﻿NO. 
  1134. 
  PHILJPPIXE 
  ORyiTHOLOGT—WOECESTEn 
  AXD 
  BOUEXS. 
  615 
  

  

  era, 
  but 
  as 
  the 
  islands 
  grow 
  larger 
  it 
  becomes 
  increasingly 
  common 
  to 
  

   find 
  two 
  or 
  more 
  species 
  of. 
  a 
  genus 
  in 
  a 
  place. 
  

  

  Although 
  this 
  curve 
  does 
  not 
  rise 
  quite 
  so 
  high 
  for 
  Luzon 
  as 
  did 
  

   ' 
  Curve 
  II, 
  its 
  general 
  level 
  is 
  well 
  up, 
  owing 
  to 
  the 
  fact 
  that 
  due 
  impor- 
  

   tance 
  is 
  given 
  to 
  the 
  number 
  of 
  species 
  aftbrding 
  exceptions 
  to 
  the 
  law, 
  

   which 
  has 
  not 
  been 
  done 
  in 
  the 
  other 
  curves. 
  

  

  Perhaps 
  the 
  most 
  conclusive 
  of 
  all 
  the 
  curves 
  is 
  Curve 
  V, 
  where 
  ihe 
  

   islands 
  are 
  arranged 
  according 
  to 
  the 
  number 
  of 
  species 
  in 
  Tables 
  A 
  

   and 
  B 
  recorded 
  from 
  each. 
  

  

  These 
  last 
  two 
  curves 
  make 
  it 
  evident 
  that 
  even 
  when 
  Steere's 
  law 
  

   is 
  given 
  the 
  benefit 
  of 
  the 
  doubt 
  in 
  every 
  case, 
  which 
  is 
  most 
  illogical, 
  

   there 
  still 
  remains 
  for 
  all 
  but 
  the 
  very 
  smallest 
  and 
  least 
  known 
  islands 
  

   a 
  mass 
  of 
  exceptions 
  altogether 
  too 
  ibrmidable 
  to 
  be 
  overlooked; 
  that 
  

   the 
  percentage 
  of 
  exceptions 
  steadily 
  increases 
  with 
  increase 
  in 
  the 
  

   number 
  of 
  species 
  recorded, 
  and 
  that 
  finally 
  in 
  the 
  largest 
  and 
  best 
  

   known 
  islands 
  it 
  is 
  no 
  less 
  than 
  73 
  per 
  cent 
  of 
  the 
  whole 
  number 
  of 
  

   species 
  considered. 
  

  

  It 
  remains 
  to 
  be 
  ascertained 
  whether 
  the 
  genera 
  of 
  Tables 
  A 
  and 
  B 
  

   group 
  themselves 
  into 
  separate 
  families, 
  or 
  whether 
  we 
  shall 
  find 
  that 
  

   in 
  the 
  majority 
  of 
  cases 
  some 
  genera 
  of 
  a 
  family 
  are 
  distributed 
  in 
  the 
  

   one 
  way, 
  others 
  in 
  the 
  other. 
  

  

  In 
  Curve 
  VI, 
  I 
  have 
  endeavored 
  to 
  bring 
  out 
  the 
  facts. 
  Families 
  

   are 
  arranged 
  in 
  horizontal 
  series, 
  space 
  being 
  given 
  to 
  each 
  propor- 
  

   tionate 
  to 
  the 
  number 
  of 
  genera 
  that 
  it 
  includes, 
  4 
  units 
  being 
  

   allowed 
  to 
  each 
  genus. 
  It 
  will 
  be 
  seen 
  that 
  in 
  fourteen 
  families 
  there 
  

   is 
  not 
  a 
  single 
  genus 
  of 
  resident 
  land 
  birds 
  with 
  but 
  one 
  species 
  in 
  an 
  

   island. 
  Seven 
  more 
  families 
  have 
  less 
  than 
  half 
  their 
  genera 
  distributed 
  

   according 
  to 
  Steere's 
  law 
  ; 
  three 
  have 
  their 
  genera 
  equally 
  divided 
  as 
  

   regards 
  the 
  method 
  of 
  their 
  distribution; 
  four 
  have 
  more 
  than 
  50 
  per 
  

   cent 
  distributed 
  according 
  to 
  the 
  law, 
  while 
  eight 
  have 
  all 
  their 
  species 
  

   so 
  distributed. 
  

  

  With 
  few 
  exceptions, 
  the 
  species 
  included 
  in 
  these 
  eight 
  families 
  are 
  

   possessed 
  of 
  comparatively^ 
  weak 
  power 
  of 
  fiight, 
  hence 
  are 
  unable 
  to 
  

   surmount 
  geographical 
  barriers 
  of 
  any 
  importance. 
  I 
  do 
  not 
  doubt 
  that 
  

   they 
  are 
  in 
  many 
  instances 
  to 
  be 
  regarded 
  as 
  geographical 
  races, 
  and 
  

   that 
  isolation 
  has 
  had 
  much 
  to 
  do 
  with 
  bringing 
  them 
  into 
  existence, 
  

   but 
  1 
  feel 
  indisposed 
  to 
  make 
  the 
  same 
  admission 
  for 
  all 
  the 
  species 
  

   belonging 
  to 
  the 
  fourteen 
  families 
  which 
  do 
  not 
  oifer 
  a 
  single 
  confirma- 
  

   tion 
  of 
  Steere's 
  law. 
  

  

  I 
  believe, 
  then, 
  that 
  in 
  formulating 
  his 
  law 
  Steere 
  has 
  given 
  alto- 
  

   gether 
  too 
  much 
  importance 
  to 
  a 
  really 
  important 
  factor 
  in 
  the 
  devel- 
  

   opment 
  of 
  species. 
  He 
  has 
  assigned 
  undue 
  prominence 
  to 
  geographical 
  

   barriers, 
  especially 
  sea 
  channels, 
  and 
  has 
  not 
  given 
  sufficient 
  consider- 
  

   ation 
  to 
  the 
  fact 
  that 
  within 
  the 
  confines 
  of 
  the 
  larger 
  islands, 
  especially 
  

   when 
  they 
  are 
  mountainous 
  and 
  well 
  wooded, 
  there 
  is 
  abundant 
  room 
  

   for 
  life 
  zones 
  which 
  may 
  be 
  quite 
  as 
  sharply 
  defined 
  as 
  those 
  marked 
  

   out 
  by 
  salt 
  water. 
  

  

  