﻿HYBRIDS. 
  113 
  

  

  Experiments, 
  conducted 
  with 
  the 
  greatest 
  care, 
  were 
  

   instituted 
  by 
  Pfliiger 
  in 
  1882. 
  He 
  was 
  able 
  to 
  show 
  

   that 
  different 
  degrees 
  exist 
  in 
  the 
  action 
  of 
  the 
  sperma- 
  

   tozoa 
  upon 
  the 
  ova 
  of 
  different 
  species. 
  Thus 
  the 
  

   spermatozoon 
  of 
  a 
  newt 
  (Molge 
  aljoestris, 
  M. 
  vulgaris) 
  

   acted 
  upon 
  the 
  ovum 
  oi 
  Ranatemporavia 
  to 
  the 
  extent 
  

   of 
  producing 
  a 
  very 
  irregular 
  segmentation 
  ; 
  other 
  

   cross-fertilisations 
  between 
  various 
  frogs 
  and 
  toads 
  

   extended 
  to 
  the 
  formation 
  of 
  an 
  embryo, 
  of 
  a 
  tadpole, 
  

   or 
  finally 
  of 
  a 
  perfect 
  Batrachian. 
  These 
  interesting 
  

   experiments 
  were 
  continued 
  by 
  Pfliiger 
  and 
  W. 
  J. 
  

   Smith 
  in 
  1883, 
  and 
  by 
  Born 
  in 
  1883 
  and 
  1884. 
  

  

  At 
  first 
  Pfliiger 
  absolutely 
  failed 
  in 
  crossing 
  Bana 
  

   temjjoraria 
  and 
  B. 
  arvalis, 
  but 
  ultimately 
  both 
  he 
  and 
  

   Born 
  succeeded 
  in 
  obtaining 
  a 
  few 
  perfect 
  hybrids 
  (B. 
  

   temporaria 
  S 
  X 
  B. 
  arvalis 
  ? 
  ). 
  Born 
  also 
  obtained 
  

   perfect 
  hybrids 
  of 
  Bnfo 
  vulgaris 
  and 
  B. 
  viridis 
  crossed 
  

   in 
  both 
  directions; 
  and, 
  what 
  is 
  more 
  extraordinary, 
  

   a 
  few 
  embryos, 
  which 
  did 
  not 
  develop 
  beyond 
  the 
  

   hatching 
  period, 
  from 
  eggs 
  of 
  Bana 
  esculenta 
  fecun- 
  

   dated 
  by 
  Bufo 
  viridis. 
  

  

  More 
  extraordinary 
  still 
  is 
  a 
  case 
  mentioned 
  by 
  

   Heron-Royer. 
  In 
  March, 
  1881, 
  he 
  found 
  a 
  male 
  Bana 
  

   temporaria 
  pairing 
  with 
  a 
  Belohates 
  fuscus 
  which 
  had 
  

   begun 
  to 
  spawn. 
  Having 
  brought 
  home 
  the 
  short 
  

   band 
  of 
  eggs, 
  he 
  was 
  much 
  surprised 
  to 
  see 
  them 
  

   develop 
  quite 
  normally, 
  and 
  ultimately 
  produce 
  larvas 
  

   which 
  were 
  indistinguishable 
  from 
  those 
  of 
  Bana 
  tem- 
  

   poraria 
  ; 
  and 
  two 
  that 
  survived 
  transformed 
  into 
  

   normal 
  specimens 
  of 
  B. 
  tem/poraria. 
  I 
  cannot 
  help 
  

   thinking 
  that 
  some 
  confusion 
  must 
  have 
  taken 
  place 
  : 
  

   may 
  not, 
  somehow 
  or 
  other, 
  embryos 
  of 
  B. 
  temporaria 
  

   have 
  been 
  substituted 
  whilst 
  Heron-Royer 
  was 
  observ- 
  

   ing 
  their 
  development 
  ? 
  

  

  Hybrids 
  between 
  two 
  closely 
  allied 
  species, 
  Bom- 
  

   hinator 
  igneus 
  and 
  B. 
  pachypus, 
  were 
  obtained 
  by 
  

   Heron 
  -Roy 
  er, 
  and 
  a 
  second 
  generation 
  was 
  produced 
  

   by 
  crossing 
  these 
  hybrids 
  with 
  individuals 
  of 
  the 
  

   latter 
  species. 
  It 
  also 
  appears 
  from 
  remarks 
  made 
  

  

  H 
  

  

  