramento 
  perch 
  {Archoplites 
  interruptus) 
  after 
  the 
  

   invasion 
  of 
  the 
  river 
  by 
  catfish 
  and 
  carp. 
  From 
  extreme 
  specializa- 
  

   tion 
  certain 
  forms 
  have 
  disappeared, 
  but 
  no 
  certain 
  case 
  of 
  this 
  kind 
  

   has 
  been 
  pointed 
  out 
  among 
  fishes, 
  unless 
  this 
  be 
  the 
  cause 
  of 
  the 
  

   disappearance 
  of 
  the 
  Devonian 
  mailed 
  Ostracophores 
  and 
  Arthro- 
  

   dires, 
  or 
  of 
  various 
  types 
  modified 
  by 
  orthogenesis. 
  It 
  is 
  not 
  likely 
  

   that 
  any 
  group 
  of 
  fishes 
  has 
  ever 
  perished 
  through 
  exhaustion 
  of 
  

   the 
  stock 
  of 
  vigor. 
  Exhaustion 
  is 
  an 
  individual 
  not 
  a 
  collective 
  

   matter. 
  

  

  We 
  are 
  now 
  learning 
  in 
  some 
  detail 
  the 
  methods 
  of 
  transmutation 
  

   of 
  species, 
  the 
  adjustment 
  in 
  nature 
  of 
  new 
  forms, 
  and 
  I 
  do 
  not 
  need 
  

   to 
  discuss 
  the 
  matter 
  here. 
  Suffice 
  it 
  to 
  say 
  that 
  natural 
  selection 
  en- 
  

   forces 
  not 
  separation 
  but 
  adaptation, 
  in 
  which 
  all 
  forms 
  which 
  main- 
  

   tain 
  themselves 
  must 
  share, 
  and 
  no 
  variations, 
  however 
  favorable, 
  

   can 
  crowd 
  out 
  the 
  original 
  stock, 
  which 
  must 
  have 
  the 
  advantages 
  of 
  

   long-continued 
  heredity, 
  and 
  at 
  the 
  beginning, 
  at 
  least, 
  the 
  likelihood 
  

   of 
  being 
  smothered 
  by 
  crossbreeding. 
  I 
  do 
  not 
  believe 
  that 
  any 
  new 
  

   and 
  permanent 
  species 
  was 
  ever 
  established 
  in 
  nature 
  by 
  any 
  form 
  of 
  

   mutation 
  or 
  discontinuous 
  variation 
  or 
  that 
  any 
  variation 
  really 
  dis- 
  

   continuous 
  ever 
  occurs. 
  Neither 
  is 
  there 
  any 
  serious 
  evidence 
  that 
  

   new 
  species 
  are 
  ever 
  formed 
  in 
  nature 
  by 
  any 
  hybridism, 
  Mendelian, 
  

   or 
  otherwise. 
  The 
  various 
  phases 
  of 
  Mendelism 
  concern 
  heredity, 
  

   but 
  not 
  to 
  any 
  great 
  extent 
  the 
  methods 
  of 
  species 
  forming. 
  A 
  

   species, 
  as 
  I 
  understand 
  it, 
  is 
  a 
  definable 
  group 
  of 
  animals 
  or 
  plants 
  

   produced 
  in 
  the 
  natural 
  divergence 
  of 
  life, 
  which 
  has 
  run 
  the 
  gauntlet 
  

   of 
  time 
  and 
  which 
  has 
  endured. 
  The 
  problem 
  of 
  the 
  origin 
  of 
  species 
  

   relates 
  to 
  forms 
  which 
  have 
  lasted. 
  

  

  That 
  most 
  genera 
  of 
  sea 
  fishes 
  of 
  Miocene 
  times 
  and 
  their 
  species 
  

   have 
  passed 
  away 
  is 
  evident 
  to 
  students 
  of 
  paleontology. 
  That 
  the 
  

   living 
  faunas 
  are 
  in 
  general 
  made 
  up 
  of 
  the 
  same 
  elements 
  as 
  in 
  

   Miocene 
  times 
  is 
  also 
  evident, 
  these 
  elements 
  belonging 
  mostly 
  to 
  the 
  

   same 
  families, 
  though 
  rarely 
  to 
  the 
  same 
  genera. 
  That 
  shore 
  fishes 
  

   become 
  extinct 
  with 
  time 
  is 
  evident, 
  though 
  the 
  causes 
  for 
  their 
  dis- 
  

   appearance 
  are 
  largely 
  hypothetical. 
  The 
  chief 
  of 
  them 
  is 
  the 
  altera- 
  

   tion 
  of 
  external 
  conditions, 
  climate 
  sometimes, 
  sometimes 
  the 
  appear- 
  

   ance 
  of 
  new 
  friends 
  or 
  new 
  enemies, 
  changing 
  the 
  conditions 
  of 
  life 
  by 
  

   placing 
  a 
  new 
  or 
  different 
  stress 
  on 
  the 
  breeding 
  of 
  the 
  species. 
  Other 
  

   causes 
  are 
  often 
  suggested 
  and 
  some 
  may 
  have 
  a 
  degree 
  of 
  value. 
  

   Among 
  these 
  are 
  the 
  modifications 
  due 
  to 
  progressive 
  evolution, 
  what- 
  

   ever 
  that 
  may 
  be; 
  but 
  we 
  may 
  well 
  look 
  with 
  doubt 
  on 
  alleged 
  

  

  