﻿XX 
  -ON 
  THE 
  DEVELOPMENT 
  OF 
  OSSEOUS 
  FISHES, 
  INCLUDING 
  

   MARINE 
  AND 
  FRESHWATER 
  FORMS. 
  

  

  By 
  John 
  A. 
  Ryder. 
  

  

  I. 
  — 
  Gadus 
  morrhua 
  L. 
  {The 
  God.) 
  

  

  The 
  main 
  features 
  of 
  the 
  development 
  of 
  {his 
  species 
  have 
  been 
  de- 
  

   scribed 
  and 
  illustrated 
  in 
  a 
  previous 
  memoir 
  } 
  by 
  the 
  author, 
  so 
  that 
  it 
  

   will 
  not 
  be 
  necessary 
  to 
  do 
  more 
  than 
  to 
  add 
  observations 
  made 
  since 
  

   the 
  publication 
  of 
  that 
  paper, 
  and 
  otherwise 
  complete 
  the 
  record 
  of 
  the 
  

   early 
  life-history 
  of 
  this 
  important 
  food-fish. 
  

  

  The 
  views 
  of 
  Hoffmann 
  2 
  as 
  to 
  the 
  meaning 
  and 
  sequence 
  of 
  the 
  phe- 
  

   nomena 
  attending 
  the 
  fertilization 
  of 
  fish 
  ova 
  have 
  been 
  disputed 
  since 
  

   the 
  above-cited 
  essay 
  was 
  written, 
  and 
  apparently 
  upon 
  the 
  basis 
  of 
  

   well-determined 
  data. 
  The 
  most 
  recent 
  contribution 
  to 
  this 
  subject 
  is 
  

   by 
  Agassiz 
  and 
  Whitman, 
  3 
  who 
  state, 
  page 
  19, 
  in 
  reference 
  to 
  the 
  de- 
  

   velopment 
  of 
  Ctenolabrus, 
  that 
  "immediately 
  after 
  the 
  penetration 
  of 
  

   the 
  spermatozoon 
  a 
  disk-like 
  thickening 
  of 
  the 
  cortical 
  layer 
  appears 
  

   at 
  the 
  lower 
  pole 
  of 
  the 
  egg 
  ; 
  and 
  at 
  the 
  center 
  of 
  this 
  disk 
  may 
  be 
  

   seen, 
  in 
  mounted 
  preparations, 
  the 
  minute 
  male 
  pronucleus. 
  It 
  is 
  a 
  

   curious 
  fact, 
  of 
  which 
  the 
  proof 
  will 
  be 
  given 
  in 
  our 
  second 
  memoir, 
  

   that 
  the 
  male 
  pronucleus 
  becomes 
  the 
  center 
  of 
  attraction 
  around 
  which 
  

   the 
  discoidal 
  aggregation 
  of 
  protoplasm 
  takes 
  place, 
  and 
  towards 
  which, 
  

   after 
  the 
  formation 
  of 
  the 
  second 
  polar 
  globule, 
  the 
  female 
  pronucleus 
  

   gravitates." 
  

  

  In 
  another 
  paper 
  4 
  Agassiz 
  and 
  Whitman 
  have 
  also 
  discussed 
  the 
  

   origin 
  of 
  the 
  periblast, 
  as 
  it 
  is 
  called 
  by 
  them, 
  reaching 
  the 
  conclusion 
  

   that 
  the 
  "autoplasts" 
  (Laukester), 
  the 
  free 
  nuclei 
  of 
  authors, 
  do 
  not 
  

   arise 
  spontaneously 
  in 
  the 
  layer 
  of 
  protoplasm 
  underlying 
  the 
  germinal 
  

   disk, 
  nor 
  from 
  a 
  single 
  nucleus 
  developed 
  at 
  the 
  time 
  of 
  the 
  first 
  cleav- 
  

  

  1 
  A 
  contribution 
  to 
  the 
  embryograjjhy 
  of 
  osseous 
  fishes, 
  with 
  special 
  reference 
  to 
  the 
  

   development 
  of 
  the 
  cod 
  ( 
  Gadus 
  morrhua). 
  Report 
  of 
  the 
  United 
  States 
  Commissioner 
  

   of 
  Fish 
  and 
  Fisheries, 
  part 
  x, 
  for 
  1882, 
  pp. 
  455-605, 
  pis. 
  xii. 
  Washington, 
  1884. 
  

  

  2 
  C.K. 
  Hoffmann. 
  Zur 
  Ontogenie 
  der 
  Knochenfische, 
  chapters 
  i-viii, 
  4to. 
  Amster- 
  

   dam, 
  1881. 
  

  

  3 
  A. 
  Agassiz 
  and 
  C. 
  O. 
  Whitman. 
  The 
  development 
  of 
  osseous 
  fishes. 
  I. 
  The 
  pe- 
  

   lagic 
  stages 
  of 
  young 
  fishes. 
  Studies 
  from 
  the 
  Newport 
  laboratory. 
  Mem. 
  Mus. 
  Comp. 
  

   Zool., 
  xiv, 
  No. 
  1, 
  part 
  1, 
  4to, 
  pp. 
  56, 
  19 
  plates. 
  Cambridge, 
  1885. 
  

  

  4 
  On 
  the 
  development 
  of 
  some 
  pelagic 
  fish 
  eggs, 
  preliminary 
  notice. 
  Proc. 
  Am. 
  Acad. 
  

   Arts 
  and 
  Sciences, 
  xx, 
  8vo, 
  pp. 
  23-75, 
  1 
  pi. 
  1884. 
  

  

  D] 
  489 
  

  

  