﻿EANA. 
  311 
  

  

  tadpoles 
  are 
  still 
  to 
  be 
  found 
  in 
  August, 
  and 
  are 
  even 
  

   sometimes 
  compelled 
  to 
  hibernate 
  in 
  that 
  condition. 
  

  

  Many 
  observers 
  who 
  have 
  kept 
  pairing 
  frogs 
  of 
  

   this 
  species 
  in 
  confinement 
  have 
  been 
  disappointed 
  at 
  

   finding 
  the 
  eggs 
  laid 
  under 
  these 
  conditions 
  to 
  be 
  

   unfertilised, 
  this 
  being 
  often 
  the 
  case 
  when 
  single 
  

   pairs 
  are 
  confined 
  in 
  jars, 
  and 
  apparently 
  due 
  to 
  the 
  

   male 
  not 
  emitting 
  his 
  fecundating 
  fluid 
  at 
  the 
  right 
  

   moment. 
  Fischer-Sigwart 
  has 
  recently 
  attempted 
  to 
  

   explain 
  this 
  fact 
  by 
  suggesting 
  that 
  the 
  males 
  fecundate 
  

   the 
  eggs 
  some 
  time 
  after 
  they 
  are 
  laid 
  and 
  after 
  the 
  

   release 
  of 
  the 
  females 
  from 
  embrace. 
  I 
  cannot 
  accept 
  

   this 
  explanation, 
  because 
  I 
  have 
  observed, 
  in 
  prac- 
  

   tising 
  artificial 
  insemination, 
  that 
  the 
  spermatozoa 
  

   appear 
  to 
  be 
  unable 
  to 
  penetrate 
  the 
  eggs 
  after 
  the 
  

   mucilaginous 
  capsules 
  have 
  become 
  swollen 
  out 
  with 
  

   water, 
  which 
  takes 
  place 
  very 
  rapidly 
  after 
  deposition. 
  

   In 
  order 
  to 
  fully 
  satisfy 
  my 
  mind 
  on 
  this 
  point, 
  I 
  

   made 
  this 
  spring 
  (March 
  22nd) 
  the 
  following 
  experi- 
  

   ment. 
  

  

  At 
  11 
  a.m. 
  I 
  pressed 
  into 
  two 
  dishes 
  filled 
  with 
  

   water 
  from 
  the 
  supply-tap 
  a 
  few 
  eggs 
  (about 
  fifty 
  in 
  

   each 
  dish) 
  from 
  a 
  female 
  held 
  in 
  embrace. 
  The 
  pair 
  

   were 
  then 
  separated 
  and 
  kept 
  dry 
  until 
  2 
  p.m., 
  when 
  

   the 
  male 
  was 
  killed 
  and 
  the 
  fluid 
  removed 
  from 
  the 
  

   vesicula 
  seminis, 
  whilst 
  two 
  further 
  small 
  lots 
  of 
  eggs 
  

   were 
  pressed 
  out 
  of 
  the 
  female 
  into 
  the 
  dishes 
  in 
  

   which 
  lay 
  those 
  previously 
  obtained, 
  with 
  their 
  cap- 
  

   sules 
  now 
  considerably 
  inflated. 
  I 
  then 
  poured 
  the 
  

   seminal 
  fluid, 
  diluted 
  in 
  a 
  wineglassful 
  of 
  water, 
  over 
  

   the 
  four 
  clumps 
  of 
  eggs. 
  The 
  result 
  was 
  the 
  same 
  in 
  

   both 
  dishes 
  : 
  the 
  eggs 
  laid 
  at 
  11 
  a.m. 
  and 
  fecundated 
  

   at 
  2 
  p.m. 
  did 
  not 
  develop 
  (with 
  one 
  and 
  two 
  excep- 
  

   tions 
  respectively), 
  whilst 
  the 
  great 
  majority 
  of 
  the 
  

   others 
  underwent 
  their 
  normal 
  evolution. 
  

  

  Eggs. 
  — 
  Yitellus 
  measuring 
  2 
  to 
  3 
  mm. 
  in 
  diameter, 
  

   black, 
  with 
  a 
  small 
  white 
  or 
  grey 
  spot 
  on 
  the 
  lower 
  

   pole; 
  mucilaginous 
  envelop 
  measuring 
  8 
  to 
  10 
  mm. 
  

   in 
  diameter. 
  The 
  eggs 
  form 
  one 
  or 
  two 
  large 
  balls, 
  

  

  