﻿390 
  R. 
  T. 
  Young, 
  

  

  and 
  later 
  migrating 
  into 
  the 
  cytoplasm 
  have 
  there 
  gathered 
  about 
  

   itself 
  the 
  cytoplasmic 
  rays 
  to 
  form 
  an 
  aster. 
  

  

  In 
  MonieHa 
  according 
  to 
  Child 
  (1907, 
  III) 
  asters 
  are 
  absent 
  in 
  

   the 
  maturation 
  of 
  the 
  Qgg 
  altho 
  present 
  in 
  spermatogenesis, 
  while 
  

   EicHARDs 
  (1911, 
  p. 
  151, 
  foot-note) 
  states 
  that 
  in 
  the 
  same 
  genus 
  he 
  

   "succeeded 
  in 
  distinguiv^hing 
  faint 
  radiations 
  in 
  numerous 
  maturation 
  

   stages". 
  The 
  latter 
  (1909, 
  p. 
  318) 
  states 
  that 
  in 
  Taenia 
  serrata 
  "While 
  

   spindle 
  formation 
  is 
  quite 
  regular 
  the 
  achromatic 
  fibres 
  do 
  not 
  stain 
  

   well 
  and 
  frequently 
  the 
  entire 
  structure 
  is 
  overlooked". 
  In 
  vaj 
  

   own 
  preparations 
  both 
  asters 
  and 
  spindles 
  are 
  distinctly 
  tho 
  not 
  

   prominently 
  developed 
  (Fig. 
  60 
  et 
  seq.), 
  and 
  v. 
  Janicki 
  (1907) 
  also 
  

   figures 
  them 
  very 
  clearly. 
  In 
  Moniesia 
  Child 
  (1. 
  c, 
  p. 
  139) 
  finds 
  

   the 
  spindle 
  composed 
  of 
  "exceedingly 
  delicate 
  and 
  faintly 
  visible" 
  

   structures 
  and 
  apparently 
  "wholly 
  intranuclear". 
  Regarding 
  the 
  

   spindle 
  origin 
  in 
  Taenia 
  pisiformis 
  I 
  can 
  make 
  no 
  positive 
  state- 
  

   ments, 
  but 
  from 
  the 
  paucity 
  of 
  intranuclear 
  fibres 
  precedent 
  to 
  its 
  

   formation, 
  I 
  believe 
  that 
  it, 
  as 
  well 
  as 
  the 
  asters, 
  arises 
  at 
  least 
  

   mainly 
  outside 
  the 
  nucleus. 
  Child 
  describes 
  and 
  figures 
  "very 
  

   large 
  centrosomes" 
  (1. 
  c.) 
  in 
  which 
  may 
  occur 
  "deeply 
  staining 
  

   granules" 
  or 
  "centrioles", 
  whose 
  occurrence 
  is 
  "seemingly 
  rather 
  

   irregular". 
  Richards 
  (1911, 
  p. 
  151) 
  also 
  mentions 
  "large 
  globular 
  

   centrosomes 
  — 
  ring-shaped 
  in 
  section 
  — 
  " 
  in 
  Moniesia. 
  In 
  my 
  own 
  

   material 
  the 
  area 
  at 
  the 
  center 
  of 
  the 
  aster 
  in 
  no 
  way 
  resembles 
  

   a 
  definite 
  centrosome, 
  while 
  occasional 
  inclusions 
  therein 
  occur 
  

   too 
  irregularly 
  to 
  have 
  any 
  probable 
  structural 
  or 
  functional 
  

   significance. 
  

  

  In 
  the 
  çt^^ 
  above 
  mentioned 
  the 
  nuclear 
  membrane 
  is 
  breaking 
  

   down 
  and 
  the 
  chromatin 
  gathering 
  itself 
  directly, 
  without 
  the 
  inter- 
  

   vention 
  of 
  any 
  skein 
  stage 
  whatever, 
  into 
  irregular 
  masses, 
  the 
  

   anlagen 
  of 
  the 
  chromosomes. 
  If, 
  as 
  I 
  have 
  attempted 
  to 
  show, 
  the 
  

   nuclear 
  membrane 
  is 
  merely 
  the 
  peripheral 
  part 
  of 
  the 
  nuclear 
  

   reticulum, 
  then 
  with 
  its 
  disappearance 
  there 
  occurs 
  a 
  considerable 
  

   loss 
  of 
  chromatin 
  at 
  this 
  stage, 
  which 
  loss 
  is 
  partly 
  at 
  least 
  re- 
  

   placed 
  by 
  that 
  of 
  the 
  male 
  pronucleus. 
  

  

  Neither 
  by 
  Child 
  (1907, 
  HI) 
  nor 
  v. 
  Janicki 
  (1907) 
  is 
  any 
  

   mention 
  made 
  of 
  skeins 
  in 
  this 
  division, 
  the 
  former 
  merely 
  stating 
  

   (1. 
  c, 
  p. 
  139) 
  that 
  "Chromosomes 
  soon 
  begin 
  to 
  form 
  in 
  the 
  nucleus", 
  

   while 
  the 
  latter 
  (1. 
  c, 
  p. 
  174) 
  says 
  "Das 
  Keimbläschen 
  verliert 
  die 
  

   scharf 
  umschriebene 
  Begrenzung, 
  und 
  es 
  findet 
  in 
  ihm 
  die 
  Aus- 
  

   bildung 
  von 
  Chromosomen 
  statt 
  . 
  . 
  . 
  der 
  Kernraum 
  erscheint 
  von 
  

  

  