﻿278 
  W. 
  BLAXLAND 
  BKNHAM. 
  

  

  external 
  pore 
  is 
  reached. 
  Protiusiou 
  of 
  the 
  penis 
  appears 
  to 
  

   be 
  effected 
  by 
  the 
  contraction 
  of 
  these 
  muscles. 
  

  

  In 
  comparing 
  this 
  apparatus 
  with 
  that 
  of 
  other 
  species 
  it 
  

   will 
  be 
  recognised 
  that 
  it 
  closely 
  agrees 
  with 
  that 
  of 
  

   P. 
  niger, 
  in 
  which 
  the 
  gland 
  occupies 
  the 
  whole 
  segment 
  

   and 
  pushes 
  back 
  the 
  hind 
  septum. 
  It 
  is 
  much 
  larger 
  than 
  

   that 
  of 
  P. 
  alb 
  us, 
  which 
  is 
  only 
  half 
  a 
  segment 
  long; 
  while 
  

   the 
  organ 
  in 
  P. 
  kerguelenen 
  sis 
  differs 
  from 
  all 
  these 
  in 
  

   that 
  the 
  sperm-duct 
  apparently 
  enters 
  the 
  spermiducal 
  gland 
  

   some 
  little 
  distance 
  from 
  the 
  free 
  end 
  ; 
  further, 
  this 
  species 
  is 
  

   without 
  a 
  penis; 
  at 
  any 
  rate, 
  Michaelsen 
  neither 
  describes 
  nor 
  

   figures 
  any 
  such 
  a 
  termination 
  to 
  the 
  atrium. 
  But 
  the 
  South 
  

   American 
  species 
  are 
  provided 
  with 
  a 
  protrusible 
  organ^ 
  and 
  

   agree 
  in 
  this 
  matter 
  precisely 
  with 
  P. 
  lacustris. 
  

  

  The 
  ovary 
  lies 
  in 
  Segment 
  XII, 
  alongside 
  of 
  and 
  partially 
  

   embraced 
  by 
  the 
  coils 
  of 
  the 
  spermiducal 
  gland 
  ; 
  the 
  oviduct 
  

   has 
  the 
  normal 
  structure. 
  In 
  one 
  specimen 
  I 
  noted 
  ova 
  in 
  

   Segments 
  XV 
  and 
  XVI, 
  but 
  did 
  not 
  detect 
  any 
  ovisacs. 
  

  

  The 
  spermatheca 
  (figs. 
  8, 
  9, 
  10) 
  is 
  an 
  elongated 
  organ, 
  

   and, 
  as 
  in 
  P. 
  albus 
  and 
  others, 
  is 
  differentiated 
  into 
  three 
  

   regions, 
  though 
  they 
  are 
  not 
  so 
  sharply 
  marked 
  as 
  in 
  that 
  

   species. 
  The 
  external 
  pore 
  in 
  Segment 
  XIII, 
  on 
  the 
  ventral 
  

   surface, 
  leads 
  into 
  a 
  narrow 
  duct 
  (a) 
  with 
  a 
  muscular 
  coat; 
  it 
  

   is 
  only 
  slightly 
  dilated 
  at 
  the 
  entrance 
  — 
  in 
  contrast 
  with 
  

   P. 
  kerguelenensis 
  and 
  others, 
  — 
  and 
  soon 
  narrows; 
  the 
  

   muscular 
  coat 
  is 
  longitudinal, 
  and 
  I 
  did 
  not 
  detect 
  any 
  

   circular 
  fibres 
  in 
  the 
  first 
  part 
  of 
  the 
  duct, 
  which 
  takes 
  a 
  

   vertical 
  direction 
  obliquely 
  backwards 
  towards 
  the 
  hinder 
  

   septum 
  ; 
  it 
  then 
  bends 
  abruptly 
  upon 
  itself, 
  and 
  here 
  circular 
  

   muscles 
  appear 
  and 
  the 
  longitudinal 
  muscle-fibres 
  pass 
  

   onwards 
  beyond 
  the 
  bend, 
  to 
  be 
  inserted 
  in 
  the 
  body-wall 
  (see 
  

   fig. 
  10, 
  Im.). 
  This 
  second 
  region 
  of 
  the 
  muscular 
  duct 
  {a'.), 
  

   after 
  a 
  short 
  course 
  parallel 
  to 
  its 
  former 
  course, 
  bends 
  back- 
  

   wards 
  and 
  downwai'ds 
  towards 
  the 
  lower 
  part 
  of 
  the 
  septum 
  

   (XIII, 
  XIV), 
  and 
  passes 
  through 
  the 
  septum 
  and 
  becomes 
  the 
  

   second 
  region 
  {h.) 
  — 
  the 
  muscular 
  coat 
  is 
  here 
  absent, 
  the 
  

   epithelium 
  becomes 
  lower 
  and 
  appears 
  to 
  be 
  glandular, 
  as 
  the 
  

  

  