﻿DR 
  DAVY 
  S 
  OBSERVATIONS 
  ON 
  THE 
  CHARR. 
  325 
  

  

  seldom 
  below 
  54° 
  and 
  never 
  above 
  50°. 
  On 
  the 
  10th 
  of 
  December 
  two 
  young 
  fish 
  

   left 
  their 
  shells, 
  and 
  on 
  the 
  following 
  day 
  a 
  third. 
  They 
  were 
  all 
  three 
  feeble, 
  as 
  

   if 
  their 
  development 
  had 
  been 
  premature 
  ; 
  in 
  a 
  few 
  days 
  they 
  died. 
  Some 
  eggs 
  

   from 
  the 
  same 
  fish 
  which 
  had 
  been 
  placed 
  in 
  Mr 
  Reynold's 
  breeding 
  boxes 
  were 
  

   not 
  hatched 
  till 
  the 
  90th 
  day, 
  or 
  more 
  than 
  double 
  the 
  time. 
  

  

  What 
  the 
  other 
  circumstances 
  are— 
  other 
  than 
  that 
  of 
  mere 
  difference 
  of 
  tem- 
  

   perature 
  — 
  which 
  influence 
  the 
  acceleration 
  or 
  retardation 
  of 
  the 
  hatching 
  process, 
  

   are 
  deserving 
  of 
  being 
  investigated 
  experimentally. 
  Something 
  may, 
  perhaps, 
  

   depend 
  on 
  the 
  size 
  and 
  quality 
  of 
  the 
  egg 
  ; 
  something 
  on 
  the 
  contact 
  of 
  the 
  sper- 
  

   matozoa, 
  their 
  number 
  and 
  activity 
  ; 
  and 
  other 
  conjectures 
  might 
  be 
  offered. 
  

  

  In 
  illustration 
  of 
  the 
  growth 
  of 
  the 
  young 
  fish, 
  after 
  quitting 
  the 
  egg, 
  I 
  shall 
  

   briefly 
  describe 
  what 
  I 
  witnessed 
  in 
  the 
  instances 
  of 
  three 
  that 
  I 
  observed 
  with 
  

   some 
  care 
  from 
  the 
  time 
  of 
  their 
  escape 
  from 
  the 
  shell 
  to 
  the 
  attainment 
  nearly 
  

   of 
  their 
  perfect 
  form. 
  It 
  was 
  on 
  the 
  17th 
  of 
  January 
  that 
  they 
  were 
  hatched. 
  

   Some 
  days 
  previously 
  the 
  embryos 
  were 
  very 
  active, 
  frequently 
  changing 
  their 
  

   position 
  by 
  sudden 
  jerks, 
  effected 
  by 
  the 
  tail 
  and 
  the 
  posterior 
  portion 
  of 
  the 
  body. 
  

   One 
  I 
  saw 
  in 
  the 
  act 
  of 
  bursting 
  the 
  shell, 
  now 
  become 
  very 
  thin 
  and 
  tender. 
  The 
  

   rupture 
  took 
  place 
  suddenly 
  at 
  a 
  spot 
  where 
  there 
  was 
  a 
  little 
  prominence, 
  — 
  an 
  

   evident 
  yielding 
  of 
  the 
  shell 
  to 
  the 
  pressure 
  from 
  within, 
  — 
  and 
  simultaneously 
  

   the 
  coiled-up 
  foetus 
  became 
  liberated 
  ; 
  the 
  effort, 
  it 
  may 
  be 
  inferred, 
  made 
  by 
  the 
  

   tail, 
  by 
  which 
  the 
  opening 
  was 
  made, 
  sufficing 
  to 
  extricate 
  it. 
  The 
  instant 
  the 
  

   young 
  fish 
  entered 
  the 
  water, 
  it 
  darted 
  about 
  wildly 
  for 
  a 
  few 
  seconds 
  ; 
  then 
  

   rested, 
  lying 
  on 
  its 
  side. 
  It 
  was 
  most 
  easily 
  disturbed 
  ; 
  on 
  the 
  slightest 
  touch, 
  

   even 
  if 
  merely 
  applied 
  to 
  the 
  water 
  near 
  it, 
  it 
  fled 
  from 
  the 
  touching 
  body, 
  moving 
  

   with 
  wonderful 
  rapidity, 
  and 
  in 
  such 
  an 
  irregular, 
  devious 
  course 
  as 
  was 
  well 
  

   adapted 
  to 
  promote 
  its 
  escape 
  from 
  a 
  pursuing 
  enemy. 
  

  

  These 
  fish 
  varied 
  in 
  length 
  from 
  about 
  six-tenths 
  to 
  seven-tenths 
  of 
  an 
  inch 
  ; 
  

   the 
  yolk 
  attached 
  was 
  about 
  -25 
  of 
  an 
  inch 
  in 
  length, 
  and 
  about 
  -15 
  of 
  an 
  inch 
  in 
  

   depth, 
  of 
  an 
  oval 
  form. 
  They 
  were 
  transparent 
  and 
  almost 
  colourless, 
  allowing 
  

   the 
  circulation 
  of 
  the 
  blood 
  to 
  be 
  seen 
  distinctly 
  with 
  the 
  microscope, 
  using 
  even 
  

   a 
  low 
  power, 
  such 
  as 
  a 
  glass 
  of 
  one-inch 
  focal 
  distance. 
  Their 
  eyes 
  appeared 
  to 
  

   be 
  perfect, 
  the 
  lens 
  visible 
  and 
  apparently 
  prominent, 
  the 
  iris 
  coloured 
  ; 
  and, 
  in 
  

   accordance, 
  the 
  vision 
  seemed 
  to 
  be 
  acute, 
  even 
  the 
  approach 
  of 
  a 
  moving 
  body, 
  

   without 
  coming 
  in 
  contact 
  with 
  the 
  water, 
  exciting 
  alarm, 
  indicated 
  by 
  a 
  sudden 
  

   change 
  of 
  place. 
  The 
  pectoral 
  fins 
  were 
  distinct 
  and 
  almost 
  constantly 
  in 
  action 
  ; 
  

   the 
  single 
  embryonic 
  fin 
  including 
  the 
  rounded 
  tail, 
  extended 
  inferiorly 
  to 
  the 
  yolk 
  

   sac, 
  and 
  superiorly 
  a 
  little 
  beyond 
  the 
  spot 
  where 
  the 
  dorsal 
  fin 
  was 
  to 
  be. 
  

  

  On 
  the 
  30th 
  of 
  January, 
  a 
  very 
  slight 
  increase 
  in 
  their 
  length 
  was 
  observable, 
  

   about 
  -02 
  of 
  an 
  inch. 
  The 
  several 
  fins, 
  the 
  dorsal, 
  the 
  abdominal, 
  and 
  anal, 
  were 
  

   beginning 
  to 
  appear 
  in 
  the 
  form 
  of 
  slight 
  projections 
  from 
  the 
  single 
  fin, 
  especially 
  

   the 
  dorsal, 
  in 
  which 
  rays 
  were 
  noticeable. 
  The 
  gill-covers 
  now 
  were 
  somewhat 
  

  

  VOL. 
  XX. 
  PART 
  III. 
  4 
  T 
  

  

  