﻿96 
  INTRODUCTION. 
  

  

  The 
  annexed 
  figure 
  (40) 
  of 
  the 
  vertebral 
  column 
  

   (ventral 
  aspect) 
  of 
  a 
  recently 
  transformed 
  Pelobates 
  

   cuUrijjes 
  shows 
  well 
  the 
  independence 
  of 
  the 
  inter- 
  

   vertebral 
  spheres 
  and 
  the 
  three 
  elements 
  which 
  enter 
  

   into 
  the 
  formation 
  of 
  the 
  urostyle. 
  

  

  A 
  glance 
  at 
  this 
  figure 
  will 
  also 
  

   Fig. 
  40. 
  show 
  to 
  what 
  extent 
  the 
  importance 
  

  

  of 
  the 
  mode 
  of 
  articulation 
  of 
  the 
  

   vertebrae 
  has 
  been 
  overrated 
  by 
  those 
  

   systematists 
  who 
  have 
  proposed 
  to 
  

   divide 
  the 
  tailless 
  Batrachians 
  pri- 
  

   marily 
  into 
  procoelian 
  and 
  opistho- 
  

   coelian 
  types. 
  As 
  a 
  matter 
  of 
  fact, 
  

   both 
  occur 
  in 
  the 
  family 
  Pelohatidse, 
  

   some 
  of 
  the 
  exotic 
  genera 
  of 
  which 
  

   are 
  normally 
  opisthocoelian. 
  

  

  During 
  larval 
  life 
  the 
  habits 
  vary 
  

   considerably 
  according 
  to 
  the 
  species. 
  

   Thus 
  Hyla 
  is 
  always 
  on 
  the 
  move, 
  

   swimming 
  about 
  in 
  every 
  direction 
  like 
  a 
  fish 
  ; 
  Bom- 
  

   hinator, 
  Ahjtes, 
  Pelobates, 
  and 
  Baiia 
  keep 
  more 
  to 
  

   the 
  bottom, 
  approaching 
  the 
  borders 
  of 
  the 
  ponds 
  

   or 
  pools 
  during 
  the 
  hotter 
  part 
  of 
  the 
  day 
  to 
  sun 
  

   themselves 
  in 
  shallow 
  water 
  ; 
  Discoglossus, 
  Pelodytes, 
  

   and 
  Bufo 
  are 
  in 
  the 
  habit 
  of 
  coming 
  frequently 
  to 
  

   take 
  air 
  on 
  the 
  surface, 
  where 
  they 
  swim 
  about 
  with 
  

   upturned 
  bellies. 
  

  

  The 
  notion 
  that 
  tadpoles 
  are 
  exclusively 
  herbivorous 
  

   has 
  long 
  been 
  exploded 
  ; 
  they 
  feed 
  on 
  both 
  vegetable 
  

   and 
  animal 
  substances, 
  and 
  usually 
  show 
  a 
  preference 
  

   for 
  the 
  latter, 
  in 
  addition 
  to 
  the 
  microscopical 
  organ- 
  

   isms 
  contained 
  in 
  the 
  ooze, 
  which 
  they 
  swallow 
  in 
  large 
  

   quantities. 
  Their 
  carnivorous 
  or 
  even 
  cannibal 
  habits 
  

   are 
  only 
  too 
  noticeable 
  in 
  confinement, 
  and 
  they 
  have 
  

   been 
  utilised 
  for 
  making 
  small 
  and 
  delicate 
  skeletons. 
  

   The 
  tadpoles 
  of 
  Bomhinator 
  and 
  Alytes 
  are 
  almost 
  

   exclusively 
  carnivorous, 
  the 
  real 
  difference 
  between 
  

   them 
  and 
  the 
  perfect 
  animal 
  being 
  that 
  the 
  former 
  

   feed 
  readily 
  on 
  dead 
  or 
  even 
  decomposing 
  matter, 
  

  

  