﻿49 
  

  

  came 
  a 
  cold 
  spell. 
  The 
  air 
  thermometer 
  indicated 
  a 
  decrease 
  

   of, 
  at 
  its 
  utmost, 
  eighteen 
  degrees 
  (18°); 
  the 
  temperature 
  of 
  

   the 
  river 
  sank 
  at 
  same 
  time 
  about 
  12°; 
  and 
  the 
  hydrant 
  

   water 
  received 
  a 
  sudden 
  cold 
  to 
  the 
  extent 
  of 
  about 
  three 
  

   degrees. 
  Up 
  to 
  the 
  end 
  of 
  this 
  cold 
  period, 
  there 
  was 
  barely 
  

   a 
  sign 
  of 
  development 
  in 
  those 
  eggs 
  which 
  were 
  not 
  certainly 
  

   dead, 
  and 
  it 
  was 
  questionable 
  what 
  the 
  result 
  would 
  be 
  with 
  

   the 
  eggs 
  which 
  appeared 
  to 
  be 
  living. 
  But 
  with 
  the 
  storm 
  

   and 
  freshet, 
  the 
  cold 
  weather 
  appeared 
  to 
  pass 
  away. 
  The 
  

   temperature 
  of 
  the 
  hydrant 
  water 
  rose 
  steadily, 
  and 
  in 
  a 
  

   week's 
  time 
  had 
  risen 
  four 
  or 
  five 
  degrees 
  ; 
  and 
  of 
  course 
  

   the 
  rise 
  in 
  the 
  air 
  and 
  liver 
  was 
  mucli 
  greater. 
  With 
  this 
  

   rise 
  in 
  temperature 
  a 
  change 
  in 
  the 
  eggs 
  became 
  visible 
  ; 
  the 
  

   development 
  could 
  be 
  made 
  out, 
  and 
  it 
  was 
  very 
  soon 
  evident 
  

   that 
  many 
  of 
  them 
  at 
  least 
  were 
  alive, 
  and 
  seemed 
  in 
  a 
  fair 
  

   way 
  of 
  producing 
  eacli 
  its 
  young 
  smelt. 
  About 
  the 
  26tli 
  or 
  

   27th 
  of 
  March 
  I 
  took 
  some 
  eggs 
  which 
  had 
  been 
  spawned 
  on 
  

   the 
  3d 
  and 
  5th 
  of 
  the 
  same 
  month, 
  and 
  which 
  showed 
  some 
  

   signs 
  of 
  development 
  — 
  in 
  fact 
  the 
  embryo 
  could 
  be 
  made 
  out 
  

   as 
  a 
  mere 
  bar, 
  very 
  nearly 
  alike 
  at 
  both 
  ends, 
  coiled 
  around 
  

   the 
  yolk 
  — 
  and 
  brought 
  them 
  into 
  the 
  room 
  where 
  I 
  was 
  at 
  

   work 
  with 
  the 
  microscope, 
  and 
  where 
  the 
  temperature 
  was 
  

   about 
  70°. 
  I 
  let 
  them 
  remain 
  in 
  the 
  water 
  in 
  which 
  they 
  

   were 
  brought 
  in, 
  and 
  only 
  changed 
  it 
  by 
  adding 
  fresh 
  water 
  

   as 
  the 
  other 
  evaporated 
  . 
  The 
  water 
  which 
  was 
  added 
  was 
  

   such 
  as 
  had 
  been 
  in 
  the 
  room 
  for 
  some 
  time, 
  so 
  that 
  it 
  was 
  of 
  

   considerable 
  higher 
  temperature 
  than 
  that 
  of 
  the 
  hydrant. 
  

   The 
  eggs 
  thus 
  placed 
  in 
  comparatively 
  stale 
  and 
  warm 
  water, 
  

   rapidly 
  developed, 
  and 
  on 
  the 
  Sd 
  of 
  April 
  a 
  few 
  of 
  the 
  young 
  

   fish 
  hatched 
  out, 
  or 
  just 
  one 
  month 
  from 
  the 
  time 
  the 
  spawn 
  

   was 
  taken. 
  In 
  the 
  case 
  of 
  these 
  young 
  fish 
  we 
  ought 
  to 
  deduct 
  

   at 
  least 
  two 
  weeks, 
  since 
  there 
  was 
  hardly 
  any 
  development 
  

   of 
  the 
  embryo 
  until 
  the 
  temperature 
  of 
  the 
  hydrant 
  water 
  

   rose 
  to 
  near 
  40°. 
  I 
  think 
  it 
  can 
  be 
  said, 
  with 
  a 
  considerable 
  

   degree 
  of 
  certainty, 
  that 
  after 
  impregnation, 
  a 
  certain, 
  but 
  

   very 
  small 
  degree 
  of 
  differentiation 
  will 
  take 
  place 
  when 
  the 
  

  

  