﻿A 
  Further 
  Study 
  of 
  Chromosome 
  Dimensions. 
  159 
  

  

  evolutionary 
  development. 
  When 
  the 
  length 
  limit 
  has 
  again 
  been 
  reached, 
  

   conjugation 
  of 
  units 
  once 
  more 
  takes 
  place, 
  followed 
  by 
  segmentation 
  into 
  

   spherical 
  chromosomes 
  of 
  a 
  doubled 
  diameter 
  ; 
  and 
  further 
  evolutionary 
  

   development 
  of 
  the 
  animal 
  is 
  again 
  accompanied 
  by 
  conversion 
  of 
  these 
  

   spherical 
  chromosomes 
  into 
  rods 
  of 
  various 
  lengths 
  by 
  linear 
  growth. 
  

  

  This 
  hypothesis 
  seemed 
  to 
  accord 
  with 
  the 
  phenomena 
  observed. 
  But 
  the 
  

   number 
  of 
  animals 
  that 
  I 
  had 
  studied 
  was 
  small, 
  and 
  many 
  phyla 
  had 
  been 
  

   represented 
  in 
  my 
  investigations 
  by 
  only 
  one 
  species 
  ; 
  moreover, 
  the 
  diffi- 
  

   culties 
  inherent 
  in 
  the 
  measurement 
  of 
  chromosomes, 
  combined 
  with 
  my 
  

   inability 
  to 
  eliminate 
  the 
  personal 
  factor 
  from 
  my 
  drawings, 
  increased 
  the 
  

   possibility 
  of 
  error. 
  I 
  drew 
  attention 
  to 
  this 
  at 
  the 
  time, 
  in 
  order 
  that 
  

   premature 
  and 
  undue 
  importance 
  might 
  not 
  be 
  attached 
  to 
  the 
  hypothesis, 
  

   but 
  added 
  the 
  hope 
  that 
  it 
  would 
  be 
  valuable, 
  whether 
  eventually 
  proved 
  or 
  

   disproved, 
  in 
  that 
  it 
  suggested 
  a 
  new 
  line 
  of 
  thought. 
  

  

  The 
  subject 
  was 
  later 
  studied 
  by 
  Fanner 
  and 
  Digb'y, 
  who 
  published 
  early 
  

   in 
  1914 
  the 
  results 
  of 
  a 
  series 
  of 
  measurements 
  of 
  chromosomes 
  in 
  both 
  

   animals 
  and 
  plants. 
  These 
  results 
  partly 
  corroborated 
  and 
  partly 
  disagreed 
  

   with 
  my 
  earlier 
  observations. 
  On 
  the 
  one 
  hand, 
  they 
  showed 
  a 
  tendency 
  

   for 
  the 
  chromosome 
  diameter 
  to 
  increase 
  as 
  we 
  passed 
  from 
  simple 
  to 
  

   complex 
  animals, 
  and 
  further 
  showed 
  that 
  this 
  tendency 
  extended 
  to 
  the 
  

   plant 
  kingdom, 
  which 
  I 
  had 
  not 
  studied. 
  The 
  similarity 
  shown 
  between 
  the 
  

   complexes 
  of 
  animals 
  and 
  plants 
  was 
  in 
  many 
  ways 
  remarkable. 
  On 
  the 
  

   other 
  hand, 
  they 
  proved 
  that 
  the 
  number 
  of 
  different 
  chromosome 
  diameters 
  

   is 
  greater 
  than 
  I 
  had 
  suspected 
  ; 
  that 
  chromosomes 
  composing 
  an 
  individual 
  

   complex 
  can 
  be 
  of 
  different 
  diameters 
  ; 
  and 
  that 
  the 
  chromosome 
  diameters 
  

   in 
  Homarus 
  gammarus 
  are 
  much 
  smaller 
  than 
  those 
  in 
  the 
  closely 
  allied 
  

   Palcemon 
  serratus. 
  

  

  This 
  evidence 
  directly 
  affected 
  my 
  fourth 
  generalisation, 
  previously 
  

   mentioned 
  ; 
  for, 
  while 
  suggesting 
  correlation 
  between 
  chromosome 
  diameter 
  

   and 
  the 
  degree 
  of 
  somatic 
  complexity, 
  it 
  proved 
  that 
  intimate 
  and 
  uniformly 
  

   observable 
  correlation 
  could 
  no 
  longer 
  be 
  proposed. 
  In 
  the 
  circumstances, 
  

   this 
  generalisation 
  became 
  modified 
  accordingly. 
  

  

  In 
  order 
  to 
  obtain 
  further 
  data 
  concerning 
  the 
  third 
  generalisation, 
  and 
  

   the 
  fourth 
  in 
  its 
  amended 
  form, 
  I 
  turned 
  in 
  the 
  spring 
  of 
  1914 
  from 
  spindle 
  

   measurements 
  to 
  the 
  study 
  of 
  chromosome 
  dimensions 
  in 
  the 
  spermatogenetic 
  

   mitoses 
  of 
  animals 
  that 
  I 
  had 
  not 
  previously 
  dealt 
  with. 
  I 
  found 
  new 
  and 
  

   important 
  evidence, 
  particularly 
  in 
  Smerinthus 
  populi, 
  Vanessa 
  urticai, 
  and 
  

   Gallus 
  domesticus. 
  This 
  evidence 
  was 
  supplemented 
  shortly 
  afterwards 
  in 
  a 
  

   study 
  of 
  these 
  mitoses 
  in 
  Felis, 
  of 
  which 
  preparations 
  were 
  lent 
  to 
  me 
  by 
  

   Dr. 
  H. 
  de 
  Winiwarter 
  ; 
  and 
  I 
  take 
  this 
  opportunity 
  of 
  thanking 
  him 
  again 
  

  

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