﻿290 
  W. 
  BLAXLAND 
  BENHAM. 
  

  

  iiig 
  fibres 
  previously 
  described 
  are 
  continuous 
  ; 
  these 
  fibres 
  

   take 
  an 
  obliquely 
  longitudinal 
  course. 
  

  

  The 
  atrium 
  has 
  the 
  above 
  structure 
  for 
  only 
  a 
  moiety, 
  

   though 
  the 
  greater 
  moiety, 
  of 
  its 
  course; 
  further 
  downwards, 
  

   towards 
  the 
  exterior, 
  its 
  epithelium 
  gradually 
  changes 
  in 
  

   character 
  (fig. 
  23). 
  The 
  cells 
  are 
  lower, 
  the 
  nuclei 
  oval 
  and 
  

   more 
  closely 
  placed 
  ; 
  there 
  are 
  no 
  cell 
  boundaries 
  recognis- 
  

   able, 
  but 
  the 
  extent 
  of 
  the 
  cell 
  is 
  indicated 
  by 
  the 
  undulations 
  

   of 
  the 
  cuticle. 
  The 
  cilia 
  are 
  now 
  absent, 
  and 
  the 
  cytoplasm 
  

   secretes 
  a 
  distinct 
  cuticle, 
  which 
  is 
  vertically 
  striated 
  — 
  a 
  fact 
  

   which 
  is 
  more 
  evident 
  when 
  this 
  cuticle 
  is 
  cut 
  rather 
  obliquely, 
  

   as 
  in 
  the 
  lower 
  half 
  of 
  the 
  figure. 
  

  

  Further, 
  as 
  the 
  duct 
  enlarges 
  the 
  lumen 
  is 
  consequently 
  

   wider 
  than 
  before. 
  This 
  widened 
  portion 
  terminates 
  some 
  

   little 
  distance 
  before 
  the 
  external 
  aperture 
  is 
  reached, 
  and 
  

   forms 
  a 
  short 
  though 
  evident 
  projection 
  into 
  the 
  terminal 
  

   region 
  of 
  the 
  atrial 
  sac; 
  this 
  projection 
  — 
  or 
  "penis," 
  as 
  it 
  

   may 
  be 
  termed 
  — 
  is 
  more 
  readily 
  seen 
  in 
  the 
  preparation 
  of 
  

   the 
  entire 
  apparatus 
  in 
  glycerine 
  than 
  in 
  trausverse 
  sections; 
  

   but, 
  being 
  aware 
  of 
  its 
  presence, 
  one 
  may 
  distinguish 
  it 
  even 
  

   in 
  transverse 
  sections. 
  

  

  The 
  structure 
  of 
  this 
  penis 
  is 
  best 
  understood 
  by 
  the 
  study 
  

   of 
  the 
  isolated 
  apparatus 
  (fig. 
  17). 
  The 
  atrium, 
  now 
  a 
  very 
  

   narrow 
  tube, 
  perforates 
  a 
  short 
  truncated 
  cone, 
  whose 
  end 
  

   projects 
  into 
  a 
  more 
  capacious 
  chamber, 
  which 
  may 
  be 
  termed 
  

   the 
  " 
  penial 
  sac"; 
  at 
  the 
  end 
  of 
  the 
  cone 
  is 
  the 
  aperture 
  of 
  

   the 
  atrium 
  itself 
  (o. 
  p.). 
  The 
  wall 
  of 
  the 
  atrial 
  sac 
  is 
  seen 
  to 
  

   be 
  continuous 
  with 
  the 
  base 
  of 
  the 
  peuial 
  sac. 
  

  

  This 
  figure 
  may 
  be 
  compared 
  with 
  Beddard's 
  figure 
  30, 
  

   which 
  represents 
  a 
  longitudinal 
  section 
  at 
  a 
  point 
  " 
  some 
  

   distance 
  from 
  the 
  external 
  orifice 
  of 
  the 
  atrium," 
  where 
  

   " 
  the 
  muscular 
  and 
  peritoneal 
  coats 
  become 
  widely 
  separated 
  

   from 
  the 
  epithelial 
  layer. 
  At 
  this 
  point 
  the 
  lumen 
  of 
  the 
  

   atrium 
  becomes 
  suddenly 
  contracted." 
  I 
  think 
  that 
  these 
  

   sudden 
  changes 
  in 
  character 
  of 
  lumen 
  and 
  relation 
  of 
  the 
  

   coats 
  of 
  the 
  organ 
  in 
  P. 
  subterraueus 
  represent 
  a 
  small 
  — 
  

   possibly 
  vestigial, 
  or 
  equally 
  possibly 
  a 
  nascent 
  — 
  penis. 
  

  

  