﻿DEVELOPMENT 
  AND 
  METAMORPHOSIS. 
  

  

  87 
  

  

  diagram, 
  copied 
  from 
  Thiele's 
  memoir, 
  sliows 
  roughly 
  

   the 
  shape 
  of 
  this 
  organ, 
  and 
  its 
  position 
  with 
  respect 
  

   to 
  the 
  mouth 
  at 
  the 
  close 
  of 
  the 
  first 
  larval 
  period. 
  

  

  W 
  

  

  A 
  

  

  Fig. 
  33. 
  

  

  D 
  

  

  f 
  J 
  

  

  E 
  

  

  Gt 
  

  

  H 
  

  

  A. 
  Discoglossus 
  pictus. 
  B. 
  Pelohates 
  fuscus. 
  c. 
  Bufo 
  vulgaris. 
  

   D. 
  Bufo 
  viridis. 
  e. 
  Rana 
  esculenta. 
  p. 
  Bana 
  temporaria. 
  

   G. 
  Hyla 
  arhorea. 
  h. 
  Bombinator 
  pachypus. 
  

  

  As 
  the 
  embryo 
  grows 
  the 
  tail 
  elongates 
  and 
  shows 
  

   a 
  muscular 
  portion 
  with 
  chevron-shaped 
  myotomes, 
  

   bordered 
  above 
  and 
  below 
  by 
  a 
  membranous 
  crest. 
  

   The 
  gills 
  become 
  digitate 
  or 
  branched 
  ; 
  the 
  olfactory 
  

   pits 
  shift 
  more 
  forward, 
  and 
  become 
  converted 
  into 
  

   functional 
  nostrils 
  communicating 
  with 
  the 
  mouth; 
  

   the 
  eye 
  may 
  be 
  detected 
  at 
  the 
  side 
  of 
  the 
  head, 
  

   appearing 
  first 
  as 
  a 
  pigmented 
  ring 
  under 
  the 
  trans- 
  

   parent 
  epidermis; 
  the 
  mouth 
  becomes 
  bordered 
  by 
  

   fleshy 
  lips 
  ; 
  the 
  anus 
  is 
  perforated 
  ; 
  and 
  the 
  larva 
  

   is 
  able 
  to 
  feed, 
  having 
  thus 
  far 
  subsisted 
  on 
  the 
  

   vitellus 
  contained 
  in 
  the 
  abdomen. 
  

  

  The 
  external 
  gills, 
  two 
  or 
  three 
  in 
  number 
  on 
  each 
  

   side, 
  the 
  second 
  and 
  third 
  often 
  rudimentary 
  and 
  con- 
  

   cealed 
  under 
  the 
  first, 
  are 
  largest 
  and 
  persist 
  longest 
  

   in 
  Bana 
  temjporaria. 
  In 
  this 
  species 
  and 
  in 
  the 
  toads 
  

   they 
  are 
  strongly 
  pigmented, 
  like 
  the 
  body 
  ; 
  in 
  most 
  

   others 
  they 
  are 
  not, 
  or 
  but 
  feebly, 
  pigmented. 
  A 
  little 
  

   smaller 
  but 
  likewise 
  branched 
  in 
  Bana 
  esculenta, 
  Bufo 
  

   vulgaris, 
  and 
  Discoglossus, 
  they 
  remain 
  very 
  short 
  and 
  

  

  