﻿/ntroductory 
  Note 
  to 
  Mr. 
  Winslow's 
  Paper. 
  

  

  [This 
  paper 
  is 
  a. 
  desirable 
  contribution 
  to 
  the 
  literature 
  

   of 
  embryology, 
  inasmuch 
  as 
  the 
  observer 
  has 
  been 
  able 
  

   to 
  follow 
  the 
  development 
  of 
  Ostrea 
  eduUs 
  from 
  its 
  ear- 
  

   liest 
  i^hases, 
  which 
  has 
  never 
  been 
  done 
  before 
  by 
  any 
  

   embryologist, 
  although 
  the 
  artificial 
  impregnation 
  of 
  the 
  

   eggs 
  was 
  attempted 
  by 
  M. 
  Davaine, 
  who 
  says 
  he 
  failed, 
  

   and 
  that 
  the 
  eggs 
  soon 
  became 
  putrid 
  and 
  the 
  water 
  con- 
  

   taining 
  them 
  swarmed 
  with 
  infusoria. 
  M. 
  Davaine' 
  s 
  

   figures 
  bear 
  the 
  marks 
  of 
  having 
  been 
  carefully 
  made 
  

   from 
  close 
  observations, 
  but 
  he 
  ol)tained 
  his 
  material 
  

   from 
  the 
  upper 
  gill 
  chamber, 
  where 
  the 
  ova 
  had 
  already 
  

   undergcme 
  all 
  the 
  changes 
  rei:>resented 
  from 
  Figs. 
  1 
  to 
  16 
  

   of 
  Brook's 
  drawings 
  of 
  the 
  early 
  stages 
  of 
  the 
  American 
  

   species. 
  Many 
  things 
  have 
  accordingly 
  escaped 
  the 
  

   notice 
  of 
  the 
  French 
  author, 
  who 
  did 
  not 
  see 
  the 
  "polar 
  

   globules 
  f 
  the 
  tirst 
  and 
  second 
  periods 
  of 
  rest 
  and 
  activity 
  

   at 
  all. 
  He 
  also 
  failed 
  to 
  recognize 
  in 
  the 
  embryos 
  with 
  

   the 
  dorsal 
  saddle-like 
  depression, 
  a 
  blastopore 
  stage 
  and 
  

   the 
  epibolic 
  invagination 
  of 
  the 
  hypoblast. 
  He, 
  however, 
  

   finds 
  tliat 
  the 
  shell 
  originates 
  in 
  the 
  position 
  of 
  the 
  blas- 
  

   topore, 
  as 
  shown 
  by 
  Brooks. 
  He 
  states 
  that 
  the 
  velum 
  

   atrophies 
  Avith 
  the 
  development 
  of 
  the 
  mantle 
  and 
  gills; 
  

   but 
  does 
  not 
  describe 
  the 
  latter. 
  He 
  does 
  not 
  note 
  the 
  

   presence 
  of 
  a 
  membrane 
  around 
  the 
  ovarian 
  egg, 
  and 
  it 
  

   seems 
  to 
  me 
  the 
  membrane 
  is 
  a 
  continuation 
  of 
  the 
  vitel- 
  

   line, 
  which 
  forms 
  a 
  stalk 
  by 
  which 
  the 
  ovum 
  is 
  attached 
  

   to 
  the 
  walls 
  of 
  the 
  follicles 
  of 
  the 
  ovary, 
  making 
  a 
  chan- 
  

   nel 
  for 
  the 
  pa 
  ssage 
  of 
  ])lasma 
  for 
  the 
  growth 
  of 
  the 
  ovum, 
  

   as 
  suggested 
  by 
  Balfour. 
  

  

  