﻿378 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  16 
  

  

  that 
  this 
  number 
  may 
  be 
  very 
  much 
  larger 
  under 
  natural 
  conditions. 
  

   It 
  was 
  also 
  observed 
  that 
  during 
  the 
  moulting 
  periods 
  fewer 
  nematodes 
  

   were 
  killed 
  and 
  for 
  a 
  period 
  of 
  one 
  or 
  two 
  days 
  none 
  at 
  all, 
  with 
  a 
  de- 
  

   cided 
  increase 
  after 
  the 
  moult. 
  

  

  When 
  in 
  a 
  resting 
  position, 
  the 
  mononch 
  lay 
  on 
  its 
  side, 
  and 
  never 
  

   oh 
  either 
  its 
  back 
  or 
  "stomach." 
  The 
  body 
  was 
  more 
  or 
  less 
  curved 
  

   ventrally, 
  — 
  the 
  tail 
  end 
  often 
  bent 
  in 
  the 
  form 
  of 
  a 
  spiral. 
  At 
  times 
  

   the 
  whole 
  body 
  was 
  spirally 
  curved. 
  Agar 
  was 
  the 
  best 
  medium 
  for 
  

   the 
  study 
  of 
  the 
  movements. 
  It 
  was 
  seen 
  that 
  locomotion 
  was 
  ac- 
  

   complished 
  by 
  bending 
  in 
  the 
  dorso-ventral 
  plane 
  of 
  the 
  body, 
  this 
  

   plane 
  being 
  placed 
  mostly 
  in 
  a 
  horizontal 
  position 
  so 
  that 
  the 
  dorsal 
  

   and 
  ventral 
  sides 
  were 
  seen 
  in 
  profile. 
  Mononchus 
  papillatus 
  changed 
  

   continually 
  from 
  a 
  moving 
  to 
  a 
  resting 
  state, 
  moving 
  backward 
  as 
  

   well 
  as 
  forward. 
  

  

  In 
  the 
  water-drop 
  cultures 
  with 
  a 
  small 
  amount 
  of 
  soil, 
  the 
  mononchs 
  

   were 
  found 
  only 
  very 
  exceptionally 
  outside 
  the 
  soil 
  area. 
  There 
  was 
  

   a 
  striking 
  difference 
  in 
  the 
  behavior 
  of 
  Mononchus 
  papillatus 
  and 
  the 
  

   Rhabdites 
  added 
  as 
  food. 
  The 
  mononchs 
  seemed 
  to 
  have 
  a 
  more 
  highly 
  

   developed 
  stereotropism, 
  as 
  they 
  remained 
  well 
  hidden 
  in 
  the 
  soil, 
  

   while 
  the 
  Rhabdites 
  were 
  more 
  or 
  less 
  concentrated 
  on 
  the 
  edge 
  of 
  the 
  

   water 
  drop 
  outside 
  the 
  area 
  occupied 
  by 
  the 
  particles 
  of 
  soil. 
  

  

  The 
  sense 
  of 
  touch 
  seemed 
  to 
  be 
  the 
  only 
  sense 
  M. 
  papillatus 
  used 
  

   in 
  hunting 
  about 
  for 
  food. 
  It 
  is 
  known 
  that 
  in 
  nematodes 
  three 
  differ- 
  

   ent 
  kinds 
  of 
  sense-organs 
  may 
  be 
  developed. 
  

  

  1 
  Organs 
  for 
  the 
  sense 
  of 
  touch. 
  — 
  -These 
  are 
  no 
  doubt 
  among 
  the 
  

   chief 
  sense 
  organs 
  of 
  the 
  group 
  and 
  show 
  a 
  high 
  degree 
  of 
  perfection 
  in 
  

   stereotropic 
  reactions 
  and 
  reflex 
  movements. 
  

  

  2 
  Chemical 
  or 
  chemico-physical 
  sense 
  organs, 
  — 
  those 
  known 
  as 
  lateral 
  

   organs 
  or 
  "amphids." 
  In 
  M. 
  ^a^i//a/M5 
  the 
  amphids 
  are 
  rather 
  small 
  

   and 
  inconspicuous. 
  

  

  3 
  Organs 
  for 
  the 
  perception 
  of 
  light. 
  — 
  These 
  are 
  found 
  in 
  many 
  free- 
  

   living 
  nematodes, 
  but 
  are 
  absent 
  in 
  mononchs 
  as 
  well 
  as 
  in 
  most 
  soil 
  

   inhabiting 
  forms. 
  

  

  Judging 
  from 
  the 
  behavior 
  of 
  M. 
  papillatus, 
  the 
  organs 
  of 
  touch 
  were 
  

   probably 
  the 
  only 
  ones 
  used 
  while 
  hunting 
  for 
  food. 
  The 
  nema 
  

   moved 
  through 
  the 
  medium, 
  continually 
  searching 
  its 
  surroundings 
  

   by 
  moving 
  the 
  head 
  end 
  in 
  all 
  possible 
  directions. 
  The 
  head 
  end 
  

   contains 
  the 
  chief 
  organs 
  of 
  touch, 
  as 
  well 
  as 
  those 
  for 
  chemical 
  per- 
  

   ception. 
  After 
  long 
  observations, 
  we 
  came 
  to 
  the 
  conclusion 
  that 
  

   M. 
  papillatus 
  was 
  not 
  able 
  to 
  find 
  its 
  prey 
  at 
  long 
  distance, 
  and 
  the 
  use 
  

  

  