﻿82 
  INTEODUCTION. 
  

  

  2. 
  Envelop 
  7 
  — 
  10 
  millimetres 
  in 
  diameter; 
  

  

  embryo 
  brown 
  or 
  blackish 
  . 
  . 
  . 
  Eana. 
  

  

  (a) 
  Vitellus 
  miparti, 
  brown 
  or 
  blackish 
  

  

  above, 
  yellowish 
  or 
  white 
  below, 
  or 
  

  

  the 
  light 
  spot 
  covering 
  at 
  least 
  the 
  

  

  lower 
  third 
  ; 
  eggs 
  submerged. 
  

  

  Diameter 
  of 
  vitellus 
  1^ 
  — 
  2 
  millimetres. 
  

  

  R. 
  esculenta, 
  R. 
  arvalis. 
  

   Diameter 
  of 
  vitellus 
  2 
  — 
  3 
  millimetres 
  . 
  R. 
  agilis. 
  

   {h) 
  Vitellus 
  nearly 
  entirely 
  black, 
  with 
  a 
  

   small 
  whitish 
  lower 
  pole. 
  

   Diameter 
  of 
  vitellus 
  2 
  — 
  3 
  millimetres 
  ; 
  eggs 
  float- 
  

   ing 
  R. 
  temjjoraria. 
  

  

  Diameter 
  of 
  vitellus 
  1^ 
  — 
  If 
  millimetres; 
  eggs 
  

  

  submerged 
  R. 
  latastii. 
  

  

  It 
  may 
  be 
  noticed 
  that, 
  so 
  far 
  as 
  species 
  are 
  con- 
  

   cerned, 
  the. 
  size 
  of 
  the 
  egg 
  stands 
  in 
  no 
  relation 
  to 
  

   that 
  of 
  the 
  parent, 
  a 
  fact 
  which 
  is 
  also 
  conspicuous 
  in 
  

   the 
  tadpole. 
  Thus 
  the 
  largest 
  Batrachian, 
  B^ifo 
  vul- 
  

   garis, 
  has 
  eggs 
  no 
  larger 
  than 
  the 
  smallest, 
  Pelo- 
  

   dytes 
  punctatus 
  ; 
  and 
  in 
  Rana 
  temporaria 
  they 
  are 
  

   considerably 
  larger 
  than 
  in 
  R. 
  esculenta, 
  which 
  reaches 
  

   both 
  in 
  the 
  larval 
  and 
  perfect 
  states 
  to 
  a 
  much 
  greater 
  

   size. 
  Heron-Royer 
  has 
  observed 
  that 
  young 
  females 
  

   produce 
  eggs 
  of 
  a 
  somewhat 
  smaller 
  size 
  than 
  those 
  

   of 
  full-grown 
  specimens 
  of 
  the 
  same 
  species, 
  arid 
  I 
  

   have 
  been 
  able 
  to 
  verify 
  his 
  observation 
  on 
  Rana 
  

   temporaria. 
  

  

  The 
  number 
  of 
  eo^o^s 
  also 
  varies 
  accordinof- 
  to 
  the 
  

   size 
  of 
  the 
  female. 
  Heron-Royer, 
  who 
  has 
  counted 
  

   them 
  in 
  most 
  of 
  the 
  European 
  species, 
  gives 
  the 
  

   following 
  numbers 
  as 
  the 
  result 
  of 
  his 
  computation 
  : 
  

   Bufo 
  viridis 
  ..... 
  10,000—12,000 
  

  

  Rana 
  esculenta 
  

   Bufo 
  vulgaris 
  . 
  

   Bufo 
  calamita 
  . 
  

   Rana 
  teniptoraria 
  

   Pelohates 
  fuscus 
  

   Rana 
  arvalis 
  . 
  

  

  10,000 
  

  

  4,972— 
  6,840 
  

   3,000— 
  4,000 
  

   2,856— 
  4,005 
  

   1,200— 
  2,236 
  

   1,000— 
  2,000 
  

  

  