﻿112 
  JNTEODUCTION. 
  

  

  XIV. 
  Hybeids. 
  

  

  The 
  fact, 
  so 
  often 
  observed, 
  that 
  pairiug 
  takes 
  place 
  

   between 
  different 
  species 
  — 
  as, 
  for 
  instance, 
  between 
  

   Rana 
  temporaria 
  and 
  Bufo 
  vulgaris, 
  Bana 
  temporaria 
  

   and 
  Pelohates 
  fuscus, 
  Felodytes 
  punctatus 
  and 
  Hyla 
  

   arhorea 
  — 
  has 
  long 
  ago 
  given 
  rise 
  to 
  the 
  supposition 
  

   that 
  hybrids 
  are 
  occasionally 
  produced. 
  At 
  the 
  end 
  

   of 
  the 
  last 
  century, 
  Spallanzani, 
  after 
  his 
  successful 
  

   experiments 
  on 
  artificial 
  fecundation, 
  attempted 
  to 
  

   raise 
  hybrids 
  between 
  species 
  of 
  Bana, 
  Biifo, 
  and 
  

   Hyla, 
  but 
  without 
  results. 
  

  

  Experiments 
  w^ere 
  again 
  instituted, 
  from 
  1867 
  to 
  

   1872, 
  by 
  A. 
  de 
  I'lsle, 
  who 
  tried 
  to 
  hybridise 
  the 
  

   French 
  species 
  of 
  Bana 
  and 
  Bufo. 
  The 
  difficulty 
  of 
  

   such 
  experiments 
  is 
  very 
  great, 
  owing 
  to 
  the 
  diversity 
  

   in 
  the 
  breeding 
  season 
  of 
  the 
  different 
  species. 
  Never- 
  

   theless 
  de 
  risle 
  succeeded 
  in 
  procuring 
  suitable 
  ex- 
  

   amples 
  of 
  three 
  species 
  of 
  Bana, 
  and 
  artificially 
  

   impregnated 
  ova 
  of 
  Bana 
  esculenta 
  and 
  B. 
  agilis 
  with 
  

   the 
  semen 
  of 
  B. 
  teviporaria, 
  and 
  ova 
  of 
  Bana 
  tem- 
  

   poraria 
  with 
  the 
  semen 
  of 
  the 
  two 
  others. 
  The 
  ex- 
  

   periments, 
  several 
  times 
  repeated, 
  gave 
  a 
  negative 
  

   result, 
  which 
  the 
  author 
  attributes 
  to 
  the 
  very 
  con- 
  

   siderable 
  difi*erence 
  between 
  the 
  genital 
  organs 
  of 
  even 
  

   so 
  closely 
  allied 
  species 
  as 
  B. 
  temjporaria 
  and 
  B. 
  agilis. 
  

   But 
  with 
  Bufo 
  vulgaris 
  and 
  B. 
  calamita, 
  which, 
  

   although 
  morjDhologically 
  more 
  widely 
  separated, 
  

   have 
  almost 
  identical 
  genitalia, 
  positive 
  results 
  were 
  

   obtained, 
  although 
  the 
  development 
  did 
  not 
  proceed 
  

   beyond 
  the 
  tadpole 
  condition. 
  

  

  A 
  few 
  years 
  later, 
  in 
  1877 
  and 
  1878, 
  the 
  subject 
  

   was 
  again 
  taken 
  up 
  by 
  Lataste, 
  who 
  succeeded 
  in 
  

   fertilisino' 
  eofofs 
  of 
  Pelohates 
  fuscus 
  with 
  the 
  semen 
  of 
  

   p. 
  cultripes. 
  But 
  the 
  few 
  tadpoles 
  obtained 
  were 
  

   monstrous 
  or 
  dropsical, 
  and 
  not 
  one 
  survived 
  to 
  

   develop 
  the 
  limbs. 
  

  

  