﻿388 
  fi- 
  T. 
  Young, 
  

  

  related 
  to 
  the 
  development 
  and 
  later 
  degeneration 
  of 
  the 
  skeins 
  as 
  

   has 
  been 
  suggested 
  by 
  Child 
  (1907, 
  I), 
  Goldschmidt 
  (1905), 
  etc., 
  is 
  

   impossible 
  to 
  say. 
  Nothing 
  resembling 
  a 
  yolk 
  nucleus, 
  such 
  as 
  is 
  

   described 
  by 
  Child 
  (1. 
  c.) 
  or 
  Eichards 
  (1911)^) 
  has, 
  been 
  obser 
  

   ved 
  by 
  me.^) 
  

  

  Formation 
  of 
  ova 
  occurs 
  only 
  in 
  the 
  follicles, 
  where 
  these 
  join 
  

   the 
  oviduct 
  branches 
  the 
  nuclei 
  cease 
  to 
  enlarge, 
  and 
  retain 
  the 
  

   character 
  of 
  typical 
  parenchyma 
  nuclei, 
  while 
  the 
  cords 
  retain 
  their 
  

   syncitial 
  character 
  in 
  this 
  region. 
  The 
  development 
  of 
  these 
  branches 
  

   has 
  already 
  been 
  described. 
  

  

  In 
  Moniezia 
  Child 
  (1907, 
  I) 
  has 
  described 
  the 
  predominant 
  role 
  

   of 
  amitosis 
  in 
  the 
  development 
  of 
  the 
  ovary, 
  and 
  according 
  to 
  

   OouGH 
  (1909) 
  cellular 
  increase 
  in 
  the 
  early 
  ovary 
  of 
  Stilesia 
  centri- 
  

   pundata 
  is 
  amitotic, 
  being 
  succeeded 
  by 
  mitosis 
  iu 
  later 
  stages. 
  Child 
  

   however 
  has 
  found 
  occasional 
  mitoses 
  here, 
  while 
  Richards 
  (1911, 
  

   p. 
  140) 
  finds 
  them 
  "throughout 
  the 
  development 
  of 
  the 
  female 
  germ 
  

   cells 
  in 
  considerable 
  numbers", 
  but 
  states 
  that 
  "They 
  do 
  not 
  occur 
  

   as 
  frequentl}^ 
  as 
  one 
  would 
  a 
  priori 
  expect." 
  In 
  Taenia 
  pisiformis 
  I 
  have 
  

   found 
  no 
  stages 
  of 
  mitosis 
  later 
  than 
  the 
  prophase 
  with 
  one 
  possible 
  

   exception 
  in 
  the 
  early 
  stages 
  of 
  the 
  ovary 
  ■^), 
  but 
  that 
  such 
  may 
  

   occasionally 
  occur 
  I 
  cannot 
  deny. 
  

  

  The 
  yolk 
  gland 
  in 
  its 
  early 
  development 
  is 
  indistinguishable 
  

   from 
  the 
  ovary 
  and 
  the 
  membrane 
  of 
  its 
  follicles 
  has 
  the 
  same 
  

   history 
  as 
  has 
  that 
  of 
  the 
  ovarian 
  follicles. 
  Like 
  the 
  latter 
  it 
  

   arises 
  as 
  a 
  network 
  of 
  cell 
  cords 
  whose 
  basal 
  ends 
  give 
  rise 
  to 
  the 
  

   branches 
  of 
  the 
  yolk 
  duct 
  as 
  described 
  above 
  and 
  whose 
  tips 
  enlarge 
  

   to 
  form 
  the 
  follicles. 
  The 
  yolk 
  cells 
  arise 
  as 
  do 
  the 
  ova 
  from 
  

   specialized 
  parenchyma 
  cells, 
  which 
  appear 
  later 
  to 
  share 
  in 
  the 
  

   formation 
  of 
  the 
  follicular 
  membrane. 
  The 
  early 
  development 
  of 
  

   the 
  yolk 
  cells 
  is 
  similar 
  to 
  that 
  of 
  the 
  ova. 
  Their 
  later 
  development 
  

  

  1) 
  The 
  yolk 
  nuclei 
  shown 
  in 
  Richards' 
  figures 
  are 
  somewhat 
  sug- 
  

   gestive 
  of 
  centrosomes. 
  These 
  however 
  as 
  I 
  hope 
  to 
  show 
  later, 
  are 
  ap- 
  

   parently 
  absent 
  in 
  Taeiiia 
  pisiformis. 
  It 
  is 
  not 
  impossible 
  however 
  that 
  

   Richards' 
  "yolk 
  nucleus" 
  is 
  a 
  yolk 
  granule 
  , 
  lying 
  by 
  chance 
  at 
  the 
  

   center 
  of 
  an 
  attraction 
  sphere. 
  

  

  2) 
  In 
  some 
  cases 
  I 
  find 
  a 
  more 
  homogeneous 
  area 
  in 
  the 
  cytoplasm 
  

   which 
  may 
  possibly 
  correspond 
  with 
  this 
  structure 
  (Fig. 
  55), 
  The 
  fact 
  

   however 
  that 
  it 
  somewhat 
  resembles 
  a 
  faintly 
  stained 
  yolk 
  mass, 
  that 
  

   similar 
  areas 
  are 
  occasionally 
  present 
  in 
  later 
  stages, 
  and 
  its 
  apparently 
  

   inconstant 
  occurrence, 
  render 
  its 
  interpretation 
  very 
  uncertain. 
  

  

  3) 
  In 
  1800 
  cells 
  counted. 
  The 
  number 
  studied 
  is 
  much 
  greater. 
  

  

  