﻿SOMIi; 
  Nl'JW 
  SI'KCIBS 
  OF 
  THE 
  GENUS 
  I'HREODRILUS. 
  275 
  

  

  In 
  P. 
  alb 
  us 
  the 
  single 
  uephridium 
  in 
  each 
  side 
  extends 
  

   from 
  Segment 
  V 
  (in 
  which 
  the 
  funnel 
  lies) 
  to 
  Segment 
  X, 
  its 
  

   pore, 
  however, 
  being 
  in 
  Segment 
  VI. 
  In 
  P. 
  niger 
  it 
  

   extends 
  fi*om 
  VII 
  to 
  IX, 
  and 
  in 
  P. 
  kerguelenensis 
  from 
  

   VII 
  to 
  X. 
  It 
  is 
  probable, 
  therefore, 
  that 
  in 
  this 
  new 
  species 
  

   — 
  P. 
  lacustris 
  — 
  the 
  pregenital 
  nephridium 
  has 
  the 
  same 
  

   disposition 
  as 
  in 
  the 
  last-named 
  species. 
  

  

  R 
  ep 
  rod 
  lie 
  tive 
  System 
  . 
  — 
  Of 
  the 
  fairly 
  numerous 
  indi- 
  

   viduals 
  obtained, 
  only 
  three 
  turned 
  out 
  to 
  be 
  sexually 
  mature. 
  

   One 
  of 
  these 
  was 
  mounted 
  entire, 
  a 
  second 
  was 
  cut 
  into 
  

   longitudinal 
  sections, 
  and 
  the 
  third 
  was 
  dissected 
  notwith- 
  

   standing 
  its 
  small 
  size; 
  it 
  was 
  bisected 
  in 
  the 
  region 
  of 
  the 
  

   reproductive 
  organs, 
  and 
  the 
  latter 
  were 
  partially 
  isolated 
  by 
  

   removal, 
  under 
  a 
  dissecting 
  lens, 
  of 
  the 
  gut 
  and 
  part 
  of 
  the 
  

   body-wall, 
  so 
  that 
  the 
  true 
  form 
  and 
  disposition 
  of 
  the 
  

   spermiducal 
  gland 
  could 
  be 
  studied. 
  In 
  this 
  way 
  a 
  check 
  on 
  

   the 
  longitudinal 
  sections 
  was 
  obtained, 
  and 
  a 
  very 
  necessary 
  

   check 
  in 
  the 
  case 
  of 
  an 
  organ, 
  serial 
  sections 
  of 
  which 
  had 
  to 
  

   be 
  studied 
  under 
  very 
  high 
  powers. 
  

  

  The 
  single 
  pair 
  of 
  testes 
  lies 
  in 
  Segment 
  XI, 
  attached 
  to 
  

   the 
  anterior 
  wall. 
  Beddard, 
  in 
  his 
  account 
  of 
  P. 
  subter- 
  

   raneus, 
  emphasises 
  the 
  point 
  that 
  in 
  that 
  species 
  the 
  testes 
  

   extend 
  through 
  or 
  below 
  the 
  septum 
  into 
  the 
  preceding 
  

   segment. 
  However 
  that 
  may 
  be, 
  it 
  is 
  not 
  the 
  case 
  in 
  

   P. 
  lacustris, 
  nor, 
  as 
  Michaelsen 
  insists, 
  in 
  P. 
  kerguelen- 
  

   ensis. 
  An 
  explanation 
  of 
  the 
  condition 
  described 
  by 
  Bed- 
  

   dard 
  seems 
  to 
  be 
  that 
  the 
  septa 
  in 
  this 
  part 
  of 
  the 
  body 
  are 
  

   very 
  imperfect, 
  as 
  is 
  evidenced 
  by 
  the 
  presence 
  of 
  sperm- 
  

   morulte 
  and 
  bunches 
  of 
  developing 
  sperms 
  in 
  several 
  of 
  the 
  

   segments 
  preceding 
  the 
  eleventh. 
  I 
  find, 
  in 
  one 
  case, 
  that 
  

   Segments 
  VIII 
  and 
  IX 
  are 
  filled 
  with 
  sperms; 
  in 
  other 
  cases 
  

   the 
  coolom 
  of 
  Segments 
  X, 
  XI, 
  and 
  XII 
  is 
  similarly 
  occupied, 
  

   while 
  in 
  a 
  third 
  individual 
  even 
  Segment 
  VII 
  contains 
  a 
  

   few 
  of 
  these 
  developing 
  sperms. 
  There 
  are 
  no 
  sperm-sacs 
  ; 
  

   the 
  sperm-masses 
  are 
  free 
  in 
  the 
  coelom 
  in 
  Segments 
  VII 
  to 
  

   XII; 
  while 
  I 
  did 
  not 
  find 
  any 
  in 
  the 
  post-clitellar 
  segments 
  

   It 
  is 
  interesting 
  to 
  recall 
  that 
  also 
  in 
  P. 
  kerguelenensis 
  

  

  