﻿THE 
  MAIOTIC 
  PHASE 
  IN 
  ANIMALS 
  AND 
  PLANTS. 
  549 
  

  

  highest 
  flowering 
  plants, 
  the 
  formation 
  of 
  the 
  ovum- 
  (oosphere) 
  

   is 
  only 
  separated 
  from 
  it 
  by 
  a 
  single 
  mitosis. 
  In 
  these 
  cases 
  

   it 
  appears 
  probable 
  that 
  the 
  small 
  number 
  has 
  been 
  brought 
  

   about 
  by 
  a 
  process 
  of 
  shortening 
  the 
  life 
  histor}^, 
  and 
  it 
  is 
  

   probably 
  correct 
  to 
  say, 
  for 
  the 
  great 
  majority 
  of 
  plants 
  at 
  

   any 
  rate, 
  that 
  the 
  occurrence 
  of 
  a 
  number 
  of 
  post-maiotic 
  

   cell-generations 
  is 
  the 
  rule. 
  

  

  The 
  facts 
  of 
  reduction, 
  as 
  set 
  forth 
  in 
  this 
  paper, 
  appear 
  to 
  

   afford 
  strong 
  grounds 
  for 
  supposing 
  the 
  chromosomes 
  to 
  be 
  

   permanent 
  structures 
  that 
  retain 
  their 
  identity 
  from 
  one 
  

   generation 
  to 
  another 
  in 
  the 
  individuals 
  composing 
  a 
  species. 
  

   This 
  aspect 
  of 
  the 
  question 
  has 
  already 
  been 
  touched 
  on 
  in 
  the 
  

   Introduction, 
  but 
  its 
  importance 
  is 
  so 
  great 
  that 
  a 
  few 
  addi- 
  

   tional 
  remarks 
  are 
  called 
  for 
  here. 
  

  

  We 
  have 
  seen 
  that, 
  notwithstanding 
  the 
  impossibility 
  of 
  

   recognising 
  the 
  delimitation 
  of 
  a 
  chromosome 
  in 
  the 
  resting 
  

   nucleus, 
  the 
  chromatin 
  or 
  nuclein 
  nevertheless 
  does 
  aggregate 
  

   in 
  thelinin, 
  at 
  the 
  very 
  commencement 
  of 
  prophase, 
  in 
  such 
  

   a 
  way 
  that 
  it 
  is 
  difl&cult 
  to 
  escape 
  the 
  inference 
  that 
  the 
  

   reconstitution 
  of 
  the 
  chromosome 
  represents, 
  mutatis 
  

   mutandis, 
  the 
  exact 
  converse 
  of 
  the 
  series 
  of 
  changes 
  

   witnessed 
  during 
  the 
  preceding 
  telophase. 
  Many 
  other 
  

   authors 
  have 
  been 
  driven 
  to 
  a 
  similar 
  conclusion, 
  and 
  Ave 
  

   think 
  that 
  in 
  favourable 
  instances, 
  such 
  as 
  those 
  of 
  Trades- 
  

   cantia 
  and 
  Periplaneta, 
  the 
  evidence 
  in 
  support 
  of 
  the 
  view 
  

   that 
  would 
  regard 
  the 
  whole 
  process 
  as 
  an 
  unravelling, 
  rather 
  

   than 
  as 
  a 
  new 
  construction, 
  is 
  extremely 
  cogent. 
  The 
  close 
  

   correspondence 
  between 
  the 
  actual 
  primordia 
  of 
  the 
  chromo- 
  

   somes, 
  before 
  the 
  spirem 
  thread 
  is 
  built 
  up, 
  and 
  the 
  vacuo- 
  

   lating 
  chromosomes 
  of 
  the 
  telophase 
  can 
  hardly 
  be 
  accidental, 
  

   and, 
  moreover, 
  the 
  evidence 
  based 
  on 
  the 
  identity 
  in 
  numbers 
  

   cannot 
  be 
  disregarded. 
  

  

  Again, 
  the 
  nature 
  of 
  a 
  reduction 
  which 
  resolves 
  itself 
  into 
  

   a 
  sorting 
  of 
  chromosomes 
  rather 
  than 
  that 
  of 
  a 
  mere 
  halving 
  

   of 
  chromatic 
  substance 
  is 
  not 
  easy 
  to 
  explain 
  apart 
  from 
  the 
  

   existence 
  of 
  a 
  specific 
  individuality 
  that 
  is 
  vested 
  in 
  each 
  one 
  

   of 
  the 
  structures 
  in 
  question. 
  

  

  