﻿550 
  J. 
  BRETLAND 
  FARMER 
  AND 
  J. 
  E. 
  S. 
  MOOEE. 
  

  

  And 
  finally, 
  the 
  reappearance 
  during 
  a 
  long 
  series 
  of 
  divi- 
  

   sions 
  of 
  chromosomes 
  that 
  can 
  be 
  recognised 
  by 
  some 
  

   peculiarity 
  such 
  as 
  that 
  of 
  size, 
  as 
  in 
  the 
  case 
  of 
  Brachy- 
  

   stola 
  mentioned 
  by 
  Sutton/ 
  as 
  well 
  as 
  the 
  remarkable 
  

   features 
  to 
  be 
  observed 
  during 
  the 
  heterotype 
  mitosis 
  of 
  

   Drosera 
  hybrids 
  described 
  by 
  Rosenberg,^ 
  appear 
  only 
  to 
  

   find 
  a 
  satisfactory 
  explanation 
  on 
  the 
  assumption 
  of 
  persistent 
  

   identity. 
  

  

  It 
  will 
  be 
  remembered 
  that 
  Rosenberg 
  found 
  that 
  in 
  

   Drosera 
  rotundifolia 
  there 
  were 
  twenty, 
  in 
  D. 
  longi- 
  

   folia 
  ten, 
  chromosomes 
  during 
  maiosis. 
  Consequently, 
  in 
  

   the 
  hybrid 
  forms 
  there 
  were 
  normally 
  thirty 
  in 
  each 
  somatic 
  

   nucleus. 
  When 
  reduction 
  supervened, 
  it 
  might 
  have 
  been 
  

   anticipated 
  that 
  fifteen 
  would 
  have 
  been 
  the 
  number 
  pro- 
  

   duced. 
  Instead 
  of 
  this, 
  Rosenberg 
  found 
  in 
  every 
  case 
  that 
  

   twenty 
  were 
  present. 
  But 
  of 
  the 
  twenty, 
  ten 
  were 
  large 
  

   and 
  ten 
  were 
  small 
  ; 
  and 
  the 
  inference 
  drawn 
  by 
  him 
  was 
  that 
  

   the 
  ten 
  large 
  ones 
  were 
  bivalent, 
  resulting 
  from 
  the 
  union 
  of 
  

   pairs 
  derived 
  respectively 
  from 
  D. 
  longi 
  folia 
  and 
  D. 
  

   rotundifolia, 
  whilst 
  the 
  ten 
  small 
  ones 
  represented 
  single 
  

   chromosomes 
  that 
  originated 
  from 
  the 
  surplus 
  number 
  (ten) 
  

   of 
  chromosomes 
  belonging 
  to 
  the 
  rotundifolia 
  parent. 
  

  

  It 
  is, 
  however, 
  equally 
  clear 
  that 
  a 
  change, 
  probably 
  of 
  the 
  

   nature 
  of 
  re-arrangement, 
  may 
  at 
  least 
  occasionally 
  occur 
  in 
  

   both 
  a 
  plant 
  and 
  an 
  animal. 
  For 
  whilst 
  there 
  is 
  a 
  striking 
  

   degree 
  of 
  constancy 
  manifested 
  in 
  the 
  number 
  of 
  the 
  chromo- 
  

   somes 
  characteristic 
  of 
  a 
  species, 
  it 
  by 
  no 
  means 
  follows 
  that 
  

   closely 
  related 
  species 
  possess 
  closely 
  related 
  numbers, 
  such 
  

   as 
  multiples 
  of 
  one 
  another. 
  

  

  The 
  various 
  species 
  of 
  lilies 
  or 
  of 
  As 
  car 
  is 
  afford 
  examples 
  

   of 
  the 
  truth 
  of 
  this 
  statement. 
  Possibly 
  the 
  alteration 
  in 
  the 
  

   number 
  of 
  chromosomes 
  may 
  be 
  correlated 
  with 
  an 
  alteration 
  

   of 
  specific 
  characters 
  such 
  as 
  bring 
  about 
  what 
  De 
  Vries 
  has 
  

   termed 
  " 
  mutations." 
  But 
  be 
  this 
  as 
  it 
  may, 
  it 
  is 
  clear 
  that 
  

  

  ' 
  W. 
  S. 
  Sutton, 
  " 
  On 
  the 
  Morphology 
  of 
  the 
  Chromosome 
  group 
  in 
  

   Brachystola 
  magna," 
  'Biol. 
  Bull.,' 
  iv. 
  

  

  1 
  Rosenberg, 
  ' 
  Ber. 
  Deutsche 
  Bot. 
  Geseilsch.,' 
  1904i. 
  

  

  