﻿254 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  The 
  eggs 
  are 
  extruded 
  by 
  tbo 
  female 
  and 
  are 
  fertilized 
  by 
  the 
  male 
  

   as 
  they 
  pass 
  out, 
  very 
  few 
  failing 
  to 
  be 
  impregnated. 
  The 
  i)rocess 
  of 
  

   oviposition 
  or 
  laying 
  continues 
  through 
  several 
  days, 
  and 
  during 
  this 
  

   period 
  several 
  hundred 
  eggs 
  may 
  be 
  deposited. 
  The 
  size 
  of 
  the 
  ova 
  

   varies 
  with 
  the 
  species, 
  but 
  averages 
  about 
  1.75 
  millimeters 
  (.07 
  inch) 
  

   in 
  diameter. 
  In 
  passing 
  down 
  the 
  oviduct 
  the 
  egg 
  receives 
  a 
  thin 
  

   coating 
  of 
  albuminous 
  material 
  ; 
  this 
  rapidly 
  swells 
  when 
  the 
  egg 
  enters 
  

   the 
  water 
  aiid 
  forms 
  the 
  well-known 
  gelatinous 
  mass 
  in 
  which 
  the 
  frog 
  

   eggs 
  are 
  always 
  found 
  imbedded. 
  The 
  toad's 
  eggs 
  are 
  laid 
  in 
  long 
  

   strings 
  and 
  are 
  readily 
  distinguishable. 
  The 
  salamander's 
  eggs 
  are 
  also 
  

   placed 
  in 
  the 
  water, 
  but 
  the 
  gelatinous 
  mass 
  is 
  somewhat 
  firmer 
  and 
  

   the 
  eggs 
  are 
  slightly 
  larger 
  than 
  the 
  frog's, 
  and 
  they 
  are 
  usually 
  

   deposited 
  somewhat 
  earlier. 
  

  

  The 
  eggs 
  begin 
  development, 
  under 
  favorable 
  circumstances, 
  as 
  soon 
  

   as 
  fertilized, 
  the 
  rapidity 
  depending 
  mainly 
  on 
  the 
  temperature 
  of 
  the 
  

   water; 
  incubation 
  is 
  much 
  retarded 
  by 
  cold, 
  and 
  some 
  seasons 
  many 
  

   eggs 
  are 
  killed 
  by 
  late 
  frosts. 
  At 
  first 
  the 
  upper 
  part 
  of 
  the 
  'eggs 
  is 
  

   black 
  and 
  the 
  lower 
  white, 
  but 
  the 
  rapid 
  growth 
  of 
  the 
  black 
  embryo 
  

   makes 
  the 
  entire 
  egg 
  dark. 
  The 
  egg, 
  which 
  is 
  at 
  first 
  spherical, 
  soon 
  

   becomes 
  ovoid. 
  In 
  from 
  4 
  to 
  30 
  days 
  the 
  tadpole 
  is 
  able 
  to 
  wriggle 
  

   out 
  of 
  its 
  gelatinous 
  envelope 
  and 
  shortly 
  attaches 
  itself 
  to 
  some 
  plant 
  

   or 
  other 
  support 
  by 
  means 
  of 
  a 
  sort 
  of 
  adhesive 
  organ 
  in 
  front 
  of 
  the 
  

   mouth. 
  At 
  first 
  the 
  mouth 
  and 
  anus 
  are 
  closed, 
  and 
  food 
  can 
  only 
  be 
  

   obtained 
  by 
  absorption, 
  tlie 
  first 
  food 
  consisting 
  of 
  the 
  gelatinous 
  egg- 
  

   envelope. 
  In 
  a 
  short 
  time 
  the 
  mouth 
  and 
  anus 
  become 
  functional, 
  the 
  

   alimentary 
  canal 
  lengthens, 
  and 
  macerated 
  animal 
  and 
  vegetable 
  matter 
  

   becomes 
  the 
  food. 
  The 
  prevalent 
  idea 
  that 
  the 
  tadpole 
  is 
  exclusively 
  

   vegetarian, 
  based 
  on 
  its 
  anatomical 
  structure, 
  horny 
  jaws, 
  and 
  long 
  

   intestine, 
  is 
  incorrect. 
  Recent 
  observations 
  have 
  shown 
  that 
  animal 
  

   matter 
  is 
  preferred 
  to 
  vegetable; 
  all 
  food 
  must 
  be 
  in 
  a 
  state 
  of 
  macera- 
  

   tion, 
  especial 
  fondness 
  for 
  dead 
  animals 
  being 
  shown. 
  

  

  Respiration 
  is 
  at 
  first 
  carried 
  on 
  by 
  means 
  of 
  external 
  gills. 
  They 
  

   are 
  soon 
  replaced 
  by 
  internal 
  structures 
  covered 
  by 
  opercula. 
  

  

  Rapidity 
  of 
  development 
  depends 
  upon 
  the 
  abundance 
  of 
  food 
  and 
  

   the 
  temperature 
  of 
  water. 
  The 
  most 
  favorable 
  conditions 
  are 
  a 
  shallow 
  

   pool, 
  readily 
  warmed 
  by 
  the 
  sun 
  and 
  well 
  stocked 
  with 
  organic 
  matter, 
  

   that 
  is, 
  an 
  old 
  pond. 
  In 
  this 
  stage 
  the 
  frogs 
  may 
  reach 
  a 
  length 
  of 
  

   several 
  inches, 
  the 
  bullfrog 
  tadpole 
  being 
  largest. 
  The 
  various 
  species 
  

   closely 
  resemble 
  each 
  other, 
  but 
  can 
  be 
  distinguished 
  after 
  some 
  expe- 
  

   rience 
  by 
  certain 
  points 
  of 
  mouth 
  structure, 
  size, 
  and 
  coloration. 
  

  

  In 
  a 
  period 
  varying 
  from 
  two 
  months 
  to 
  two 
  years 
  the 
  first 
  indication 
  

   of 
  the 
  adult 
  form 
  appears 
  in 
  the 
  protrusion 
  of 
  the 
  two 
  hind 
  legs. 
  The 
  

   forelegs 
  or 
  arms, 
  owing 
  to 
  their 
  being 
  concealed 
  by 
  the 
  gill 
  membranes, 
  

   are 
  much 
  later 
  in 
  coming 
  out. 
  

  

  As 
  the 
  legs 
  become 
  functional 
  the 
  tail 
  is 
  absorbed 
  and 
  furnishes 
  

   material 
  for 
  growth, 
  so 
  that 
  little 
  food 
  is 
  taken. 
  In 
  the 
  case 
  of 
  the 
  

   second-year 
  tadpole 
  the 
  capture 
  of 
  insects 
  is 
  begun 
  before 
  the 
  tail 
  is 
  

  

  