﻿97 
  

  

  A 
  room 
  in 
  the 
  pleepiiig 
  barge 
  was 
  kindly 
  allotted 
  to 
  ray 
  

   use. 
  This 
  was 
  very 
  soon 
  converted 
  into 
  a 
  miniature 
  scientific 
  

   laboratory, 
  and 
  here 
  each 
  lot 
  of 
  ova 
  or 
  fry 
  was 
  taken, 
  examined 
  

   under 
  the 
  microscope, 
  drawings 
  made 
  of 
  the 
  different 
  stages, 
  

   and 
  then 
  tlie 
  specimens 
  were 
  placed 
  in 
  picric, 
  osraic, 
  or 
  chromic 
  

   acid 
  — 
  sometimes 
  the 
  i-arae 
  ap;c 
  specimens 
  were 
  put 
  in 
  all 
  three 
  

   — 
  to 
  liarden, 
  for 
  tlie 
  purpose 
  of 
  cutting 
  sections, 
  and 
  thus 
  

   authenticating 
  the 
  work. 
  The 
  specimens 
  were 
  manipulated 
  

   under 
  the 
  microscope 
  the 
  same 
  as 
  those 
  of 
  the 
  Smelt, 
  page 
  57, 
  

   and 
  the 
  same 
  oculars 
  and 
  objectives 
  used. 
  

  

  Shad 
  eggs 
  are 
  exceedingly 
  adaptable 
  to 
  the 
  use 
  of 
  the 
  em- 
  

   bryologist, 
  on 
  account 
  of 
  their 
  convenient 
  size 
  and 
  great 
  

   transparency. 
  After 
  ''rising" 
  they 
  become 
  about 
  one- 
  

   eight 
  of 
  an 
  inch, 
  more 
  or 
  less, 
  in 
  diameter, 
  and 
  very 
  much 
  

   like 
  round 
  clear 
  crystals. 
  Impregnation 
  seems 
  to 
  take 
  away 
  

   even 
  that 
  opaqueness 
  which 
  existed 
  in 
  the 
  freshly 
  laid 
  egg, 
  

   and 
  what 
  is 
  of 
  much 
  more 
  importance, 
  the 
  vitelline 
  mem- 
  

   brane 
  does 
  not 
  become 
  opac^ue 
  afterwards, 
  so 
  that 
  every 
  pro- 
  

   cess 
  can 
  be 
  seen 
  Avith 
  the 
  greatest 
  distinctness. 
  

  

  Unimpregnated 
  Ovum. 
  

  

  The 
  ovum 
  freshly 
  taken 
  from 
  the 
  Shad 
  consists 
  of 
  a 
  vitel- 
  

   lus, 
  composed 
  of 
  innumerable 
  large 
  and 
  small 
  oil 
  globules, 
  

   embodied 
  in 
  or 
  surrounded 
  by 
  a 
  matrix 
  of 
  granular, 
  some- 
  

   what 
  opaque, 
  plasma, 
  enclosed 
  by 
  a 
  delicate^, 
  nearly 
  hyaline, 
  

   membrane, 
  which 
  at 
  lirst 
  closely 
  embraces 
  the 
  vitellus, 
  and 
  

   which 
  is 
  folded 
  and 
  wrinkled 
  in 
  all 
  directions. 
  Fig. 
  1, 
  PI. 
  

   VI. 
  In 
  the 
  great 
  majority 
  of 
  the 
  unimpregnated 
  ova, 
  this 
  

   vitelline 
  ^membrane^ 
  remains 
  wrinkled 
  and 
  folded 
  closely 
  

   about 
  the 
  vitellus, 
  and 
  even 
  when 
  placed 
  in 
  water, 
  the 
  ab- 
  

   tforption 
  is 
  so 
  slight 
  that 
  the 
  membrane 
  is 
  barely 
  raised 
  from 
  

   the 
  periphery 
  of 
  the^ 
  vitellus, 
  and 
  very 
  few 
  of 
  the 
  foldings 
  

   become 
  obliterated. 
  In 
  some, 
  the 
  absorption 
  is 
  partial. 
  Fig. 
  

  

  