﻿TADPOLES. 
  

  

  105 
  

  

  and 
  Alytes 
  ohstetricans, 
  in 
  which 
  these 
  organs 
  are 
  

   represented 
  by 
  dotted 
  Hnes. 
  In 
  addition 
  to 
  these 
  

   lines, 
  all 
  tadpoles 
  show 
  more 
  or 
  less 
  distinctly 
  a 
  small 
  

   whitish 
  gland 
  in 
  the 
  middle 
  of 
  the 
  head 
  between 
  the 
  

   eyes, 
  the 
  so-called 
  /ro7zfa^ 
  gland 
  ov 
  j[}ineal 
  gland 
  ^ 
  which 
  

   in 
  early 
  stages 
  is 
  connected 
  with 
  the 
  brain. 
  A 
  glan- 
  

   dular 
  streak 
  extending 
  from 
  the 
  nostril 
  towards 
  the 
  

   eye 
  is 
  the 
  lachrymal 
  canal. 
  

  

  The 
  presence 
  of 
  a 
  number 
  of 
  pulsating 
  lymph-sacs 
  

   has 
  lately 
  been 
  discovered 
  by 
  Weliky 
  on 
  each 
  side 
  of 
  

   the 
  dorsal 
  caudal 
  crest. 
  

  

  Pigmentary 
  Networh. 
  — 
  In 
  addition 
  to 
  the 
  ordinary 
  

   pigment-cells, 
  the 
  tadpoles 
  of 
  afew 
  genera 
  {Dlscoglossus, 
  

   Bombinator, 
  Pelodytes) 
  present 
  a 
  system 
  of 
  fine 
  black 
  

   lines, 
  most 
  apparent 
  on 
  the 
  caudal 
  crests 
  and 
  the 
  more 
  

   feebly 
  pigmented 
  parts 
  of 
  the 
  body, 
  which 
  afford 
  

   excellent 
  characters 
  for 
  their 
  identification. 
  It 
  is 
  a 
  

   fact 
  worthy 
  of 
  notice 
  that 
  when 
  the 
  end 
  of 
  the 
  tail 
  has 
  

   been 
  injured 
  these 
  pigmentary 
  lines 
  are 
  not 
  reproduced 
  

   on 
  the 
  regenerated 
  portion. 
  Their 
  aspect 
  is 
  shown 
  in 
  

   the 
  following 
  figures 
  (from 
  'P. 
  Z. 
  S.,' 
  1891), 
  repre- 
  

   senting 
  much-enlarged 
  pieces 
  of 
  the 
  upper 
  "caudal 
  

   crest 
  of 
  Pelodytes 
  (a) 
  and 
  Discoglossus 
  (b). 
  

  

  Fig. 
  47. 
  

  

  The 
  following 
  key 
  has 
  been 
  drawn 
  up 
  to 
  facilitate 
  

   the 
  identification 
  of 
  the 
  genera 
  and 
  species 
  in 
  the 
  tad- 
  

   pole 
  condition. 
  

  

  I. 
  Spiraculum 
  median 
  ; 
  anus 
  median 
  ; 
  tail 
  rounded 
  

   or 
  obtuse 
  at 
  the 
  end 
  ; 
  a 
  papillose 
  edge 
  all 
  round 
  

  

  