﻿n 
  

  

  ed 
  by 
  the 
  vitelline 
  meiiiLrane 
  witliiii 
  the 
  egg. 
  It 
  now, 
  how- 
  

   ever, 
  at 
  about 
  this 
  stage 
  of 
  development, 
  becomes 
  free 
  from 
  

   the 
  egg, 
  and 
  swims 
  freely 
  about 
  in 
  the 
  water, 
  looking 
  to 
  the 
  

   naked 
  eye 
  very 
  much 
  like. 
  an 
  animated 
  bit 
  of 
  isin-glass 
  

   with 
  tu'o 
  bhick 
  dots 
  at 
  the 
  end. 
  At 
  this 
  time 
  it 
  is 
  some- 
  

   what 
  less 
  than 
  tliroe-eighths 
  of 
  an 
  inch 
  in 
  length, 
  and 
  being 
  

   very 
  transparent, 
  could 
  hardly 
  bo 
  seen 
  in 
  the 
  water, 
  were 
  it 
  

   not 
  for 
  the 
  comparatively 
  large 
  black 
  eyes. 
  Side 
  and 
  top 
  

   views 
  of 
  the 
  young 
  Smelt 
  at 
  this 
  stage, 
  but 
  very 
  much 
  en- 
  

   larged, 
  are 
  given 
  in 
  Figs. 
  1 
  and 
  2, 
  PI. 
  V. 
  Most 
  of 
  the 
  

   structures 
  and 
  organs 
  already 
  mentioned 
  can 
  be 
  readily 
  seen; 
  

   the 
  intestine 
  passing 
  along 
  the 
  centre 
  of 
  the 
  body 
  beneath 
  

   the 
  notochord 
  and 
  above 
  the 
  yolk 
  mass, 
  from 
  mouth 
  to 
  anus 
  ; 
  

   the 
  heart 
  with 
  its 
  posterior 
  and 
  anterior 
  attachments, 
  now 
  

   not 
  only 
  divided 
  into 
  two 
  distinct 
  portions, 
  but 
  relatively 
  

   much 
  smaller 
  than 
  heretofore, 
  and 
  the 
  auricle 
  crowded 
  for- 
  

   ward 
  upon 
  the 
  ventricle 
  ; 
  the 
  ear 
  with 
  its 
  forming 
  semi-cir- 
  

   cular 
  canals 
  ; 
  the 
  nasal 
  sack 
  somewhat 
  closed 
  ; 
  the 
  promi- 
  

   nent 
  pigmented 
  eyes 
  ; 
  the 
  much 
  enlarged 
  pectoral 
  tins 
  ; 
  the 
  

   yolk 
  mass, 
  now 
  much 
  absorbed 
  in 
  nourishing 
  the 
  body, 
  and 
  

   gradually 
  becoming 
  enclosed 
  by 
  the 
  body 
  walls 
  ; 
  and 
  the 
  

   quite 
  advanced 
  brain. 
  The 
  further 
  stages 
  of 
  the 
  brain 
  may 
  

   be 
  seen 
  by 
  consulting 
  Figs. 
  10, 
  14 
  and 
  15, 
  PI. 
  V. 
  In 
  Figs. 
  

   10 
  and 
  15, 
  PI. 
  V, 
  the 
  brain 
  presents 
  the 
  same 
  general 
  fea- 
  

   tures 
  as 
  in 
  Fig. 
  '2, 
  PI. 
  Y, 
  with 
  the 
  exception 
  that 
  all 
  the 
  

   divisions 
  are 
  more 
  strongly 
  marked. 
  

  

  The 
  posterior 
  lobes 
  are 
  gradually 
  approaching 
  each 
  other 
  

   to 
  unite 
  on 
  the 
  median 
  line 
  dorsally, 
  and 
  form 
  the 
  cerebel- 
  

   lum, 
  while 
  the 
  prominent 
  portions 
  immediately 
  in 
  front 
  of 
  

   the 
  cerebellic 
  divisions 
  are 
  thickening 
  and 
  rounding 
  out 
  to 
  

   become 
  the 
  optic 
  lobes, 
  and 
  the 
  anterior 
  part 
  is 
  also 
  chang- 
  

   ing 
  form 
  to 
  finally 
  assume 
  the 
  shape 
  of 
  the 
  cerebral 
  and 
  

   olfactory 
  lobes. 
  In 
  Fig. 
  14, 
  PI. 
  V, 
  these 
  parts 
  are 
  represeut- 
  

   e:l 
  as 
  seen 
  in 
  the 
  adult 
  fish 
  and 
  of 
  natural 
  size. 
  The 
  brain, 
  

   as 
  thus 
  seen 
  from 
  above, 
  forms 
  what 
  the 
  fishermen 
  call 
  the 
  

   ''old 
  man's 
  face," 
  seen 
  in 
  the 
  adult 
  Smelt, 
  through 
  the 
  

  

  