﻿TADPOLES. 
  101 
  

  

  By 
  drawing 
  an 
  imaginary 
  line 
  across 
  between 
  the 
  

   mandibles 
  the 
  lip 
  may 
  be 
  divided 
  into 
  an 
  upper 
  and 
  a 
  

   lower 
  portion, 
  the 
  series 
  of 
  teeth 
  above 
  the 
  upper 
  

   mandible 
  being 
  termed 
  upper 
  lahial, 
  those 
  below 
  the 
  

   lower 
  mandible 
  beinsf 
  lower 
  labial. 
  These 
  are 
  described 
  

   as 
  first, 
  second, 
  third, 
  &c., 
  proceeding 
  from 
  the 
  outer 
  

   border 
  towards 
  the 
  beak 
  in 
  both 
  the 
  upper 
  and 
  lower 
  

   sections 
  of 
  the 
  lip, 
  as 
  shown 
  in 
  the 
  accompanying 
  

   figures 
  (p. 
  99). 
  Each 
  series 
  is 
  reckoned 
  as 
  one, 
  

   whether 
  continuous 
  or 
  more 
  or 
  less 
  interrupted 
  in 
  the 
  

   middle; 
  this 
  method 
  being 
  far 
  more 
  simple, 
  and 
  at 
  the 
  

   same 
  time 
  more 
  correct, 
  considering 
  the 
  great 
  amount 
  

   of 
  individual 
  variation, 
  than 
  those 
  used 
  by 
  some 
  authors 
  

   who 
  distino^uish 
  between 
  "median" 
  and 
  "lateral" 
  

   series, 
  according 
  as 
  to 
  whether 
  or 
  not 
  the. 
  series 
  is 
  

   broken 
  up 
  in 
  the 
  middle. 
  The 
  first 
  series, 
  either 
  in 
  

   the 
  upper 
  or 
  lower 
  division 
  of 
  the 
  lip, 
  may 
  be 
  marginal 
  

   (Fig. 
  42, 
  A, 
  ^.1), 
  or 
  it 
  may 
  be 
  within 
  the 
  border, 
  

   which 
  is 
  then 
  occupied 
  by 
  fleshy 
  papillae 
  (Fig. 
  42, 
  

   e). 
  The 
  arrangement 
  of 
  the 
  series 
  is 
  expressed 
  

   by 
  a 
  formula 
  — 
  f, 
  for 
  instance, 
  indicating 
  the 
  number 
  

   in 
  the 
  upper 
  and 
  lower 
  divisions, 
  the 
  figures 
  being 
  

   separated 
  by 
  a 
  transverse 
  line 
  corresponding 
  to 
  the 
  

   position 
  of 
  the 
  horny 
  beak. 
  The 
  labial 
  teeth 
  are 
  

   usually 
  arranged 
  in 
  a 
  single 
  row 
  on 
  each 
  ridge 
  (Fig. 
  

   42, 
  a) 
  ; 
  in 
  the 
  Disco 
  glossidae, 
  however, 
  each 
  ridge, 
  or 
  at 
  

   any 
  rate 
  the 
  second, 
  bears 
  two 
  or 
  even 
  three 
  rows 
  of 
  

   teeth 
  (Fig. 
  42, 
  b). 
  The 
  beak 
  itself 
  is 
  made 
  up 
  of 
  

   horny 
  elements 
  like 
  the 
  labial 
  teeth 
  ; 
  its 
  edge, 
  when 
  

   sufficiently 
  magnified, 
  is 
  seen 
  to 
  be 
  denticulate, 
  each 
  

   denticle 
  representing 
  the 
  cusp 
  of 
  a 
  single 
  tooth. 
  

  

  The 
  inside 
  of 
  the 
  mouth 
  and 
  the 
  pharynx 
  (Fig. 
  44) 
  

   are 
  beset 
  with 
  long 
  pointed 
  mucous 
  papillse, 
  '' 
  taste- 
  

   organs" 
  of 
  F. 
  E. 
  Schulze, 
  the 
  longest 
  of 
  which 
  border 
  

   the 
  choanse 
  {cli)^ 
  one 
  in 
  front 
  and 
  one 
  behind, 
  and 
  are 
  

   followed 
  by 
  a 
  pair 
  with 
  a 
  denticulate 
  fold 
  between 
  

   them 
  ; 
  a 
  cushion-like, 
  hemispherical 
  swelling 
  {t) 
  repre- 
  

   sents 
  the 
  tongue, 
  on 
  the 
  anterior 
  border 
  of 
  which 
  a 
  

   pair 
  of 
  papillse 
  are 
  inserted. 
  A 
  broad 
  cleft 
  with 
  

  

  