﻿14 
  

  

  INTEODUCTION. 
  

  

  tlie 
  tarsus 
  is, 
  of 
  course, 
  part 
  of 
  the 
  foot 
  proper 
  ; 
  but 
  

   as 
  it 
  here 
  forms 
  a 
  distinct 
  segment, 
  the 
  term 
  foot 
  is 
  

   used 
  in 
  a 
  restricted 
  sense. 
  The 
  foofc 
  is 
  measured 
  from 
  

   the 
  base 
  of 
  the 
  metatarsal 
  tubercle 
  ; 
  it 
  has 
  five 
  elon- 
  

   gate 
  toes, 
  gradually 
  increasing 
  in 
  length 
  to 
  the 
  

   fourth, 
  the 
  fifth 
  being 
  again 
  shorter. 
  There 
  is 
  in 
  

   addition 
  a 
  rudimentary 
  sixth 
  toe, 
  the 
  so-called 
  p^m- 
  

   liallucVi 
  conspicuous 
  externally 
  in 
  the 
  form 
  of 
  a 
  

   tubercle 
  or 
  spur 
  at 
  the 
  base 
  of 
  the 
  inner 
  toe. 
  In 
  

   Pelobates 
  (Fig. 
  4, 
  b) 
  this 
  prsehallux 
  or 
  inner 
  metatarsal 
  

   tubercle 
  acquires 
  a 
  very 
  great 
  development, 
  is 
  covered 
  

   by 
  a 
  horny 
  sheath 
  with 
  sharp 
  cutting 
  edge, 
  and 
  serves 
  

   as 
  a 
  shovel 
  for 
  digging 
  in 
  the 
  soil. 
  There 
  is 
  often 
  

   another 
  tubercle 
  on 
  the 
  sole, 
  at 
  the 
  base 
  of 
  the 
  

   fourth 
  toe 
  ; 
  this 
  so-called 
  outer 
  metatarsal 
  tubercle 
  

   (Fig. 
  4, 
  c) 
  is 
  merely 
  a 
  thickening 
  of 
  the 
  integument. 
  

  

  Fig. 
  4. 
  

  

  A. 
  Hsmd 
  oi 
  Alytes 
  ohstetricans. 
  b. 
  Foot 
  of 
  Pelobates 
  fuscus. 
  c. 
  Foot 
  

   oi 
  Bvsfo 
  calamita 
  (lower 
  views). 
  

  

  Other 
  dermal 
  tubercles 
  are 
  usually 
  present, 
  more 
  or 
  less 
  

   developed, 
  single 
  (Fig. 
  6, 
  a, 
  p. 
  16) 
  or 
  paired 
  (Fig. 
  4, 
  c), 
  

   under 
  the 
  digits 
  at 
  the 
  articulations 
  between 
  the 
  

   phalanges 
  ; 
  they 
  are 
  called 
  subarticular 
  tubercles. 
  

   The 
  fingers 
  are 
  free 
  except 
  in 
  Hijla 
  arhorea, 
  in 
  which 
  

   they 
  are 
  provided 
  with 
  a 
  rudimentary 
  web. 
  The 
  toes 
  

   are 
  more 
  or 
  less 
  webbed 
  or 
  bordered 
  by 
  membranes 
  in 
  

   all 
  our 
  Batrachians, 
  but 
  the 
  extent 
  of 
  the 
  web 
  varies 
  

   greatly 
  according 
  to 
  the 
  species, 
  and 
  is 
  usually 
  more 
  

   developed 
  in 
  males 
  than 
  in 
  females, 
  especially 
  during 
  

   the 
  breeding 
  season. 
  The 
  web 
  is 
  usually 
  smooth 
  and 
  

   transparent 
  ; 
  it 
  is 
  thicker, 
  and 
  often 
  warty, 
  especially 
  

   towards 
  the 
  margin, 
  in 
  Biifo. 
  

  

  