﻿86 
  B. 
  J. 
  ALLEN. 
  

  

  bright 
  scarlet 
  to 
  deep 
  purple-red 
  according 
  to 
  the 
  degree 
  of 
  

   aeration 
  of 
  the 
  blood, 
  which, 
  showing 
  through 
  the 
  transparent 
  

   body-Avalls, 
  gives 
  its 
  own 
  colour 
  to 
  this 
  region 
  (see 
  p. 
  126). 
  

   The 
  parapodia 
  and 
  their 
  cirri 
  are 
  here 
  almost 
  colourless. 
  

   The 
  posterior 
  part 
  of 
  the 
  body 
  is 
  black 
  or 
  dark 
  green 
  and 
  

   white, 
  the 
  dark 
  colour 
  being 
  due 
  to 
  pigment 
  in 
  the 
  cells 
  of 
  

   the 
  intestine; 
  the 
  white, 
  which 
  is 
  specially 
  marked 
  in 
  ripe 
  

   males, 
  to 
  the 
  genital 
  products. 
  

  

  The 
  head 
  is 
  small 
  and 
  hemispherical, 
  as 
  can 
  be 
  seen 
  from 
  

   the 
  dorsal 
  view 
  (PI. 
  7, 
  fig. 
  1, 
  and 
  PI. 
  8, 
  fig, 
  7) 
  and 
  from 
  the 
  

   ventral 
  view 
  (PL 
  8, 
  fig. 
  8). 
  It 
  is 
  provided 
  with 
  four 
  eyes, 
  

   two 
  small 
  dorsal 
  and 
  two 
  larger 
  ventral. 
  A 
  short 
  median 
  

   tentacle 
  has 
  its 
  origin 
  on 
  the 
  ventral 
  side 
  of 
  the 
  head, 
  being 
  

   placed 
  so 
  far 
  back 
  that 
  when 
  the 
  proboscis 
  is 
  completely 
  with- 
  

   drawn 
  into 
  the 
  body, 
  the 
  base 
  of 
  the 
  tentacle 
  also 
  comes 
  to 
  lie 
  

   actually 
  within 
  the 
  mouth 
  (PI. 
  8, 
  fig. 
  8). 
  The 
  tentacle, 
  which 
  

   is 
  covered 
  with 
  minute 
  papiliaj 
  (the 
  external 
  openings 
  of 
  

   epithelial 
  glands), 
  extends 
  for 
  a 
  short 
  distance 
  beyond 
  the 
  

   anterior 
  margin 
  of 
  the 
  head 
  (figs. 
  1 
  and 
  7). 
  As 
  will 
  be 
  

   shown 
  later, 
  the 
  single 
  median 
  tentacle 
  represents 
  two 
  lateral 
  

   tentacles 
  fused 
  together, 
  for 
  it 
  receives 
  two 
  nerves, 
  one 
  from 
  

   either 
  side 
  of 
  the 
  brain. 
  

  

  The 
  very 
  large 
  palps 
  (^^/p.) 
  arise 
  between 
  the 
  head 
  proper 
  

   and 
  the 
  parapodia 
  of 
  the 
  first 
  segment. 
  These 
  palps 
  are 
  

   capable 
  of 
  great 
  extension 
  (cf. 
  PI. 
  9, 
  fig-. 
  12), 
  and 
  may 
  attain 
  

   a 
  length 
  equal 
  to 
  at 
  least 
  half 
  the 
  length 
  of 
  the 
  body. 
  Their 
  

   general 
  appearance 
  can 
  be 
  seen 
  from 
  figs. 
  1 
  and 
  7. 
  They 
  are 
  

   horse-shoe 
  shaped 
  in 
  transverse 
  section, 
  are 
  richly 
  supplied 
  

   with 
  papilke, 
  and 
  a 
  crenated 
  membrane 
  runs 
  along 
  each 
  

   margin 
  of 
  the 
  flattened 
  side. 
  A 
  single 
  large 
  blood-vessel, 
  

   along 
  which 
  in 
  the 
  living 
  worm 
  a 
  constant 
  succession 
  of 
  

   strong 
  pulsations 
  is 
  seen 
  to 
  pass, 
  extends 
  through 
  nearly 
  the 
  

   whole 
  length 
  of 
  each 
  palp. 
  

  

  In 
  describing 
  the 
  habits 
  of 
  the 
  worm 
  it 
  was 
  stated 
  (p. 
  83) 
  

   that 
  when 
  the 
  worm 
  is 
  in 
  its 
  tube 
  the 
  palps 
  may 
  either 
  lie 
  

   straight 
  in 
  front 
  of 
  the 
  head, 
  being 
  often 
  protruded 
  out 
  of 
  the 
  

   mouth 
  of 
  the 
  tube, 
  or 
  they 
  may 
  be 
  formed 
  into 
  a 
  number 
  of 
  

  

  