﻿370 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  16 
  

  

  ments 
  showed 
  that 
  sandy 
  soil 
  as 
  well 
  as 
  other 
  kinds 
  may 
  be 
  used. 
  

  

  3. 
  It 
  should 
  be 
  seen 
  to 
  that 
  the 
  soil 
  be 
  free 
  from 
  decaying 
  matter. 
  

  

  4. 
  If 
  possible 
  the 
  water, 
  and 
  even 
  the 
  soil, 
  should 
  be 
  changed 
  

   daily. 
  Mononchus 
  papillatus 
  seems 
  to 
  be 
  very 
  susceptible 
  to 
  any 
  

   pollution, 
  especially 
  bacterial 
  {B. 
  subtilis 
  typ.). 
  

  

  It 
  seems 
  very 
  astonishing 
  at 
  first 
  that 
  the 
  simple 
  addition 
  of 
  a 
  small 
  

   amount 
  of 
  soil 
  should 
  be 
  of 
  such 
  great 
  importance 
  to 
  the 
  growth 
  and 
  

   life 
  of 
  these 
  nemas. 
  It 
  was 
  found 
  that 
  soil 
  was 
  absolutely 
  essential 
  

   for 
  the 
  keeping 
  alive 
  of 
  newly 
  hatched 
  larvae 
  and 
  for 
  rearing 
  them. 
  

  

  C. 
  The 
  agar-cuUure 
  method. 
  — 
  In 
  1914 
  Berliner 
  and 
  Busch 
  described 
  

   a 
  method 
  for 
  rearing 
  Heterodera 
  schachiii 
  Schmidt 
  on 
  agar 
  plates. 
  

   Agar 
  was 
  carefully 
  washed, 
  sterilized 
  and 
  poured 
  into 
  petri 
  dishes. 
  

   Sterilized 
  seeds 
  of 
  oats, 
  turnips, 
  beets 
  and 
  different 
  varieties 
  of 
  vetch 
  

   and 
  clover 
  were 
  planted 
  on 
  the 
  agar 
  and 
  eggs 
  or 
  larvae 
  of 
  Heterodera 
  

   schachtii 
  added. 
  This 
  seemed 
  to 
  be 
  a 
  very 
  simple 
  and 
  useful 
  method 
  

   also 
  for 
  our 
  purpose, 
  it 
  being 
  only 
  necessary 
  to 
  add 
  the 
  mononchs 
  to 
  

   get 
  a 
  complete 
  food 
  cycle, 
  — 
  Heterodera 
  feeding 
  on 
  the 
  roots 
  of 
  the 
  

   growing 
  plant 
  and 
  Mononchus 
  feeding 
  on 
  Heterodera. 
  Byars 
  in 
  1914 
  

   also 
  described 
  a 
  similar 
  method 
  for 
  rearing 
  Heterodera 
  radicicola. 
  

   Had 
  good 
  results 
  been 
  obtained, 
  it 
  would 
  have 
  shown 
  very 
  beautifully 
  

   the 
  relationship 
  between 
  these 
  two 
  forms 
  of 
  soil 
  nemas 
  ; 
  but 
  difficulties 
  

   soon 
  arose. 
  In 
  the 
  first 
  place 
  Heterodera 
  radicicola, 
  the 
  form 
  used 
  for 
  

   infecting 
  the 
  roots, 
  did 
  not 
  attack 
  them 
  (oats, 
  cucumbers) 
  and 
  up 
  to 
  

   the 
  present 
  time 
  our 
  experiments 
  along 
  this 
  line 
  have 
  not 
  been 
  satis- 
  

   f 
  actor)/. 
  The 
  mononchs 
  were 
  already 
  feeding 
  on 
  the 
  Heterodera 
  

   and 
  seemed 
  to 
  thrive 
  in 
  the 
  agar, 
  moving 
  constantly 
  around, 
  

   even 
  laying 
  a 
  number 
  of 
  eggs. 
  So 
  we 
  added 
  more 
  food 
  for 
  

   them, 
  consisting 
  of 
  Rhabditis 
  pellio, 
  Rh. 
  elegans, 
  Anguillula 
  aceti, 
  and 
  

   Heterodera 
  radicicola. 
  By 
  this 
  time 
  the 
  bacterial 
  infection 
  of 
  the 
  plate 
  

   grew 
  so 
  heavy 
  that 
  the 
  mononchs 
  died. 
  Young 
  larvae 
  already 
  

   hatched 
  from 
  the 
  eggs 
  also 
  died, 
  even 
  in 
  freshly 
  prepared 
  and 
  non- 
  

   infected 
  agar. 
  Thus 
  it 
  seems 
  to 
  us 
  that 
  the 
  agar 
  method 
  may 
  be 
  used 
  

   only 
  for 
  larvae 
  a 
  week 
  or 
  more 
  old, 
  and 
  adults, 
  and 
  then 
  the 
  agar 
  

   should 
  be 
  changed 
  every 
  eight 
  to 
  fourteen 
  days. 
  

  

  A 
  further 
  inconvenience 
  consisted 
  in 
  the 
  size 
  of 
  the 
  plate, 
  since 
  on 
  

   even 
  the 
  smallest 
  plates 
  it 
  was 
  quite 
  difficult 
  to 
  find 
  the 
  nemas 
  and 
  

   eggs 
  again, 
  because 
  of 
  the 
  rapid 
  wandering 
  of 
  the 
  former 
  through 
  the 
  

   agar 
  and 
  the 
  minuteness 
  of 
  the 
  latter. 
  

  

  The 
  second 
  method, 
  that 
  of 
  using 
  concave 
  slides 
  with 
  a 
  small 
  

   quantity 
  of 
  soil 
  in 
  a 
  drop 
  of 
  water, 
  seemed 
  best 
  fitted 
  for 
  our 
  purpose, 
  

  

  