﻿84 
  E. 
  J. 
  ALLEN. 
  

  

  confirmed 
  by 
  the 
  appearance 
  presented 
  by 
  food-masses 
  in 
  the 
  

   intestine^ 
  as 
  seen 
  in 
  sections 
  of 
  preserved 
  material, 
  wliicli 
  

   generally 
  show 
  skeletons 
  of 
  diatoms, 
  etc. 
  

  

  When 
  removed 
  from 
  its 
  tube 
  and 
  irritated, 
  Pcecilocha3tus 
  

   often 
  swims 
  with 
  a 
  rapid, 
  serpentine 
  motion, 
  which 
  recalls 
  

   the 
  motion 
  of 
  the 
  larva. 
  

  

  Specimens 
  were 
  easily 
  kept 
  alive 
  for 
  some 
  weeks 
  in 
  the 
  

   Laboratory 
  when 
  provided 
  with 
  sand 
  in 
  which 
  to 
  construct 
  

   their 
  tubes, 
  and 
  worms 
  which 
  through 
  injury 
  had 
  lost 
  the 
  

   posterior 
  part 
  of 
  their 
  bodies 
  generally 
  regenerated 
  new 
  tail 
  

   ends 
  of 
  characteristic 
  structure. 
  

  

  Pcecilocha3tus 
  appears 
  to 
  breed 
  practically 
  the 
  whole 
  

   year 
  round. 
  Specimens 
  were 
  taken 
  in 
  February, 
  April, 
  

   May, 
  June, 
  August 
  and 
  December, 
  and 
  on 
  all 
  occasions 
  some 
  

   were 
  found 
  to 
  contain 
  almost 
  or 
  quite 
  mature 
  eggs 
  or 
  

   spermatozoa. 
  The 
  mode 
  in 
  which 
  the 
  eggs 
  are 
  laid 
  has 
  not 
  

   been 
  determined. 
  The 
  larva 
  of 
  Pcecilochfetus 
  is 
  remarkable 
  

   for 
  the 
  late 
  stage 
  of 
  development 
  to 
  which 
  it 
  retains 
  the 
  

   pelagic 
  habit. 
  

  

  Methods. 
  

  

  As 
  careful 
  a 
  study 
  as 
  possible 
  was 
  made 
  of 
  the 
  living 
  worm. 
  

   For 
  further 
  examination 
  specimens 
  were 
  preserved 
  by 
  the 
  

   methods 
  to 
  be 
  described. 
  The 
  worms 
  were 
  antesthetised 
  by 
  

   the 
  gradual 
  addition 
  of 
  alcohol 
  to 
  the 
  sea-water 
  in 
  which 
  they 
  

   were 
  living. 
  They 
  were 
  then 
  placed 
  on 
  a 
  glass 
  plate 
  and 
  

   killed 
  by 
  dropping 
  on 
  to 
  them 
  a 
  small 
  quantity 
  of 
  the 
  pre- 
  

   serving 
  fluid 
  to 
  be 
  employed, 
  the 
  worms 
  being 
  kept 
  straight 
  

   and 
  extended 
  with 
  camel's-hair 
  brushes 
  until 
  contraction 
  had 
  

   ceased. 
  They 
  were 
  then 
  transferred 
  to 
  a 
  large 
  quantity 
  of 
  

   the 
  fixing 
  fluid 
  and 
  allowed 
  to 
  harden. 
  

  

  The 
  most 
  successful 
  fixation 
  Avas 
  obtained 
  Avith 
  Hermann's 
  

   fluid, 
  in 
  which 
  the 
  specimens 
  were 
  allowed 
  to 
  remain 
  from 
  

   five 
  to 
  twelve 
  or 
  fourteen 
  hours. 
  The 
  shorter 
  time 
  gave 
  

   rather 
  better 
  results 
  for 
  the 
  epithelial 
  structures, 
  especially 
  

   the 
  nuchal 
  organ 
  and 
  lateral 
  sense-organs, 
  whilst 
  the 
  longer 
  

   time 
  was 
  rather 
  better 
  for 
  internal 
  parts. 
  

  

  