﻿OCT. 
  4, 
  1922 
  STEINER 
  AND 
  HEINLY 
  : 
  CONTROL 
  OF 
  INJURIOUS 
  NEMAS 
  383 
  

  

  between 
  these 
  forms 
  and 
  other 
  members 
  of 
  the 
  community 
  of 
  living 
  

   forms 
  that 
  exist 
  there, 
  and 
  of 
  their 
  relationships 
  to 
  other 
  nematode 
  

   species. 
  

  

  VIII. 
  THE 
  soil., 
  ITS 
  LIFE 
  AND 
  THE 
  NUMBER 
  OF 
  NEMATODES, 
  ESPECIALLY 
  

  

  OF 
  PREDATORY 
  FORMS 
  THEREIN 
  

  

  Our 
  knowledge 
  of 
  life 
  in 
  the 
  soil, 
  especially 
  of 
  microscopic 
  life 
  there, 
  is 
  

   still 
  very 
  restricted. 
  We 
  know 
  very 
  little 
  about 
  the 
  relationships 
  that 
  

   exist 
  between 
  the 
  living 
  components 
  of 
  the 
  soil, 
  and 
  often 
  we 
  do 
  not 
  

   even 
  know 
  these 
  components. 
  Certainly 
  soil 
  fertility 
  does 
  not 
  de- 
  

   pend 
  entirely 
  upon 
  its 
  chemical, 
  colloidal 
  and 
  physical 
  nature, 
  but 
  also 
  

   and 
  probably 
  largely, 
  upon 
  the 
  animal 
  and 
  plant 
  life 
  therein. 
  The 
  

   importance 
  of 
  soil 
  bacteria 
  is 
  already 
  known 
  and 
  there 
  exists 
  a 
  close 
  

   relationship 
  between 
  these 
  bacteria 
  and 
  the 
  nematode 
  population, 
  as 
  

   a 
  large 
  number 
  of 
  nemas 
  are 
  bacteria 
  consumers. 
  Investigations 
  

   carried 
  on 
  throughout 
  more 
  recent 
  years 
  have 
  definitely 
  proved 
  that 
  the 
  

   soil 
  contains 
  an 
  enormous 
  number 
  of 
  nematodes, 
  and 
  that, 
  next 
  to 
  

   bacteria, 
  they 
  form 
  probably 
  the 
  largest 
  constituent 
  element 
  in 
  sub- 
  

   terranean 
  life. 
  Numerous 
  new 
  species 
  have 
  been 
  described 
  and 
  all 
  

   investigators 
  agree 
  that 
  there 
  is 
  an 
  enormous 
  number 
  still 
  undescribed. 
  

   It 
  will 
  require 
  the 
  collaboration 
  of 
  many 
  research 
  workers 
  to 
  describe 
  

   all 
  these 
  forms. 
  A 
  nema 
  species 
  may 
  furnish 
  millions 
  of 
  individuals 
  to 
  

   ever}^' 
  acre 
  of 
  our 
  fields. 
  No 
  exact 
  records 
  regarding 
  the 
  number 
  

   have 
  been 
  published 
  so 
  far. 
  Dr. 
  Cobb 
  kindly 
  placed 
  at 
  our 
  disposal 
  

   some 
  of 
  his 
  tables 
  from 
  field 
  surveys. 
  The 
  results 
  of 
  the 
  surveys 
  

   shown 
  below 
  are 
  of 
  great 
  interest. 
  

  

  Minimum 
  number 
  of 
  nematodes 
  per 
  

   acre, 
  top 
  six 
  inches 
  (15.2 
  cm.) 
  

  

  From 
  Missouri 
  corn 
  field 
  648,000,000 
  

  

  From 
  North 
  Carolina 
  field 
  242,400,000 
  

  

  From 
  New 
  Jersey 
  field 
  129,600,000 
  

  

  From 
  Rhode 
  Island 
  field 
  610,800,000 
  

  

  From 
  New 
  Hampshire 
  field 
  99,600,000 
  

  

  From 
  Minnesota 
  field 
  121,200,000 
  

  

  From 
  Vermont 
  field 
  580,000,000 
  

  

  From 
  Kansas 
  field 
  278,400,000 
  

  

  These 
  tables 
  give 
  only 
  the 
  minimum 
  numbers 
  arid 
  are 
  figures 
  taken 
  

   from 
  a 
  study 
  of 
  only 
  the 
  top 
  six 
  inches 
  (15 
  cm.) 
  . 
  A 
  maximum 
  penetra- 
  

   tion 
  of 
  some 
  nema 
  species 
  has 
  been 
  observed 
  to 
  be 
  as 
  much 
  as 
  (7-8 
  m.) 
  

   25 
  feet. 
  These 
  unpublished 
  observations 
  were 
  made 
  by 
  Dr. 
  Cobb 
  on 
  

   citrus 
  trees 
  in 
  California 
  and 
  on 
  alfalfa 
  roots 
  in 
  New 
  South 
  Wales. 
  

  

  