﻿THE 
  MAIOTIO 
  PHASE 
  IN 
  ANIMALS 
  AND 
  PLANTS. 
  513 
  

  

  starting, 
  as 
  has 
  been 
  observed 
  by 
  ourselves 
  and 
  others, 
  from 
  

   many 
  centres. 
  The 
  radiations, 
  however, 
  soon 
  become 
  more 
  

   definitely 
  polarised, 
  and 
  the 
  nuclear 
  wall, 
  often 
  at 
  this 
  time 
  

   showing 
  irregularities 
  in 
  contoui-, 
  gradually 
  disappears, 
  and 
  

   the 
  chromosomes 
  become 
  grouped 
  in 
  the 
  equatorial 
  plane. 
  

   At 
  first 
  they 
  are 
  irregular 
  in 
  their 
  arrangement, 
  but 
  soon 
  

   exhibit 
  the 
  well-known 
  definite 
  plate-like 
  arrangement. 
  The 
  

   achromatic 
  spindle-fibres 
  are 
  very 
  clearly 
  differentiated 
  

   during 
  the 
  movements 
  referred 
  to, 
  and 
  they 
  give 
  the 
  im- 
  

   pression 
  of 
  actively 
  driving 
  the 
  chromosomes 
  to 
  their 
  final 
  

   equatorial 
  positions. 
  We 
  do 
  not 
  adopt 
  this 
  view 
  of 
  their 
  

   nature, 
  as 
  we 
  believe 
  them 
  to 
  represent 
  protoplasm 
  modified 
  

   by 
  the 
  forces 
  at 
  work 
  in 
  the 
  cell 
  rather 
  than 
  actively 
  growing 
  

   entities 
  that 
  are 
  spontaneously 
  concerned 
  in 
  producing 
  the 
  

   movements 
  in 
  question. 
  Thus 
  we 
  consider 
  that 
  the 
  move- 
  

   ment 
  is 
  produced 
  by 
  the 
  same 
  causes 
  that 
  operate 
  so 
  as 
  to 
  

   differentiate 
  the 
  spindle. 
  The 
  latter 
  appears 
  then 
  as 
  a 
  passive 
  

   manifestation 
  of 
  the 
  real 
  operating 
  agency, 
  rather 
  than 
  an 
  

   active 
  director 
  of 
  the 
  movements 
  in 
  question. 
  

  

  Outside 
  the 
  area 
  occupied 
  by 
  the 
  chromosomes 
  isolated 
  

   spindle-fibres, 
  or 
  groups 
  of 
  such, 
  are 
  seen 
  to 
  diverge 
  from 
  the 
  

   main 
  polar 
  directions 
  and 
  to 
  end 
  upon 
  deeply 
  staining 
  droplets 
  

   of 
  nucleolar 
  origin. 
  This 
  fact, 
  long 
  ago 
  pointed 
  out 
  by 
  one 
  of 
  

   us^ 
  (1893), 
  is 
  of 
  special 
  interest 
  as 
  bearing 
  on 
  Strasburger's 
  

   view 
  of 
  the 
  connection 
  of 
  the 
  nucleolus 
  with 
  kinoplasm. 
  

  

  The 
  individual 
  (bivalent) 
  chromosomes 
  assume 
  many 
  

   different 
  forms 
  on 
  the 
  spindle, 
  as 
  has 
  already 
  been 
  pointed 
  

   out 
  by 
  us 
  in 
  a 
  previous 
  paper;" 
  but 
  during 
  the 
  metaphase 
  

   one 
  general 
  mode 
  of 
  procedure 
  is 
  seen 
  to 
  govern 
  their 
  

   division. 
  Each 
  bivalent 
  chromosome 
  divides 
  so 
  as 
  to 
  

   separate 
  monovalent 
  elements, 
  which 
  are 
  then 
  distributed 
  

   to 
  the 
  respective 
  poles. 
  The 
  mode 
  of 
  separation 
  varies 
  

   in 
  the 
  case 
  of 
  different 
  chromosomes, 
  the 
  difference 
  depend- 
  

   ing 
  on 
  the 
  manner 
  in 
  which 
  the 
  latter 
  are 
  arranged 
  with 
  

  

  ' 
  J. 
  B. 
  Farmer, 
  ' 
  Annals 
  of 
  Botany,' 
  vol. 
  vii, 
  1893; 
  cf. 
  also 
  ' 
  Flora,' 
  1895. 
  

   ^ 
  " 
  On 
  the 
  Essential 
  Similarities 
  existing 
  between 
  the 
  Heterotype 
  Nuclear 
  

   Divisions 
  in 
  Animals 
  and 
  Plants," 
  ' 
  Auat. 
  Anzeiger.,' 
  1895. 
  

  

  