﻿HABITS. 
  57 
  

  

  YII. 
  Habits. 
  

  

  Frogs 
  and 
  toads 
  ivere 
  classified 
  by 
  the 
  earlier 
  authors 
  

   into 
  terrestrial, 
  aquatic, 
  and 
  arboreal. 
  It 
  would 
  be 
  

   difficult 
  now, 
  nay 
  impossible, 
  to 
  draw 
  any 
  sharp 
  demar- 
  

   cation 
  line 
  between 
  the 
  tbree 
  types, 
  and 
  all 
  we 
  can 
  do 
  

   is 
  to 
  emphasise 
  the 
  differences 
  which 
  exist 
  between 
  the 
  

   extreme 
  forms. 
  Thus 
  by 
  opposing 
  the 
  extremes 
  we 
  

   can 
  show 
  examples 
  among 
  the 
  European 
  representa- 
  

   tives 
  of 
  terrestrial 
  and 
  aquatic 
  (Alytes 
  ohstetricans 
  — 
  

   Uaiia 
  esculenta), 
  fossorial 
  and 
  scansorial 
  {Pelohates 
  — 
  

   Hyla), 
  saltatorial 
  and 
  cursorial 
  {Bana 
  agilis 
  — 
  Biifo 
  

   calamita), 
  diurnal 
  and 
  nocturnal 
  [Raiia 
  esculenta 
  — 
  

   Alytes 
  ohstetricans) 
  types, 
  which 
  are, 
  however, 
  con- 
  

   nected 
  by 
  insensible 
  gradations. 
  These 
  adaptations 
  

   are 
  revealed 
  by 
  certain 
  structural 
  characters, 
  such 
  as 
  

   the 
  development 
  of 
  the 
  web 
  between 
  the 
  toes 
  to 
  facili- 
  

   tate 
  natation, 
  the 
  great 
  development 
  of 
  the 
  inner 
  

   metatarsal 
  tubercle 
  to 
  assist 
  in 
  burrowing, 
  the 
  adhesive 
  

   digital 
  disks 
  for 
  chmbing, 
  the 
  relative 
  length 
  of 
  the 
  

   hind 
  limbs 
  for 
  jumping, 
  and 
  the 
  shape 
  of 
  the 
  pupil, 
  

   whether 
  round 
  or 
  horizontal 
  or 
  vertical, 
  as 
  indicative 
  

   of 
  more 
  or 
  less 
  diurnal 
  or 
  essentially 
  nocturnal 
  habits. 
  

   But 
  here 
  and 
  there 
  we 
  meet 
  with 
  exceptions; 
  such 
  

   are, 
  for 
  instance, 
  the 
  fully 
  -webbed 
  toes 
  of 
  Pelohates, 
  

   which 
  spends 
  but 
  a 
  short 
  time 
  of 
  the 
  year 
  in 
  the 
  

   water; 
  the 
  shovel-shaped 
  metatarsal 
  tubercle 
  of 
  Bana 
  

   esculenta, 
  var. 
  lessonse, 
  which 
  does 
  not 
  burrow; 
  or 
  the 
  

   similarity 
  in 
  shape 
  of 
  the 
  pupil 
  in 
  Bana 
  and 
  Bnfo, 
  

   which 
  yet 
  differ 
  so 
  much 
  in 
  their 
  habits. 
  Still, 
  on 
  the 
  

   whole 
  we 
  may 
  roughly 
  incorporate 
  the 
  species 
  outside 
  

   the 
  breeding 
  season 
  into 
  the 
  following 
  categories 
  : 
  

  

  Diurnal 
  and 
  aquatic 
  : 
  B^ana 
  esculenta, 
  Discoglossus, 
  

   Bomhinator. 
  

  

  Diurnal 
  and 
  terrestrial 
  : 
  Bana 
  temporaria 
  and 
  allies. 
  

  

  IN^octurnal 
  and 
  terrestrial 
  : 
  Bufo, 
  Pelodytes, 
  Alytes. 
  

  

  Nocturnal 
  and 
  fossorial 
  : 
  Pelohates. 
  

  

  Nocturnal 
  and 
  arboreal 
  : 
  Hyla. 
  

  

  That 
  most, 
  though 
  not 
  all, 
  are 
  aquatic 
  during 
  the 
  

  

  