﻿aut.19 
  CONCERNING 
  BIRDS 
  ' 
  TONGUES 
  GARDNER 
  31 
  

  

  the 
  genus 
  Passerculus 
  the 
  grooving 
  is 
  very 
  marked 
  so 
  that 
  in 
  some 
  

   of 
  the 
  species 
  a 
  rolled 
  or 
  tubular 
  tongue 
  is 
  formed 
  (see 
  fig. 
  137 
  Pas- 
  

   serculus 
  rostratus) 
  . 
  

  

  In 
  conclusion 
  it 
  is 
  obvious 
  that 
  the 
  tongues 
  of 
  birds 
  subserve 
  

   many 
  different 
  uses, 
  a 
  wide 
  range 
  of 
  function 
  that 
  is 
  paralleled 
  by 
  

   changes 
  in 
  form, 
  ranging 
  from 
  simple 
  rudimentary 
  nodules 
  of 
  flesh 
  

   to 
  the 
  highly 
  complex 
  multiple 
  tongues 
  of 
  the 
  flower- 
  frequenting 
  

   birds. 
  Furthermore, 
  when 
  classified 
  as 
  to 
  adaptations, 
  eight 
  natural 
  

   groups 
  are 
  formed, 
  to 
  which 
  many 
  of 
  these 
  differing 
  patterns 
  may 
  

   be 
  assigned. 
  

  

  The 
  type 
  pattern 
  of 
  tongue 
  is 
  composed 
  of 
  a 
  fleshy 
  basal 
  part 
  

   which 
  is 
  tipped 
  with 
  a 
  more 
  or 
  less 
  extensive 
  thin 
  horny 
  translucent 
  

   anterior 
  portion, 
  which 
  has 
  an 
  inherent 
  tendency 
  to 
  curl, 
  bifurcate, 
  

   and 
  fray 
  laterally. 
  One 
  or 
  all 
  of 
  these 
  tendencies 
  are 
  utilized 
  to 
  

   produce 
  many 
  adaptive 
  modifications, 
  a 
  fine 
  series 
  of 
  which 
  may 
  be 
  

   traced 
  through 
  the 
  flower-frequenting 
  birds, 
  where 
  they 
  undergo 
  

   the 
  greatest 
  development, 
  producing 
  elaborate 
  and 
  complex 
  tubular, 
  

   brushy, 
  and 
  multiple 
  tongues. 
  

  

  Fundamentally 
  the 
  tongue 
  is 
  a 
  paired 
  structure 
  arising, 
  as 
  it 
  

   does, 
  from 
  the 
  second 
  and 
  third 
  visceral 
  arches, 
  and 
  upon 
  this 
  founda- 
  

   tion 
  must 
  be 
  constructed 
  all 
  the 
  variations 
  seen. 
  Practically, 
  how- 
  

   ever, 
  in 
  the 
  fully 
  developed 
  organ 
  the 
  alterations 
  have 
  become 
  so 
  

   great, 
  through 
  fusion 
  of 
  some 
  parts 
  and 
  suppression 
  or 
  exaggeration 
  

   of 
  others, 
  that 
  it 
  is 
  not 
  possible 
  to 
  select 
  a 
  fundamental 
  pattern 
  from 
  

   which 
  all 
  others 
  may 
  be 
  derived, 
  but, 
  instead, 
  many 
  of 
  these 
  must 
  be 
  

   recognized. 
  

  

  With 
  regard 
  to 
  the 
  taxonomic 
  value 
  of 
  this 
  organ 
  in 
  birds 
  the 
  evi- 
  

   dence 
  is 
  conflicting. 
  Much 
  of 
  it 
  tends 
  to 
  support 
  the 
  conclusion 
  

   that 
  it 
  is 
  of 
  little 
  or 
  no 
  value, 
  since, 
  either 
  from 
  similarity 
  of 
  diet 
  

   or' 
  due 
  to 
  convergent 
  evolution, 
  appearances 
  of 
  affinity 
  are 
  formed 
  

   where 
  no 
  true 
  relationship 
  exists. 
  Furthermore, 
  differences 
  in 
  struc- 
  

   ture 
  are 
  seen 
  in 
  closely 
  allied 
  birds 
  where 
  presumably 
  the 
  diet 
  is 
  the 
  

   same. 
  

  

  On 
  the 
  other 
  hand, 
  in 
  many 
  families, 
  in 
  spite 
  of 
  changes 
  in 
  re- 
  

   sponse 
  to 
  diet 
  a 
  uniform 
  and 
  characteristic 
  pattern 
  is 
  traceable 
  

   which 
  gives 
  definite 
  indications 
  of 
  affinity 
  and 
  provides 
  valuable 
  

   taxonomic 
  features. 
  Among 
  the 
  groups 
  in 
  which 
  this 
  is 
  true 
  are 
  the 
  

   Ardeidae, 
  Phoenicopteridae, 
  Anatidae, 
  Picidae, 
  Trichoglossidae, 
  

   Buteonidae, 
  Falconidae, 
  Trochilidae, 
  and 
  possibly 
  the 
  Meliphagidae, 
  

   Bucconidae, 
  Ramphastidae, 
  Corvidae, 
  and 
  Nectariniidae. 
  To 
  these 
  

   with 
  more 
  study, 
  others 
  may 
  be 
  added. 
  

  

  