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  RANID2E. 
  

  

  Although 
  so 
  closely 
  allied 
  and 
  liviug 
  side 
  by 
  side 
  in 
  

   many 
  localities, 
  these 
  two 
  species 
  never 
  appear 
  to 
  in- 
  

   terbreed. 
  As 
  in 
  B. 
  temporaria 
  and 
  B. 
  arvalis, 
  this 
  is 
  

   probably 
  to 
  be 
  ascribed 
  mainly 
  to 
  the 
  great 
  difference 
  

   in 
  the 
  seminal 
  elements, 
  as 
  mentioned 
  on 
  p. 
  77 
  of 
  the 
  

   Introduction. 
  

  

  Eggs. 
  — 
  According 
  to 
  Count 
  Peracca, 
  to 
  whom 
  I 
  

   am 
  also 
  indebted 
  for 
  eggs 
  of 
  this 
  frog, 
  the 
  vitelline 
  

   sphere 
  is 
  blackish-brown, 
  with 
  the 
  lower 
  third 
  white, 
  

   and 
  measures 
  If 
  mm. 
  ; 
  the 
  mucilaginous 
  envelop 
  is 
  

   also 
  smaller 
  than 
  in 
  B. 
  agilis 
  and 
  B. 
  temporaria, 
  6 
  or 
  

  

  Fig. 
  120. 
  

  

  7 
  mm. 
  in 
  diameter. 
  The 
  embryo, 
  on 
  leaving 
  the 
  egg 
  

   on 
  the 
  thirteenth 
  or 
  fourteenth 
  day, 
  is 
  only 
  half 
  as 
  

   long 
  as 
  that 
  of 
  B. 
  agilis. 
  

  

  Tadpole 
  (PL 
  III, 
  fig. 
  6). 
  — 
  Intermediate 
  between 
  B. 
  

   temporaria 
  and 
  B. 
  agilis. 
  Width 
  of 
  mouth 
  equalling 
  

   the 
  distance 
  between 
  the 
  nostrils 
  and 
  two-thirds 
  the 
  

   distance 
  between 
  the 
  eyes. 
  Series 
  of 
  labial 
  teeth 
  f 
  , 
  

   the 
  second 
  upper 
  series 
  very 
  widely 
  interrupted 
  in 
  the 
  

   middle, 
  the 
  third 
  extremely 
  short 
  ; 
  first 
  lower 
  series 
  

   very 
  short, 
  hardly 
  half 
  the 
  length 
  of 
  the 
  second; 
  

   fourth 
  interrupted 
  in 
  the 
  middle. 
  Beak 
  as 
  in 
  B. 
  tem- 
  

   poraria. 
  Tail 
  acutely 
  pointed, 
  twice 
  as 
  long 
  as 
  the 
  

   body, 
  its 
  depth 
  one-third 
  its 
  length. 
  Lines 
  of 
  muci- 
  

   ferous 
  crypts 
  very 
  distinct, 
  as 
  in 
  B. 
  agilis. 
  

  

  Brown 
  above, 
  whitish 
  beneath 
  ; 
  caudal 
  crests 
  

   whitish, 
  dotted 
  with 
  dark 
  brown, 
  the 
  upper 
  with 
  

   some 
  larger 
  spots. 
  

  

  