﻿384 
  ANNUAL 
  KEPOET 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  colored 
  perches, 
  whose 
  structure 
  is 
  especially 
  modified 
  for 
  life 
  on 
  the 
  

   rocky 
  bottoms 
  of 
  small 
  clear 
  streams. 
  The 
  relations 
  of 
  these 
  species 
  

   to 
  the 
  typical 
  perches 
  have 
  been 
  admirably 
  discussed 
  by 
  Prof. 
  Ste- 
  

   phen 
  A. 
  Forbes, 
  from 
  wliose 
  paper 
  ^^ 
  I 
  make 
  the 
  following 
  quotations 
  : 
  

  

  We 
  must 
  inquire, 
  therefore, 
  into 
  the 
  causes 
  which 
  have 
  operated 
  on 
  a 
  group 
  

   of 
  percoids 
  to 
  limit 
  their 
  range 
  to 
  such 
  apparently 
  unfavorable 
  conditions, 
  to 
  

   diminish 
  their 
  size, 
  to 
  develop 
  unduly 
  the 
  paired 
  fins 
  and 
  reduce 
  the 
  air-bladder, 
  

   to 
  remove 
  the 
  scales 
  of 
  several 
  species 
  more 
  or 
  less 
  completely, 
  * 
  * 
  * 
  and 
  to 
  

   restrict 
  their 
  food 
  chiefly 
  to 
  a 
  few 
  forms 
  (of 
  insect 
  larvse 
  and 
  Crustacea). 
  

  

  No 
  species 
  can 
  long 
  maintain 
  itself 
  anywhere 
  which 
  can 
  not 
  in 
  some 
  way 
  find 
  

   a 
  sufficient 
  food 
  supply 
  and 
  also 
  protect 
  itself 
  against 
  its 
  enemies. 
  In 
  its 
  con- 
  

   tests 
  with 
  its 
  enemies 
  it 
  may 
  acquire 
  defensive 
  structures 
  or 
  powers 
  of 
  escape 
  

   sufficient 
  for 
  its 
  protection, 
  or 
  it 
  may 
  become 
  adapted 
  to 
  some 
  place 
  of 
  refuge 
  

   where 
  other 
  fishes 
  will 
  not 
  follow. 
  What 
  better 
  refuge 
  could 
  a 
  harassed 
  fish 
  

   desire 
  than 
  the 
  hiding 
  places 
  among 
  stones 
  in 
  the 
  shallows 
  of 
  a 
  stream 
  where 
  

   the 
  water 
  dashes 
  ceaselessly 
  by 
  with 
  a 
  swiftness 
  few 
  fish 
  can 
  stem? 
  And 
  if 
  at 
  

   the 
  same 
  time 
  the 
  refugee 
  develop 
  a 
  swimming 
  power 
  which 
  enables 
  it 
  to 
  dart 
  

   like 
  a 
  flash 
  against 
  the 
  strongest 
  current, 
  its 
  safety 
  would 
  seem 
  to 
  be 
  insured. 
  

   But 
  what 
  food 
  could 
  it 
  find 
  in 
  such 
  a 
  place? 
  Let 
  us 
  turn 
  over 
  the 
  stones 
  in 
  

   such 
  a 
  stream, 
  sweeping 
  the 
  roiled 
  water 
  at 
  the 
  same 
  time 
  with 
  a 
  small 
  cloth 
  

   net, 
  and 
  we 
  shall 
  find 
  larva 
  of 
  Chironomus 
  and 
  small 
  Ephermerids, 
  and 
  other 
  

   such 
  prey 
  and 
  little 
  else 
  — 
  food 
  too 
  minute 
  and 
  difficult 
  of 
  access 
  to 
  support 
  a 
  

   large 
  fish, 
  but 
  answering 
  very 
  well 
  if 
  our 
  immigrant 
  can 
  keep 
  down 
  his 
  size. 
  

   * 
  * 
  * 
  The 
  limited 
  supply 
  of 
  food 
  early 
  arrests 
  the 
  growth 
  of 
  the 
  young; 
  

   while 
  every 
  fish 
  which 
  passes 
  the 
  allowable 
  maximum 
  is 
  forced 
  for 
  food 
  to 
  

   brave 
  the 
  dangers 
  of 
  the 
  deeper 
  waters, 
  where 
  the 
  chances 
  are 
  that 
  it 
  falls 
  a 
  

   prey. 
  On 
  the 
  other 
  hand, 
  the 
  smaller 
  the 
  size 
  of 
  those 
  vpith 
  this 
  alternative, 
  

   the 
  less 
  likely 
  will 
  they 
  be 
  to 
  attract 
  the 
  appetite 
  of 
  the 
  small 
  gar 
  or 
  other 
  

   guerilla, 
  which 
  may 
  occasionally 
  raid 
  their 
  retreat, 
  and 
  the 
  more 
  easily 
  will 
  

   they 
  slip 
  about 
  under 
  stones 
  in 
  search 
  of 
  their 
  microscopic 
  game. 
  

  

  Like 
  other 
  fishes, 
  the 
  darters 
  must 
  have 
  their 
  periods 
  of 
  repose, 
  all 
  the 
  more 
  

   urgent 
  because 
  of 
  the 
  constant 
  struggle 
  with 
  the 
  swift 
  current 
  which 
  their 
  

   habitat 
  imposes. 
  Shut 
  out 
  from 
  the 
  deep, 
  still 
  pools 
  and 
  slow 
  eddies 
  where 
  the 
  

   larger 
  species 
  lurk, 
  they 
  are 
  forced 
  to 
  spend 
  their 
  leisure 
  on 
  or 
  beneath 
  the 
  

   bottom 
  of 
  the 
  stream, 
  resting 
  on 
  their 
  extended 
  ventrals 
  and 
  anal 
  or 
  wholly 
  

   buried 
  in 
  the 
  sand. 
  * 
  * 
  * 
  

  

  Doubtless 
  the 
  search 
  for 
  food 
  has 
  much 
  to 
  do 
  with 
  this 
  selection 
  in 
  a 
  habitat. 
  

   I 
  have 
  found 
  that 
  the 
  young 
  of 
  nearly 
  all 
  species 
  of 
  our 
  fresh-water 
  fishes 
  

   are 
  competitors 
  for 
  food, 
  feeding 
  almost 
  entirely 
  on 
  Entomostraca 
  and 
  the 
  larv«e 
  

   of 
  minute 
  Diptera. 
  As 
  a 
  tree 
  sends 
  out 
  its 
  roots 
  in 
  all 
  directions 
  in 
  search 
  of 
  

   nourishment, 
  so 
  each 
  of 
  the 
  larger 
  divisions 
  of 
  aniihals 
  extends 
  its 
  various 
  

   groups 
  into 
  every 
  place 
  where 
  available 
  food 
  occurs, 
  each 
  group 
  becoming 
  

   adapted 
  to 
  the 
  special 
  features 
  of 
  its 
  situation. 
  Given 
  this 
  supply 
  of 
  certain 
  

   kinds 
  of 
  food, 
  nearly 
  inaccessible 
  to 
  the 
  ordinary 
  ^ph- 
  it 
  is 
  to 
  be 
  expected 
  that 
  

   some 
  fishes 
  would 
  become 
  especially 
  fitted 
  to 
  its 
  utilization. 
  Thus 
  the 
  Etheos- 
  

   tomidw 
  (darters) 
  as 
  a 
  group 
  are 
  to 
  be 
  explained 
  in 
  a 
  word 
  by 
  the 
  hypothesis 
  

   of 
  progressive 
  adaptation 
  of 
  the 
  young 
  of 
  certain 
  Percidce 
  to 
  a 
  peculiar 
  place 
  of 
  

   refuge 
  and 
  a 
  peculiar 
  food 
  supply. 
  

  

  Perhaps 
  we 
  may 
  without 
  violence 
  call 
  these 
  the 
  mountaineers 
  among 
  fishes. 
  

   Forced 
  from 
  the 
  populous 
  and 
  fertile 
  valleys 
  of 
  the 
  river 
  beds 
  and 
  lake 
  bottoms, 
  

   they 
  have 
  taken 
  refuge 
  from 
  their 
  enemies 
  in 
  the 
  rocky 
  highlands, 
  where 
  the 
  

  

  "A 
  catalogue 
  of 
  the 
  native 
  fishes 
  of 
  niinois. 
  Report 
  of 
  the 
  Illinois 
  Fish 
  Commis- 
  

   sioners, 
  1884, 
  p. 
  95. 
  

  

  