﻿DR 
  DAVY 
  S 
  OBSERVATIONS 
  ON 
  THE 
  CHARR. 
  323 
  

  

  roughly 
  dried, 
  so 
  as 
  to 
  expel 
  this 
  moisture, 
  they 
  were 
  reduced 
  from 
  -10 
  to 
  "07 
  of 
  

   a 
  grain, 
  thereby 
  denoting 
  a 
  large 
  proportion 
  of 
  solid 
  matter, 
  viz., 
  70 
  per 
  cent. 
  

  

  Whether 
  this 
  shell 
  in 
  its 
  sound 
  state, 
  before 
  putrefaction 
  has 
  commenced, 
  is 
  

   pervious 
  to 
  water, 
  seems 
  to 
  me 
  questionable 
  ; 
  and 
  also, 
  whether 
  the 
  internal 
  

   vitelline 
  membrane, 
  after 
  fecundation, 
  is 
  altogether 
  impermeable 
  by 
  it. 
  M. 
  Vogt 
  

   holds 
  that 
  the 
  shell 
  is 
  at 
  all 
  times 
  so 
  permeable, 
  but 
  the 
  vitelline 
  membrane, 
  

   after 
  impregnation, 
  never, 
  so 
  long 
  as 
  the 
  ovum 
  retains 
  its 
  vitality 
  ; 
  losing 
  which, 
  

   the 
  membrane, 
  he 
  infers, 
  no 
  longer 
  resists 
  the 
  transmission 
  of 
  water, 
  and 
  the 
  

   coagulation 
  of 
  the 
  fluid 
  yolk 
  takes 
  place 
  as 
  an 
  unavoidable 
  consequence. 
  I 
  might 
  

   assign 
  reasons 
  for 
  the 
  doubts 
  I 
  venture 
  to 
  entertain 
  on 
  these 
  points 
  ; 
  but 
  not 
  sure 
  

   that 
  they 
  would 
  be 
  considered 
  satisfactory, 
  or 
  that 
  the 
  points 
  themselves, 
  though 
  

   not 
  without 
  interest, 
  require 
  here 
  to 
  be 
  discussed, 
  I 
  shall 
  avoid 
  bringing 
  them 
  

   forward. 
  That 
  the 
  death 
  of 
  the 
  impregnated 
  ovum, 
  as 
  pointed 
  out 
  by 
  M. 
  Vogt, 
  is 
  

   clearly 
  indicated 
  by 
  the 
  coagulation 
  of 
  the 
  yolk, 
  from 
  the 
  penetration 
  of 
  water 
  into 
  

   its 
  substance, 
  is 
  certain. 
  But 
  there 
  is 
  another 
  indication 
  of 
  the 
  event, 
  and 
  not 
  less 
  

   certain, 
  viz., 
  the 
  adherence 
  of 
  the 
  lighter 
  oil 
  globules 
  to 
  the 
  vitelline 
  membrane, 
  

   preventing 
  thereby 
  their 
  change 
  of 
  place 
  with 
  a 
  change 
  of 
  position 
  of 
  the 
  ovum, 
  

   and 
  that 
  tendency 
  to 
  ascend 
  in 
  the 
  heavier 
  yolk 
  fluid 
  which 
  is 
  observable 
  whilst 
  

   vitality 
  lasts, 
  and 
  which 
  may 
  perhaps 
  be 
  considered 
  as 
  a 
  characteristic 
  of 
  it. 
  The 
  

   adhesion 
  of 
  the 
  oil 
  globules 
  alluded 
  to, 
  not 
  unfrequentVy 
  takes 
  place 
  in 
  eggs 
  which 
  

   retain 
  their 
  transparency. 
  In 
  no 
  instance 
  have 
  I 
  observed 
  any 
  traces 
  of 
  foetal 
  

   development 
  after 
  these 
  have 
  become 
  fixed, 
  or, 
  if 
  commenced, 
  any 
  further 
  pro- 
  

   gress. 
  Why 
  these 
  ova 
  do 
  not 
  become 
  opaque, 
  why 
  their 
  membranes 
  should 
  re- 
  

   main 
  impervious 
  to 
  water, 
  I 
  am 
  ignorant 
  ; 
  but 
  that 
  they 
  are 
  so, 
  must 
  be 
  inferred 
  

   from 
  the 
  circumstance, 
  that 
  when 
  ruptured, 
  and 
  their 
  contents 
  mixed 
  with 
  water, 
  

   coagulation 
  is 
  immediately 
  effected. 
  

  

  Relative 
  to 
  the 
  milt 
  or 
  spermatic 
  fluid 
  of 
  the 
  charr, 
  I 
  have 
  but 
  few 
  observa- 
  

   tions 
  to 
  offer, 
  the 
  examination 
  I 
  have 
  hitherto 
  made 
  of 
  it 
  not 
  having 
  been 
  minute, 
  

   except 
  very 
  partially. 
  Like 
  that 
  of 
  the 
  Salmonidse 
  generally, 
  in 
  its 
  mature 
  state 
  

   when 
  ready 
  to 
  be 
  shed, 
  it 
  is 
  a 
  milk-like 
  fluid, 
  slightly 
  viscid, 
  heavier 
  than 
  water, 
  

   and 
  containing, 
  diffused 
  through 
  it 
  (the 
  cause 
  of 
  its 
  milkiness) 
  a 
  vast 
  number 
  of 
  

   granules 
  (spermatozoa). 
  These 
  minute 
  bodies 
  are 
  nearly 
  spherical 
  in 
  form, 
  are 
  

   about 
  i^th 
  of 
  an 
  inch 
  in 
  diameter, 
  and 
  seem 
  to 
  move 
  spontaneously, 
  as 
  seen 
  

   under 
  the 
  microscope, 
  for 
  a 
  short 
  time 
  after 
  the 
  expulsion 
  of 
  the 
  fluid 
  from 
  the 
  

   live 
  fish. 
  Though 
  they 
  are 
  of 
  greater 
  specific 
  gravity 
  than 
  water, 
  yet, 
  owing 
  to 
  

   their 
  minuteness, 
  they 
  are 
  easily 
  diffused 
  and 
  suspended 
  in 
  this 
  fluid. 
  After 
  a 
  

   rest 
  of 
  two 
  hours, 
  water 
  rendered 
  turbid 
  by 
  the 
  addition 
  of 
  a 
  small 
  quantity 
  of 
  

   spermatic 
  fluid 
  had 
  not 
  become 
  clear, 
  even 
  towards 
  its 
  surface. 
  A 
  drop 
  placed 
  

   under 
  the 
  microscope 
  was 
  found 
  to 
  abound 
  in 
  spermatozoa. 
  Another 
  property 
  of 
  

   the 
  spermatic 
  fluid, 
  not 
  unworthy 
  of 
  mention, 
  is 
  the 
  remarkable 
  manner 
  in 
  which 
  

   it 
  resists 
  putrefaction. 
  Whether 
  the 
  spermatozoa 
  are 
  capable 
  or 
  not 
  of 
  impreg- 
  

  

  