﻿578 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  [90] 
  

  

  EXPLANATION 
  OF 
  PLATE 
  XVII. 
  

  

  i 
  

  

  Clupea 
  sapidissima. 
  (The 
  Common 
  Shad.) 
  

  

  Figs. 
  114, 
  115, 
  116, 
  and 
  117. 
  Four 
  views 
  of 
  successive 
  stages 
  of 
  the 
  development 
  of 
  

   the 
  head 
  and 
  optic 
  lobes 
  of 
  the 
  embryo 
  shad, 
  commencing 
  with 
  the 
  stage 
  when 
  

   the 
  front 
  end 
  of 
  the 
  head 
  of 
  the 
  embryo 
  is 
  visibly 
  differentiated 
  when 
  viewed 
  as 
  

   a 
  transparent 
  object 
  with 
  transmitted 
  light. 
  

  

  Fig. 
  118. 
  Section 
  through 
  the 
  spreading 
  blastoderm 
  of 
  the 
  shad 
  at 
  a 
  somewhat 
  earlier 
  

   stage 
  than 
  that 
  shown 
  in 
  fig. 
  96 
  ; 
  h, 
  hypoblast; 
  e, 
  epiblast 
  ; 
  sc, 
  segmentation 
  cav- 
  

   ity 
  ; 
  o 
  o, 
  lips 
  of 
  the 
  blastopore. 
  

  

  Fig. 
  119. 
  Diagrammatic 
  sagittal 
  section 
  through 
  the 
  embryonic 
  axis 
  eof 
  a 
  shad 
  egg, 
  

   the 
  blastoderm 
  of 
  which 
  has 
  enveloped 
  one-half 
  of 
  the 
  vitellus. 
  The 
  jagged 
  line 
  

   represents 
  the 
  lateral 
  limit 
  of 
  the 
  cleavage 
  cavity 
  sc. 
  

  

  Fig. 
  120. 
  Egg 
  of 
  the 
  shad 
  in 
  which 
  the 
  blastopore 
  has 
  just 
  closed. 
  Only 
  four 
  myo- 
  

   tomes 
  have 
  been 
  developed 
  in 
  the 
  mid-region 
  of 
  the 
  embryonic 
  axis. 
  

  

  Fig. 
  121. 
  Cross-section 
  through 
  the 
  body 
  and 
  yelk-sack 
  of 
  a 
  young 
  shad 
  in 
  about 
  the 
  

   conditiou 
  of 
  development 
  represented 
  in 
  fig. 
  127; 
  ch, 
  the 
  thick 
  chorda; 
  i, 
  intes- 
  

   tine; 
  be, 
  body 
  cavity; 
  p, 
  periblast 
  or 
  splanchnopleure 
  investing 
  the 
  yelky 
  ; 
  sc, 
  

   cleavage 
  cavity 
  ; 
  e, 
  thin 
  outer 
  epiblastic 
  investment 
  of 
  the 
  yelk. 
  

  

  S. 
  Mis. 
  70 
  37 
  

  

  