﻿718 
  Fluctuations 
  

  

  bility 
  falls 
  under 
  two 
  heads. 
  They 
  obey 
  quite 
  

   the 
  same 
  laws 
  and 
  are 
  therefore 
  easily 
  confused, 
  

   but 
  with 
  respect 
  to 
  questions 
  of 
  heredity 
  they 
  

   should 
  be 
  carefully 
  separated. 
  They 
  are 
  des- 
  

   ignated 
  by 
  the 
  terms 
  individual 
  and 
  partial 
  

   fluctuation. 
  Individual 
  variability 
  indicates 
  

   the 
  differences 
  between 
  individuals, 
  while 
  

   partial 
  variability 
  is 
  limited 
  to 
  the 
  devia- 
  

   tions 
  shown 
  by 
  the 
  parts 
  of 
  one 
  organ- 
  

   ism 
  from 
  the 
  average 
  structure. 
  The 
  same 
  

   qualities 
  in 
  some 
  cases 
  vary 
  individually 
  and 
  in 
  

   others 
  partially. 
  Even 
  stature, 
  which 
  is 
  as 
  

   markedly 
  individual 
  for 
  annual 
  and 
  biennial 
  

   plants 
  as 
  it 
  is 
  for 
  man, 
  becomes 
  partially 
  variant 
  

   in 
  the 
  case 
  of 
  perennial 
  herbs 
  with 
  numbers 
  of 
  

   stems. 
  Often 
  a 
  character 
  is 
  only 
  developed 
  once 
  

   in 
  the 
  whole 
  course 
  of 
  evolution, 
  as 
  for 
  instance, 
  

   the 
  degree 
  of 
  connation 
  of 
  the 
  seed-leaves 
  in 
  

   tricotyls 
  and 
  in 
  numerous 
  cases 
  it 
  is 
  impos- 
  

   sible 
  to 
  tell 
  whether 
  a 
  character 
  is 
  individual 
  or 
  

   partial. 
  Consequently 
  such 
  minute 
  details 
  

   are 
  generally 
  considered 
  to 
  have 
  no 
  real 
  im- 
  

   portance 
  for 
  the 
  hereditary 
  transmission 
  of 
  the 
  

   character 
  under 
  discussion. 
  

  

  Fluctuations 
  are 
  observed 
  to 
  take 
  place 
  only 
  

   in 
  two 
  directions. 
  The 
  quality 
  may 
  increase 
  or 
  

   decrease, 
  but 
  is 
  not 
  seen 
  to 
  vary 
  in 
  any 
  other 
  

   way. 
  This 
  rule 
  is 
  now 
  widely 
  established 
  by 
  

   numerous 
  investigations, 
  and 
  is 
  fundamental 
  to 
  

  

  