﻿HYBRIDISATION 
  IN 
  LEPIDOPTERA. 
  15 
  

  

  an 
  absolute 
  inability 
  to 
  thus 
  produce 
  fertile 
  progeny, 
  as 
  from 
  the 
  great 
  

   difficulty, 
  owing 
  to 
  changed 
  habits, 
  etc., 
  of 
  the 
  forms 
  ever 
  coming 
  

   in 
  contact 
  sufficiently 
  to 
  allow 
  it. 
  When 
  the 
  change 
  of 
  habit 
  is 
  accom- 
  

   panied 
  by 
  a 
  morphological 
  or 
  functional 
  change, 
  and 
  when 
  the 
  forms 
  

   have 
  been 
  farther 
  isolated 
  by 
  the 
  loss 
  of 
  the 
  most 
  closely 
  allied 
  indi- 
  

   viduals, 
  the 
  anatomical 
  and 
  functional 
  differences 
  existing 
  between 
  the 
  

   species 
  may 
  be 
  so 
  great 
  as 
  to 
  absolutely 
  prevent 
  crossing 
  or 
  the 
  pro- 
  

   duction 
  of 
  fertile 
  offspring. 
  If 
  it 
  be 
  accepted 
  that 
  species 
  have 
  thus 
  

   been 
  formed 
  by 
  the 
  slow 
  accumulation 
  of 
  differences 
  in 
  habit, 
  accom- 
  

   panied 
  with 
  an 
  ever-increasing 
  difference 
  in 
  anatomy 
  and 
  function, 
  

   then 
  the 
  ease 
  or 
  difficulty 
  of 
  hybridising 
  allied 
  species 
  may 
  indicate 
  

   the 
  actual 
  amount 
  of 
  difference 
  and 
  distinctness 
  of 
  the 
  species 
  on 
  

   which 
  experiments 
  are 
  made. 
  

  

  It 
  has, 
  however, 
  long 
  been 
  a 
  matter 
  of 
  discussion 
  as 
  to 
  how 
  far 
  the 
  

   actual 
  hybridity 
  of 
  species 
  may 
  itself 
  be 
  an 
  active 
  factor 
  in 
  the 
  formation 
  

   of 
  new 
  species, 
  i.e., 
  how 
  far 
  hybrids 
  are 
  capable 
  of 
  forming 
  a 
  new 
  

   species. 
  Standfuss 
  discusses 
  (Ent., 
  xxxiii., 
  pp. 
  240 
  et 
  seq.) 
  this 
  question 
  

   and 
  considers 
  that 
  the 
  experiments 
  that 
  he 
  has 
  already 
  undertaken 
  

   have 
  largely 
  answered 
  the 
  question 
  in 
  the 
  negative. 
  Even 
  when 
  

   hybridity 
  is 
  not 
  difficult 
  to 
  procure 
  between 
  two 
  species, 
  the 
  progeny 
  

   shows 
  little 
  fertility 
  inter 
  se, 
  and, 
  although 
  the 
  $ 
  s 
  are 
  more 
  frequently 
  

   fertile 
  with 
  $ 
  s 
  of 
  either 
  of 
  the 
  parent 
  species, 
  the 
  $ 
  hybrids 
  are 
  

   much 
  more 
  rarely 
  fertile 
  with 
  the 
  Js 
  of 
  the 
  parent 
  species, 
  and 
  at 
  

   present 
  few 
  hybrids 
  show 
  comparatively 
  free 
  fertility 
  inter 
  se. 
  This 
  

   appears 
  to 
  be 
  largely 
  due 
  to 
  the 
  anatomical 
  and 
  morphological 
  upset 
  

   in 
  the 
  sexual 
  organs 
  of 
  the 
  $ 
  hybrids, 
  an 
  upset 
  that 
  frequently 
  finds 
  its 
  

   outward 
  recognition 
  in 
  the 
  development 
  of 
  gynandromorphic 
  forms, 
  in 
  

   which 
  the 
  primary 
  sexual 
  characters 
  are 
  often 
  considerably 
  modified, 
  

   and 
  correspondingly 
  marked 
  changes 
  take 
  place 
  in 
  the 
  secondary 
  

   sexual 
  characters. 
  

  

  Assuming, 
  however, 
  hybridity 
  ever 
  to 
  take 
  place 
  in 
  nature, 
  the 
  

   hybrids 
  themselves 
  will 
  often, 
  presumably, 
  foliow 
  one 
  or 
  other 
  of 
  the 
  parent 
  

   forms 
  so 
  far 
  as 
  relates 
  to 
  its 
  habits, 
  time 
  of 
  appearance, 
  etc., 
  and 
  the 
  

   chance 
  of 
  a 
  $ 
  and 
  $ 
  hybrid, 
  assuming 
  that 
  some 
  of 
  both 
  sexes 
  get 
  

   through 
  successfully, 
  then 
  meeting 
  each 
  other, 
  as 
  against 
  the 
  possibility 
  of 
  

   either 
  meeting 
  and 
  pairing 
  with 
  or 
  being 
  paired 
  with 
  a 
  $ 
  or 
  2 
  of 
  the 
  

   much 
  more 
  abundant 
  parent 
  form, 
  is 
  so 
  remote 
  that 
  one 
  puts 
  aside 
  the 
  

   possibility 
  ; 
  one 
  suspects 
  that 
  such 
  individuals 
  as 
  survived 
  would 
  

   almost 
  certainly 
  pair 
  with 
  one 
  of 
  the 
  parent 
  forms 
  and 
  the 
  hybrid 
  

   characters 
  (if 
  any 
  marked 
  ones 
  occurred) 
  would 
  be 
  bred 
  out 
  in 
  two 
  or 
  

   three 
  generations. 
  As 
  illustrating 
  this 
  point, 
  we 
  captured, 
  on 
  May 
  20th, 
  

   1893, 
  a 
  $ 
  specimen 
  of 
  what 
  we 
  have 
  no 
  doubt 
  is 
  Polyommatus 
  corydon 
  

   xbellan/ns, 
  at 
  Cuxton, 
  with 
  the 
  shape 
  and 
  contour 
  of 
  corydon, 
  but 
  

   with 
  the 
  unmistakable 
  colouring 
  of 
  bellargus 
  in 
  it. 
  It 
  was 
  flying 
  

   among 
  hundreds 
  of 
  bellargus 
  and 
  was 
  paired 
  with 
  a 
  typical 
  bellargus 
  ? 
  . 
  

   No 
  doubt 
  exists 
  in 
  our 
  mind 
  that 
  this 
  was 
  a 
  cross 
  between 
  an 
  early 
  

   emerged 
  August 
  specimen 
  of 
  bellargus 
  of 
  the 
  preceding 
  year 
  with 
  a 
  late 
  

   emerged 
  August 
  specimen 
  of 
  corydon. 
  It 
  had 
  evidently 
  followed 
  the 
  

   habit 
  of 
  bellargus, 
  had 
  emerged 
  with 
  the 
  early 
  spring 
  brood 
  of 
  that 
  

   species, 
  had 
  paired 
  with 
  a 
  typical 
  ? 
  bellargus, 
  and 
  its 
  progeny 
  would, 
  

   one 
  suspects, 
  if 
  any, 
  have 
  reverted 
  to 
  ordinary 
  bellargus 
  in. 
  at 
  most, 
  a 
  

   few 
  generations, 
  although 
  in 
  appearance 
  the 
  specimen 
  is 
  much 
  more 
  

   like 
  corydon. 
  Possibly 
  following 
  Standfuss' 
  conclusions 
  the 
  male 
  parent 
  

  

  