﻿322 
  br 
  davy's 
  observations 
  on 
  the 
  charr. 
  

  

  pressure 
  applied 
  to 
  the 
  abdomen, 
  soon 
  after 
  the 
  fish 
  were 
  taken 
  from 
  the 
  water, 
  — 
  

   the 
  roe 
  in 
  detached 
  ova, 
  the 
  milt 
  in 
  the 
  state 
  of 
  a 
  milk-like 
  fluid. 
  

  

  It 
  was 
  from 
  these 
  boxes 
  that 
  I 
  obtained, 
  through 
  the 
  kindness 
  of 
  their 
  pro- 
  

   prietor, 
  most 
  of 
  the 
  subjects 
  of 
  the 
  following 
  observations; 
  and 
  to 
  him, 
  too, 
  I 
  was 
  

   indebted 
  for 
  exact 
  particulars, 
  without 
  which 
  the 
  observations 
  would 
  have 
  been 
  

   almost 
  valueless. 
  

  

  1. 
  Of 
  the 
  Roe 
  and 
  Milt 
  of 
  the 
  Charr. 
  

  

  The 
  ova 
  of 
  the 
  charr, 
  at 
  their 
  full 
  time, 
  that 
  is, 
  when 
  they 
  are 
  detached 
  from 
  

   their 
  ovaries, 
  and 
  are 
  loose 
  in 
  the 
  cavity 
  of 
  the 
  abdomen, 
  ready 
  for 
  expulsion, 
  are, 
  

   like 
  those 
  of 
  the 
  other 
  Salmonidse, 
  almost, 
  if 
  not 
  quite, 
  spherical. 
  Those 
  I 
  have 
  

   examined, 
  I 
  have 
  found 
  to 
  vary 
  in 
  diameter 
  from 
  -16 
  to 
  -18 
  and 
  -20 
  of 
  an 
  inch 
  ; 
  

   and 
  in 
  weight 
  (after 
  the 
  removal 
  of 
  adhering 
  moisture 
  by 
  wiping) 
  from 
  -7 
  grain 
  

   to 
  1 
  grain 
  each. 
  Their 
  colour 
  is 
  a 
  light 
  yellow, 
  lighter 
  than 
  that 
  of 
  the 
  ova 
  of 
  

   the 
  salmon 
  or 
  lake 
  trout 
  with 
  which 
  I 
  have 
  compared 
  them, 
  and 
  thus 
  distinguish- 
  

   able, 
  as 
  well 
  as 
  by 
  their 
  somewhat 
  smaller 
  size. 
  The 
  matter 
  of 
  which 
  they 
  con- 
  

   sist 
  may 
  be 
  described 
  as 
  an 
  almost 
  colourless, 
  transparent, 
  viscid 
  fluid, 
  contain- 
  

   ing 
  suspended 
  in 
  it 
  very 
  many 
  oil 
  globules 
  of 
  various 
  sizes, 
  hardly 
  distinguishable 
  

   without 
  the 
  aid 
  of 
  the 
  microscope, 
  of 
  a 
  yellow 
  colour, 
  to 
  which 
  the 
  colour 
  of 
  the 
  

   egg 
  is 
  principally 
  owing. 
  This 
  matter 
  may 
  be 
  considered 
  as 
  corresponding 
  to 
  

   the 
  yolk 
  of 
  the 
  egg 
  of 
  the 
  bird 
  : 
  it 
  is 
  more 
  than 
  doubtful 
  that 
  the 
  ova 
  of 
  the 
  

   charr 
  have 
  any 
  part 
  corresponding 
  to 
  the 
  albumen 
  of 
  the 
  bird's 
  egg. 
  The 
  matter 
  

   of 
  the 
  charr's 
  egg, 
  I 
  may 
  remark, 
  like 
  that 
  of 
  the 
  ova 
  of 
  the 
  Salmonidae 
  generally, 
  

   is 
  peculiar 
  in 
  some 
  of 
  its 
  properties 
  ; 
  being 
  coagulable 
  on 
  admixture 
  with 
  water, 
  

   as 
  I 
  believe 
  was 
  first 
  pointed 
  out 
  by 
  M. 
  Vogt, 
  in 
  the 
  instance 
  of 
  the 
  Coregonus 
  of 
  

   the 
  Lake 
  of 
  Neuchatel,* 
  — 
  in 
  being, 
  as 
  I 
  have 
  found, 
  not 
  coagulable 
  by 
  heat, 
  even 
  

   at 
  a 
  temperature 
  of 
  212' 
  Fahr., 
  if 
  water 
  be 
  excluded,— 
  in 
  being, 
  after 
  coagulation 
  

   by 
  water, 
  soluble 
  in 
  a 
  solution 
  of 
  common 
  salt 
  and 
  in 
  other 
  saline 
  solutions, 
  and 
  

   also 
  in 
  such 
  of 
  the 
  vegetable 
  acids 
  as 
  were 
  tried, 
  for 
  instance, 
  the 
  tartaric, 
  acetic, 
  

   oxalic, 
  and 
  citric. 
  For 
  a 
  fuller 
  account 
  of 
  these 
  experiments, 
  I 
  may 
  refer 
  to 
  a 
  

   paper 
  expressly 
  on 
  this 
  subject, 
  which 
  has 
  been 
  communicated 
  to 
  the 
  Royal 
  So- 
  

   ciety 
  of 
  London, 
  the 
  results 
  of 
  which 
  would 
  seem 
  to 
  show 
  that 
  the 
  substance 
  of 
  

   the 
  egg 
  of 
  the 
  Salmonidse 
  may 
  be 
  viewed 
  as 
  a 
  distinct 
  species 
  of 
  albumen, 
  — 
  as 
  

   much 
  so, 
  perhaps, 
  as 
  the 
  coagulable 
  lymph 
  of 
  the 
  blood 
  compared 
  with 
  the 
  serum 
  

   of 
  that 
  fluid. 
  

  

  The 
  shell 
  of 
  the 
  egg 
  of 
  the 
  charr 
  may 
  be 
  briefly 
  noticed. 
  Nearly 
  transparent 
  

   and 
  colourless, 
  it 
  is 
  of 
  considerable 
  strength, 
  and 
  until 
  thinned 
  and 
  weakened 
  in 
  

   the 
  process 
  of 
  hatching, 
  is 
  not 
  easily 
  ruptured. 
  Five 
  emptied 
  of 
  their 
  contents, 
  

   but 
  not 
  deprived 
  of 
  their 
  moisture 
  by 
  drying, 
  weighed 
  one-tenth 
  of 
  a 
  grain 
  ; 
  tho- 
  

  

  * 
  See 
  " 
  Enibryologie 
  des 
  Salmones. 
  Par 
  C. 
  Vogt.'' 
  Neuchatel, 
  1842, 
  4to, 
  p. 
  11. 
  

  

  