﻿532 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  [44] 
  

  

  The 
  gill-clefts 
  remain 
  uncovered 
  for 
  a 
  long 
  time, 
  as 
  shown 
  in 
  figs. 
  

   150, 
  151, 
  and 
  153, 
  but 
  by 
  tbe 
  twenty-first 
  to 
  the 
  twenty-eighth 
  day 
  the 
  

   opercular 
  folds 
  have 
  grown 
  to 
  such 
  an 
  extent 
  that 
  the 
  clefts 
  and 
  gills 
  

   are 
  quite 
  concealed 
  from 
  observation 
  externally. 
  When 
  the 
  fish 
  reaches 
  

   that 
  stage 
  of 
  development 
  it 
  measures 
  22 
  mm 
  in 
  length, 
  or 
  not 
  far 
  from 
  

   an 
  inch, 
  and 
  has 
  a 
  heterocercal 
  tail 
  in 
  which 
  the 
  permanent 
  rays 
  are 
  

   well 
  developed, 
  as 
  they 
  are 
  in 
  all 
  of 
  the 
  fins 
  except 
  the 
  ventrals. 
  The 
  

   first 
  obvious 
  intimation 
  of 
  heterocercal 
  ity 
  in 
  the 
  larval 
  shad 
  appears 
  on 
  

   the 
  seventeenth 
  day, 
  as 
  shown 
  in 
  fig. 
  150, 
  representing 
  a 
  rather 
  stunted 
  

   larva 
  measuring 
  14 
  mm 
  in 
  length. 
  The 
  fopd 
  during 
  the 
  later 
  larval 
  stages 
  

   does 
  not 
  accumulate 
  in 
  the 
  stomach, 
  but 
  accumulates 
  in 
  the 
  intestine 
  J, 
  

   just 
  behind 
  the 
  pylorus, 
  as 
  shown 
  in 
  fig. 
  150. 
  It 
  is 
  only 
  after 
  the 
  young 
  

   fish 
  acquires 
  mobility 
  of 
  its 
  jaws 
  that 
  it 
  begins 
  to 
  feed, 
  and 
  after 
  the 
  

   small 
  teeth 
  already 
  mentioned 
  have 
  appeared; 
  indeed, 
  the 
  larvae 
  about 
  

   this 
  time 
  occasionally 
  become 
  so 
  ravenous 
  that 
  they 
  have 
  been 
  known 
  

   to 
  attempt 
  to 
  eat 
  each 
  other, 
  and 
  finally 
  strangle 
  in 
  their 
  efforts 
  at 
  con- 
  

   summating 
  cannibalism. 
  

  

  The 
  temperature 
  at 
  which 
  the 
  ova 
  of 
  the 
  shad 
  develop 
  normally 
  ranges 
  

   from 
  about 
  55°, 
  or 
  perhaps 
  slightly 
  less, 
  up 
  to 
  about 
  80° 
  Fahr. 
  Experi- 
  

   ments 
  made 
  to 
  determine 
  the 
  lowest 
  temperature 
  at 
  which 
  normal 
  de- 
  

   velopment 
  would 
  take 
  place 
  gave 
  some 
  very 
  interesting 
  results. 
  It 
  was 
  

   found 
  that 
  at 
  a 
  little 
  below 
  52° 
  Fahr. 
  abnormalities 
  of 
  various 
  kinds 
  were 
  

   sure 
  to 
  appear. 
  Some 
  of 
  these 
  I 
  have 
  figured 
  from 
  micro-photographs 
  

   on 
  plate 
  xviii. 
  Figs. 
  122 
  and 
  123 
  show 
  how 
  the 
  development 
  of 
  the 
  

   tail 
  and 
  notochord 
  was 
  impaired 
  when 
  the 
  embryos 
  were 
  subjected 
  to 
  a 
  

   temperature 
  ranging 
  from 
  45° 
  to 
  48° 
  Fahr. 
  Fig. 
  124 
  shows 
  how 
  the 
  

   development 
  of 
  the 
  blastodisk 
  became 
  impaired 
  when 
  subjected 
  to 
  the 
  

   same 
  low 
  temperature. 
  

  

  A 
  great 
  variation 
  in 
  the 
  period 
  of 
  hatching 
  of 
  this 
  species 
  is 
  caused 
  

   by 
  variations 
  in 
  the 
  temperature 
  of 
  the 
  water 
  during 
  the 
  hatching 
  sea- 
  

   son; 
  for 
  example, 
  at. 
  74° 
  Fahr. 
  hatching 
  occurs 
  in 
  about 
  seventy 
  hours 
  ; 
  

   at 
  04.5° 
  Fahr. 
  in 
  one 
  hundred 
  and 
  nine 
  hours 
  ; 
  at 
  57.2° 
  Fahr. 
  in 
  one 
  hun- 
  

   dred 
  and 
  forty-eight 
  hours 
  or 
  over 
  six 
  days. 
  1 
  have 
  known 
  it 
  to 
  require 
  

   seventeen 
  davs 
  for 
  the 
  ova 
  of 
  the 
  shad 
  to 
  hatch 
  when 
  the 
  average 
  tem- 
  

   perature 
  of 
  the 
  water 
  was 
  53.75° 
  Fahr. 
  In 
  ordinary 
  pleasant 
  spring 
  

   weather 
  the 
  eggs 
  usually 
  hatch 
  during 
  the 
  third 
  or 
  fourth 
  day 
  after 
  

   fertilization. 
  

  

  The 
  first 
  paper 
  of 
  note 
  on 
  the 
  development 
  of 
  the 
  shad 
  was 
  published 
  

   by 
  the 
  late 
  Prof. 
  H. 
  J. 
  Rice 
  46 
  in 
  1878. 
  Since 
  then 
  the 
  writer 
  has 
  pub- 
  

   lished 
  additional 
  observations 
  47 
  on 
  the 
  development 
  and 
  the 
  retardation 
  

   of 
  the 
  development 
  of 
  the 
  eggs 
  and 
  on 
  the 
  feeding 
  48 
  of 
  this 
  species. 
  

  

  46 
  H. 
  J. 
  Rice. 
  Notes 
  upon 
  the 
  development 
  of 
  tbe 
  shad 
  (Alosa 
  sapidissima 
  ?). 
  Re- 
  

   port 
  of 
  a 
  Commissioner 
  of 
  Fisheries 
  of 
  Maryland, 
  January, 
  1878, 
  pp. 
  95-106, 
  pi. 
  vi. 
  

  

  47 
  J. 
  A. 
  Ryder. 
  On 
  the 
  retardation 
  of 
  the 
  development 
  of 
  the 
  ova 
  of 
  the 
  shad. 
  

   Bull. 
  U. 
  S. 
  Fish 
  Com., 
  i, 
  1881, 
  pp. 
  177-190 
  and 
  422-424. 
  

  

  48 
  J. 
  A. 
  Ryder. 
  Observations 
  on 
  tbe 
  absorption 
  of 
  the 
  yelk, 
  the 
  food, 
  feeding, 
  and 
  

   development 
  of 
  embryo 
  fishes. 
  Bull. 
  U. 
  S. 
  Fish 
  Com., 
  ii, 
  1882, 
  pp. 
  179-205. 
  One 
  fig- 
  

   ure 
  in 
  text. 
  

  

  