﻿Reproductive 
  organs 
  of 
  Taenia 
  pisiformis. 
  391 
  

  

  kleinen 
  wenig 
  färbbaren 
  Körnchen 
  erfüllt. 
  Später 
  schreitet 
  die 
  Auf- 
  

   lösung 
  des 
  homogenen 
  durchsichtigen 
  Kernraums 
  unter 
  Ausbildung 
  

   von 
  Chromosomen 
  fort 
  . 
  . 
  ." 
  

  

  The 
  next 
  stage 
  in 
  development 
  finds 
  the 
  nuclear 
  membrane 
  

   gone, 
  the 
  spindle 
  established, 
  and 
  the 
  chromosomes, 
  which 
  have 
  now 
  

   assumed 
  a 
  somewhat 
  more 
  definite 
  shape, 
  arranged 
  upon 
  it 
  as 
  ir- 
  

   regular 
  spheroids 
  or 
  short 
  rods 
  in 
  an 
  irregular 
  equatorial 
  plate 
  

   (Figs. 
  61—64). 
  At 
  this 
  stage 
  the 
  yolk, 
  as 
  noted 
  by 
  Child 
  (1907, 
  III) 
  

   arranges 
  itself 
  more 
  or 
  less 
  equatorially 
  (Figs. 
  60, 
  62 
  and 
  83). 
  The 
  

   evidence 
  here 
  is 
  strong 
  that, 
  as 
  suggested 
  by 
  many 
  previous 
  writers, 
  

   we 
  are 
  dealing 
  with 
  a 
  force, 
  which, 
  if 
  not 
  actually 
  electrical 
  in 
  

   character, 
  nevertheless 
  acts 
  in 
  a 
  somewhat 
  similar 
  manner, 
  the 
  

   poles 
  of 
  the 
  spindle 
  mutually 
  repelling 
  one 
  another 
  and 
  thereby 
  

   forcing 
  both 
  yolk 
  and 
  chromatin 
  into 
  the 
  egg's 
  equator. 
  It 
  indicates 
  

   moreover 
  that 
  here 
  at 
  least 
  asters 
  and 
  spindle 
  are 
  formed, 
  not 
  thru 
  

   the 
  influence 
  of 
  a 
  centrosome, 
  but 
  rather 
  of 
  a 
  force 
  resident 
  in 
  a 
  

   special 
  cell 
  area. 
  

  

  The 
  form 
  of 
  the 
  aster 
  is 
  subject 
  to 
  considerable 
  variation, 
  

   usually 
  spherical 
  (Figs. 
  59, 
  60, 
  62 
  etc.), 
  it 
  may 
  be 
  oval 
  in 
  outline 
  

   (Fig. 
  61), 
  or 
  even 
  linear 
  (Fig. 
  71). 
  In 
  some 
  cases 
  double 
  asters 
  appear 
  

   giving 
  rise 
  to 
  multipolar 
  spindles 
  (Fig. 
  68). 
  

  

  The 
  number 
  of 
  chromosomes 
  appears 
  to 
  be 
  inconstant 
  in 
  Taenia 
  

   pisiformis. 
  A 
  similar 
  statement 
  has 
  been 
  tentatively 
  made 
  hy 
  Child 
  

   (1907, 
  11); 
  he 
  however 
  does 
  not 
  commit 
  himself 
  to 
  a 
  definite 
  statement. 
  

   To 
  one 
  familiar 
  with 
  cestode 
  material 
  the 
  difficulties 
  in 
  the 
  way 
  of 
  

   making 
  positive 
  assertions 
  on 
  this 
  point 
  will 
  be 
  obvious. 
  The 
  

   arrangement 
  and 
  shape 
  of 
  the 
  chromosomes 
  is 
  in 
  most 
  cases 
  far 
  too 
  

   irregular 
  to 
  admit 
  of 
  definite 
  counts 
  being 
  made. 
  Furthermore 
  in 
  

   material 
  stained 
  in 
  iron 
  haematoxylin 
  yolk 
  granules 
  or 
  other 
  bodies 
  

   may 
  be 
  confused 
  with 
  the 
  chromosomes 
  or 
  vice 
  versa. 
  I 
  have 
  

   however 
  seen 
  a 
  few 
  cases 
  which 
  strongly 
  support 
  this 
  view. 
  

  

  One 
  of 
  these 
  is 
  a 
  side 
  view 
  of 
  a 
  spindle 
  in 
  which 
  a 
  pair 
  of 
  

   divided 
  chromosomes 
  h 
  and 
  h^, 
  are 
  seen 
  with 
  a 
  mid 
  body 
  z, 
  

   between 
  them, 
  and 
  a 
  third 
  chromosome 
  a, 
  just 
  dividing 
  at 
  one 
  

   side 
  of 
  the 
  others 
  (Fig. 
  67). 
  Careful 
  examination 
  of 
  adjoining 
  sections 
  

   shows 
  that 
  no 
  other 
  chromosomes 
  than 
  those 
  shown 
  here 
  are 
  present. 
  

   According 
  to 
  my 
  view 
  there 
  are 
  but 
  three 
  chromosomes 
  in 
  this 
  

   spindle 
  (two 
  divided 
  and 
  one 
  dividing). 
  If 
  however 
  it 
  be 
  admitted 
  

   that 
  the 
  chromosomes 
  here 
  are 
  straggling 
  along 
  the 
  spindle 
  and 
  are 
  

   not 
  dividing 
  at 
  this 
  stage, 
  and 
  that 
  the 
  mid-body 
  is 
  not 
  such 
  a 
  

  

  26* 
  

  

  