﻿292 
  W. 
  B 
  LAX 
  LAND 
  BKNHAM. 
  

  

  much 
  more 
  powerfully 
  than 
  the 
  nuclei 
  of 
  the 
  internal 
  

   epithelium.^ 
  

  

  A 
  comparison 
  of 
  the 
  apparatus 
  in 
  P. 
  beddardi 
  with 
  that 
  

   described 
  by 
  Beddard 
  for 
  P. 
  subterraneus 
  shows 
  a 
  close 
  

   general 
  agreement, 
  both 
  macroscopically 
  and 
  microscopically, 
  

   and, 
  apart 
  from 
  a 
  possible 
  error 
  in 
  interpreting 
  the 
  radia- 
  

   ting 
  muscles 
  within 
  the 
  atrial 
  sac, 
  the 
  most 
  striking 
  difference 
  

   is 
  the 
  absence 
  in 
  this 
  new 
  species 
  of 
  the 
  long, 
  much 
  convo- 
  

   luted, 
  and 
  very 
  narrow 
  portion 
  of 
  the 
  atrium 
  and 
  the 
  

   presence 
  of 
  a 
  more 
  pronounced 
  penis. 
  In 
  both 
  of 
  these 
  

   points 
  P. 
  beddardi 
  forms 
  an 
  interesting 
  intermediate 
  stage 
  

   betAveen 
  the 
  simple 
  conditions 
  of 
  P. 
  alb 
  us 
  and 
  the 
  more 
  

   elaborate 
  arrangement 
  of 
  P. 
  subterraneus, 
  with 
  P. 
  

   kerguelenensis 
  as 
  in 
  some 
  respects 
  a 
  link 
  Avith 
  the 
  former. 
  

  

  The 
  most 
  characteristic 
  thing 
  about 
  two 
  of 
  our 
  New 
  Zealand 
  

   species 
  is 
  the 
  presence 
  of 
  a 
  muscular 
  sac 
  enclosing 
  the 
  

   atrium 
  {i. 
  e. 
  the 
  common 
  duct 
  of 
  vas 
  deferens 
  and 
  spermi- 
  

   ducal 
  gland), 
  which 
  is 
  more 
  or 
  less 
  coiled 
  so 
  as 
  to 
  be 
  stowed 
  

   away 
  within 
  it. 
  No 
  trace 
  of 
  this 
  sac 
  exists 
  in 
  P. 
  kerguelen- 
  

   ensis, 
  but 
  the 
  spermiducal 
  gland 
  is 
  shorter 
  and 
  the 
  ''atrium" 
  

   is 
  much 
  longer 
  than 
  in 
  the 
  South 
  American 
  species, 
  and 
  is 
  

   moreover 
  glandular, 
  as 
  is 
  the 
  atrium 
  of 
  our 
  New 
  Zealand 
  

   forms. 
  The 
  absence 
  of 
  a 
  penis 
  in 
  the 
  Kerguelen 
  species 
  

   forbids 
  us 
  placing 
  it 
  as 
  a 
  direct 
  link. 
  But 
  if 
  Ave 
  start 
  with 
  

   P. 
  alb 
  us, 
  we 
  find 
  the 
  vas 
  deferens 
  opening 
  into 
  the 
  short, 
  

   narrow, 
  and 
  apparently 
  non-glandular 
  neck 
  of 
  a 
  small 
  spermi- 
  

   ducal 
  gland. 
  (The 
  gland 
  is 
  much 
  larger 
  and 
  coiled 
  in 
  

   P. 
  niger 
  and 
  in 
  P. 
  lacustris, 
  where 
  it 
  occupies 
  the 
  whole 
  

   length 
  of 
  its 
  segment). 
  The 
  common 
  duct 
  thus 
  formed 
  

   perforates 
  a 
  protrusible 
  penis, 
  contained 
  Avithin 
  a 
  compara- 
  

   tively 
  capacious 
  penial 
  sac. 
  The 
  next 
  stage, 
  apart 
  from 
  the 
  

   penis, 
  is 
  P. 
  kerguelenensis, 
  in 
  Avhich 
  the 
  coinmon 
  duct 
  

   (atrium) 
  is 
  longer 
  and 
  glandular. 
  Then 
  comes 
  an 
  entirely 
  

   new 
  structure, 
  and 
  Ave 
  have 
  the 
  stage 
  in 
  which 
  the 
  muscular 
  

   AA^all 
  becomes 
  separated 
  from 
  the 
  glandular 
  epithelium, 
  so 
  as 
  

  

  ' 
  Unfortunately 
  the 
  litliograj3her 
  has 
  made 
  the 
  nuclei 
  of 
  tiie 
  epidermic 
  cells 
  

   next 
  tiie 
  pore 
  round 
  instead 
  of 
  flat. 
  

  

  