﻿THK 
  ANATOMY 
  OF 
  rCECIliOOH/JCTUS, 
  OI-APAHEDE. 
  123 
  

  

  The 
  opitheliuin 
  of 
  tlie 
  intestine 
  in 
  the 
  po.^terior 
  region 
  of 
  

   the 
  body 
  (rectum) 
  differs 
  only 
  from 
  tliat 
  already 
  desci'ibed 
  

   for 
  the 
  intestine 
  in 
  the 
  fact 
  that 
  all 
  the 
  cells 
  are 
  ciliated, 
  the 
  

   cilia 
  being 
  veiy 
  long. 
  The 
  action 
  of 
  these 
  cilia 
  can 
  be 
  clearly 
  

   seen 
  in 
  the 
  living 
  worm. 
  

  

  Body-cavit}^. 
  

  

  The 
  well-marked 
  segmentation 
  of 
  the 
  body 
  seen 
  externnlly 
  

   is 
  equall}^ 
  distinct 
  internally, 
  each 
  segment 
  being 
  separated 
  

   from 
  that 
  which 
  follows 
  it 
  by 
  a 
  transverse 
  septiiui. 
  The 
  

   septa, 
  the 
  first 
  of 
  which 
  lies 
  between 
  the 
  first 
  and 
  second 
  

   segments, 
  appear 
  to 
  divide 
  tlie 
  bodj'-cavity 
  into 
  a 
  number 
  of 
  

   separate 
  compartments, 
  between 
  which 
  no 
  communication 
  

   can 
  be 
  shown 
  to 
  exist. 
  These 
  compartments 
  are 
  not, 
  how- 
  

   ever, 
  of 
  equal 
  size, 
  for 
  in 
  the 
  region 
  occupied 
  by 
  the 
  muscular 
  

   pharynx 
  the 
  septa, 
  instead 
  of 
  lying 
  in 
  a 
  vertical 
  plane 
  cor- 
  

   responding 
  to 
  that 
  of 
  the 
  external 
  segmentation 
  of 
  the 
  body, 
  

   are 
  })ushed 
  backwards 
  for 
  a 
  considerable 
  distance. 
  This 
  

   pushing 
  backwards 
  of 
  the 
  septa, 
  which 
  is 
  shown 
  in 
  tlie 
  sagittal 
  

   section 
  represented 
  in 
  fig. 
  47 
  (PI. 
  11) 
  and 
  in 
  the 
  horizontal 
  

   section 
  fig. 
  43, 
  commences 
  with 
  the 
  septum 
  at 
  the 
  posterior 
  

   end 
  of 
  segment 
  5, 
  reaches 
  a 
  maximum 
  in 
  segment 
  8, 
  and 
  

   is 
  still 
  obvious 
  in 
  segment 
  12. 
  The 
  posterior 
  septa 
  of 
  

   segments 
  8, 
  9, 
  10, 
  and 
  11 
  all 
  extend 
  back 
  to 
  the 
  region, 
  

   which 
  external 
  segmentation 
  indicates 
  as 
  segment 
  12, 
  and 
  

   that 
  of 
  segment 
  12 
  is 
  pushed 
  back 
  into 
  13. 
  The 
  septa 
  of 
  

   segment 
  8 
  to 
  11 
  join 
  the 
  alimentary 
  canal 
  immediately 
  behind 
  

   the 
  point 
  where 
  the 
  pharynx 
  passes 
  into 
  the 
  intestine 
  (fig. 
  

   43, 
  v.). 
  These 
  septa 
  are 
  also 
  noteworthy 
  from 
  the 
  fact 
  that 
  

   the 
  muscle-fibres, 
  which 
  are 
  present 
  to 
  a 
  considerable 
  extent 
  

   in 
  the 
  septa 
  of 
  most 
  of 
  the 
  segments 
  of 
  the 
  body, 
  are 
  here 
  

   developed 
  to 
  a 
  very 
  remarkable 
  extent, 
  so 
  that 
  septa 
  8 
  to 
  

   11 
  have 
  become 
  highly 
  muscular 
  organs. 
  This 
  muscular 
  

   character 
  of 
  the 
  septa, 
  combined 
  with 
  the 
  manner 
  in 
  which 
  

   they 
  are 
  pushed 
  backwards, 
  seems 
  to 
  suggest 
  that 
  they 
  are 
  

   concerned 
  with 
  the 
  protrusion 
  of 
  the 
  anterior 
  portion 
  of 
  the 
  

   alimentary 
  canal 
  in 
  the 
  form 
  of 
  a 
  proboscis, 
  and 
  probably 
  

  

  