﻿386 
  R. 
  T. 
  Young, 
  

  

  varying 
  size. 
  These 
  granules 
  soon 
  unite 
  to 
  form 
  a 
  long 
  twisted 
  

   skein, 
  representing 
  the 
  close 
  skein 
  of 
  an 
  ordinary 
  mitosis. 
  It 
  is 
  

   not 
  truly 
  close 
  however 
  the 
  loops 
  being 
  discontinuous. 
  The 
  close 
  

   skein 
  soon 
  contracts 
  to 
  form 
  a 
  loose 
  skein, 
  breaking 
  up 
  into 
  a 
  

   number 
  of 
  irregular 
  loops 
  and 
  rods 
  (Figs. 
  52 
  and 
  56). 
  

  

  In 
  Moniesia 
  Richards 
  (1911) 
  finds 
  evidence 
  of 
  a 
  synapsis 
  at 
  

   this 
  stage, 
  but 
  I 
  have 
  seen 
  no 
  signs 
  of 
  such 
  a 
  process 
  in 
  my 
  material. 
  

   The 
  "nucleolus" 
  apparently 
  contributes 
  to 
  the 
  skeins 
  as 
  it 
  is 
  in 
  

   intimate 
  connection 
  with 
  these 
  at 
  an 
  early 
  stage 
  and 
  disappears 
  

   during 
  their 
  growth 
  (Fig. 
  56). 
  Such 
  a 
  condition 
  has 
  been 
  described 
  

   by 
  Child 
  (1907, 
  I) 
  in 
  Moniesia 
  and 
  is 
  additional 
  evidence 
  of 
  its 
  

   chromatic 
  nature.^) 
  

  

  No 
  further 
  mitotic 
  stages 
  occur 
  at 
  this 
  time 
  "^) 
  , 
  the 
  skeins 
  

   breaking 
  up 
  to 
  form 
  the 
  reticulum 
  of 
  the 
  oocyte 
  nucleus 
  and 
  an 
  

   incomplete 
  nuclear 
  membrane 
  forming 
  apparently 
  fiora 
  the 
  latter 
  

   (Fig. 
  32). 
  During 
  the 
  reconstitution 
  of 
  the 
  oocyte 
  nucleus 
  a 
  distinct 
  

   "nucleolus" 
  may 
  form, 
  apparently 
  from 
  the 
  chromatin 
  network, 
  or 
  

   it 
  may 
  occasionally 
  be 
  absent, 
  being 
  replaced 
  by 
  the 
  smaller 
  chro- 
  

   matin 
  bodies 
  in 
  the 
  network. 
  A 
  true 
  nucleolus 
  is 
  apparently 
  absent.^) 
  

   We 
  here 
  find 
  a 
  closely 
  analogous 
  process 
  to 
  that 
  occurring 
  after 
  

   the 
  spermatogonia! 
  divisions 
  in 
  spermatogenesis^), 
  and 
  adopting 
  a 
  

   terminology 
  similar 
  to 
  that 
  employed 
  there 
  the 
  cells 
  undergoing 
  

   this 
  abortive 
  mitosis 
  must 
  be 
  called 
  primary 
  oocytes, 
  even 
  tho 
  the 
  

   growth 
  period 
  is 
  coincident 
  therewith, 
  rather 
  than 
  precedent 
  thereto. 
  

  

  The 
  formation 
  of 
  distinct 
  skeins 
  has 
  been 
  described 
  by 
  

   V. 
  Janicki 
  (1907) 
  in 
  Taenia 
  serrata, 
  but 
  he 
  calls 
  attention 
  to 
  

   the 
  absence 
  of 
  later 
  mitotic 
  stages. 
  Skein 
  degeneration 
  has 
  been 
  

   noted 
  by 
  Wheelek 
  (1894) 
  in 
  Planocera 
  inqmlina, 
  Child 
  (1907, 
  I), 
  

   and 
  Richard's 
  (1911) 
  in 
  Moniezia, 
  v. 
  Janicki 
  (1907) 
  in 
  Taenia 
  serrata 
  

   etc., 
  but 
  no 
  satisfactory 
  explanation 
  of 
  this 
  phenomenon 
  has 
  yet 
  

   been 
  given. 
  According 
  to 
  the 
  figures 
  of 
  Richards 
  (1. 
  c.) 
  this 
  abortive 
  

   mitosis 
  does 
  not 
  proceed 
  as 
  far 
  in 
  Moniezia 
  as 
  in 
  Taenia, 
  the 
  skeins 
  

   remaining 
  in 
  a 
  granular 
  condition 
  and 
  not 
  passing 
  into 
  the 
  loose 
  

   stage 
  described 
  and 
  photographed 
  by 
  me. 
  He 
  does 
  not 
  discuss 
  it 
  

  

  1) 
  See 
  Young 
  (1910, 
  p. 
  146, 
  148—150) 
  and 
  below, 
  page 
  406. 
  

  

  2) 
  I 
  have 
  seen 
  one 
  probable 
  metaphase. 
  

  

  3) 
  See 
  page 
  406. 
  

  

  4) 
  See 
  page 
  377. 
  It 
  is 
  to 
  be 
  noted 
  however 
  that 
  in 
  the 
  latter 
  the 
  

   primary 
  spermatocytes 
  break 
  down 
  and 
  do 
  not 
  form 
  the 
  secondary 
  sper- 
  

   matocytes 
  directly. 
  

  

  