﻿574 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  [86] 
  

  

  EXPLANATION 
  OF 
  PLATE 
  XV. 
  

   Clupea 
  sapidissima. 
  ( 
  The 
  Common 
  Shad. 
  ) 
  

  

  Fig. 
  93. 
  Section 
  through 
  the 
  hlastodisk 
  of 
  an 
  egg 
  at 
  a 
  stage 
  intermediate 
  between 
  

   those 
  represented 
  in 
  figs. 
  91 
  and 
  92. 
  

  

  Fig. 
  94. 
  A 
  section 
  of 
  the 
  germinal 
  pole, 
  same 
  egg, 
  near 
  the 
  edge 
  of 
  the 
  blastodisk, 
  

   showing 
  the 
  thick 
  layer 
  of 
  periblast 
  just 
  under 
  its 
  margin. 
  

  

  Fig. 
  95. 
  Section 
  through 
  a 
  blastodisk 
  somewhat 
  older 
  than 
  that 
  shown 
  in 
  fig. 
  92, 
  

   showing 
  the 
  epidermal 
  layer 
  differentiated 
  and 
  with 
  large 
  nuclei 
  at 
  one 
  side 
  

   embedded 
  in 
  the 
  periblast. 
  

  

  Fig. 
  96. 
  Sagittal 
  section 
  through 
  a 
  more 
  advanced 
  stage, 
  showing 
  the 
  cleavage 
  cavity 
  

   sc 
  beneath 
  the 
  central 
  portion 
  of 
  the 
  epiblast 
  e, 
  and 
  the 
  inflected 
  hypoblastic 
  

   layer 
  h 
  just 
  within 
  the 
  lips 
  oo 
  of 
  the 
  blastopore. 
  

  

  Fig. 
  97. 
  Portion 
  of 
  a 
  longitudinal 
  vertical 
  section 
  of 
  the 
  side 
  of 
  the 
  body 
  of 
  an 
  embryo 
  

   at 
  the 
  stage 
  represented 
  in 
  fig. 
  98, 
  to 
  show 
  that 
  the 
  solid 
  myotomes 
  MM 
  M 
  are 
  

   more 
  intimately 
  united 
  to 
  the 
  hypoblast 
  h 
  than 
  to 
  the 
  epiblast 
  e. 
  Very 
  much 
  en- 
  

   larged. 
  

  

  FlG. 
  98. 
  Semidiagramuiatic 
  longitudinal 
  median 
  section 
  through 
  an 
  embryo 
  after 
  

   the 
  blastopore 
  has 
  closed, 
  to 
  show 
  the 
  position 
  of 
  the 
  first 
  myotomes 
  and 
  the 
  con- 
  

   tinuity 
  of 
  the 
  chorda 
  ch 
  posteriorly 
  with 
  the 
  lower 
  or 
  hypoblastic 
  layer; 
  sc, 
  cleav- 
  

   age 
  cavity. 
  

  

  Fig. 
  99. 
  Median 
  longitudinal 
  section 
  through 
  the 
  head 
  of 
  a 
  more 
  advanced 
  embryo, 
  

   through 
  the 
  nasal 
  pit, 
  eye, 
  gill-arches, 
  brain, 
  and 
  chorda, 
  and 
  showing 
  the 
  rela- 
  

   tions 
  of 
  the 
  periblast 
  p. 
  

  

  Fig. 
  100. 
  A 
  similar 
  section 
  of 
  the 
  same 
  stage 
  somewhat 
  off 
  of 
  the 
  median 
  line. 
  The 
  

   auditory 
  capsule 
  au 
  is 
  cut 
  through, 
  also 
  the 
  gill-arches, 
  the 
  heart 
  h, 
  and 
  the 
  oral 
  

   cavity 
  b 
  above 
  the 
  latter. 
  

  

  