﻿158 
  

  

  Mr. 
  C. 
  F. 
  U. 
  Meek. 
  

  

  lengths 
  of 
  the 
  chromosomes 
  composing 
  its 
  complex. 
  This 
  generalisation 
  was 
  

   proved 
  by 
  the 
  data 
  collected 
  : 
  for, 
  passing 
  through 
  the 
  various 
  phyla, 
  from 
  

   simple 
  to 
  highly 
  differentiated 
  animals, 
  no 
  tendency 
  could 
  be 
  found 
  for 
  the 
  

   chromosomes 
  of 
  the 
  complex 
  to 
  become 
  either 
  longer 
  or 
  shorter 
  ; 
  and, 
  

   outside 
  small 
  divisions 
  of 
  the 
  animal 
  kingdom, 
  our 
  systematic 
  classification 
  

   gave 
  no 
  clue 
  to 
  the 
  lengths 
  in 
  the 
  complex 
  of 
  any 
  particular 
  animal. 
  

  

  The 
  second 
  generalisation 
  was 
  that 
  the 
  degree 
  of 
  somatic 
  complexity 
  of 
  

   an 
  animal 
  cannot 
  be 
  correlated 
  with 
  the 
  number 
  of 
  the 
  chromosomes 
  

   composing 
  its 
  complex. 
  This 
  was 
  likewise 
  proved 
  by 
  the 
  data 
  collected 
  : 
  

   for 
  no 
  tendency 
  could 
  be 
  found 
  for 
  highly 
  differentiated 
  animals 
  to 
  possess 
  

   either 
  more 
  or 
  fewer 
  chromosomes 
  than 
  are 
  possessed 
  by 
  low 
  and 
  simple 
  

   animals 
  ; 
  and, 
  outside 
  small 
  divisions, 
  our 
  systematic 
  classification 
  again 
  

   constituted 
  no 
  index. 
  

  

  The 
  third 
  generalisation 
  was 
  that 
  correlation 
  exists 
  between 
  the 
  degree 
  

   of 
  somatic 
  complexity 
  of 
  an 
  animal 
  and 
  the 
  total 
  volume 
  of 
  the 
  chromo- 
  

   somes 
  composing 
  its 
  complex. 
  My 
  data 
  showed 
  a 
  tendency 
  for 
  the 
  total 
  

   volume 
  of 
  chromatin 
  on 
  the 
  spindles 
  to 
  increase 
  as 
  we 
  passed 
  from 
  simple 
  to 
  

   complex 
  animals, 
  although 
  strict 
  uniformity 
  in 
  this 
  was 
  not 
  observed. 
  This 
  

   generalisation 
  was 
  therefore 
  suggested 
  by 
  the 
  results 
  obtained. 
  

  

  The 
  fourth 
  and 
  last 
  generalisation 
  was 
  that 
  correlation 
  exists 
  between 
  the 
  

   degree 
  of 
  somatic 
  complexity 
  of 
  an 
  animal 
  and 
  the 
  diameter 
  of 
  the 
  chromo- 
  

   somes 
  composing 
  its 
  complex. 
  Whereas 
  the 
  lengths 
  of 
  the 
  chromosomes 
  had 
  

   been 
  found 
  to 
  be 
  arbitrary, 
  the 
  diameters 
  seemed 
  to 
  fall 
  into 
  three 
  definite 
  

   groups. 
  The 
  diameters 
  in 
  Protozoa 
  were 
  observed 
  to 
  be 
  equal 
  to 
  half 
  those 
  

   in 
  low 
  Metazoa, 
  while 
  the 
  diameters 
  in 
  low 
  Metazoa 
  were 
  observed 
  to 
  be 
  

   equal 
  to 
  half 
  those 
  in 
  high 
  Metazoa. 
  This 
  generalisation 
  was 
  therefore 
  

   suggested 
  by 
  the 
  results 
  obtained, 
  and, 
  since 
  my 
  data 
  showed 
  no 
  exceptions, 
  

   strict 
  correlation 
  was 
  proposed. 
  

  

  In 
  consideration 
  of 
  the 
  evidence 
  before 
  me, 
  I 
  constructed 
  a 
  working 
  

   hypothesis. 
  I 
  suggested 
  that 
  the 
  chromatin 
  granules 
  of 
  the 
  simplest 
  

   Protozoa 
  are 
  converted 
  into 
  rods 
  by 
  linear 
  growth, 
  accompanying 
  evolu- 
  

   tionary 
  development 
  and 
  increased 
  complexity 
  of 
  the 
  animal; 
  the 
  rate 
  of 
  

   growth 
  is 
  not 
  the 
  same 
  in 
  all 
  chromosomes, 
  and 
  rods 
  of 
  various 
  lengths 
  are 
  

   therefore 
  evolved. 
  A 
  stage 
  in 
  phylogeny 
  is 
  reached 
  later, 
  when 
  chromo- 
  

   somes 
  have 
  attained 
  a 
  maximum 
  length, 
  the 
  limit 
  depending 
  upon 
  physical 
  

   conditions, 
  possibly 
  connected 
  with 
  spindle 
  mechanism 
  ; 
  when 
  this 
  occurs, 
  

   chromatin 
  units 
  conjugate 
  in 
  fours, 
  and 
  the 
  resulting 
  chromosomes 
  have 
  a 
  

   diameter 
  equal 
  to 
  twice 
  that 
  previously 
  seen. 
  These 
  then 
  segment 
  into 
  

   spherical 
  chromosomes 
  of 
  the 
  new 
  diameter, 
  and 
  such 
  chromosomes 
  are 
  

   prepared 
  to 
  enter 
  a 
  new 
  course 
  of 
  linear 
  growth, 
  accompanying 
  further 
  

  

  