﻿400 
  Mr. 
  Frederick 
  Muir 
  on 
  the 
  Male 
  Abdominal 
  

  

  eighth 
  segment 
  is 
  attached 
  to 
  the 
  seventh 
  by 
  a 
  large 
  

   membrane 
  {b) 
  and 
  can 
  be 
  completely 
  withdrawn 
  into 
  it. 
  

   The 
  ninth 
  segment 
  is 
  highly 
  modified 
  and 
  shaped 
  like 
  an 
  

   oat 
  (fig. 
  11). 
  The 
  distal 
  and 
  visible 
  portion 
  consists 
  of 
  a 
  

   pair 
  of 
  pointed 
  and 
  slightly 
  curved 
  lobes 
  connected 
  in 
  a 
  

   V-shaped 
  piece 
  on 
  the 
  dorsal 
  aspect 
  ; 
  the 
  basal 
  and 
  internal 
  

   portion 
  consists 
  of 
  a 
  membranous 
  plate 
  (/) 
  chitinised 
  along 
  

   the 
  edges 
  (g). 
  On 
  the 
  ventral 
  aspect 
  at 
  the 
  meeting 
  of 
  

   the 
  lobes 
  there 
  is 
  a 
  small 
  trident 
  body 
  (figs. 
  6 
  and 
  10, 
  and 
  11 
  1) 
  

   attached 
  to 
  a 
  rod 
  (d) 
  which 
  lies 
  free 
  within 
  the 
  segment. 
  

   The 
  segment 
  is 
  attached 
  to 
  the 
  preceding 
  by 
  a 
  membrane 
  

   (c), 
  which 
  allows 
  of 
  considerable 
  play 
  between 
  the 
  pleural 
  

   plates 
  of 
  the 
  eighth 
  segment. 
  The 
  anus 
  (an) 
  opens 
  on 
  a 
  

   membrane 
  between 
  the 
  lobes 
  ; 
  the 
  rectum 
  can 
  be 
  protruded. 
  

   In 
  figure 
  9 
  it 
  is 
  shown 
  retracted 
  and 
  in 
  figures 
  7 
  and 
  11 
  

   protruded. 
  

  

  For 
  the 
  sake 
  of 
  those 
  who 
  may 
  not 
  be 
  acquainted 
  with 
  

   the 
  male 
  genitalia 
  of 
  the 
  Staphylinidae 
  it 
  may 
  be 
  stated 
  

   that 
  in 
  the 
  more 
  generalised 
  forms, 
  e.g. 
  Gyrophaena 
  ptdchella, 
  

   the 
  median 
  lobe 
  is 
  long, 
  cylindrical, 
  with 
  the 
  median 
  foramen 
  

   at 
  the 
  basal 
  extremity 
  and 
  the 
  median 
  orifice 
  at 
  the 
  other, 
  

   the 
  internal 
  sac 
  is 
  small 
  and 
  undifferentiated 
  and 
  the 
  

   tegminal 
  lobes 
  large. 
  The 
  line 
  of 
  specialisation 
  is 
  for 
  the 
  

   basal 
  portion 
  of 
  the 
  median 
  lobe 
  to 
  become 
  large 
  and 
  the 
  

   distal 
  portion 
  shorter, 
  the 
  median 
  foramen 
  to 
  move 
  along 
  

   the 
  medio-ventral 
  line 
  towards 
  the 
  median 
  orifice 
  till 
  they 
  

   are 
  separated 
  by 
  only 
  a 
  very 
  narrow 
  area 
  and 
  for 
  the 
  

   tegminal 
  lobes 
  to 
  be 
  greatly 
  reduced 
  ; 
  a 
  good 
  example 
  of 
  

   this 
  specialisation 
  is 
  found 
  in 
  XaniJioliniis 
  glabralus. 
  The 
  

   internal 
  sac 
  in 
  these 
  more 
  speciahsed 
  forms 
  is 
  large, 
  com- 
  

   plex 
  and 
  often 
  bears 
  a 
  highly 
  developed 
  armature. 
  In 
  these 
  

   forms 
  the 
  median 
  lobe 
  is 
  a 
  beautifully 
  adapted 
  bulb 
  for 
  the 
  

   evagination 
  of 
  the 
  internal 
  sac 
  by 
  blood 
  pressure. 
  The 
  

   ventral 
  aspect 
  is 
  highly 
  chitinised, 
  also 
  the 
  dorsal 
  aspect, 
  

   but 
  not 
  so 
  strongly 
  ; 
  a 
  band 
  of 
  membrane 
  connects 
  the 
  

   two 
  ; 
  muscles 
  attach 
  the 
  dorsal 
  surface 
  to 
  the 
  ventral 
  

   portion, 
  and 
  by 
  their 
  contraction 
  the 
  dorsal 
  surface 
  is 
  

   depressed 
  and 
  the 
  pressure 
  exerted 
  on 
  the 
  fluids 
  within 
  the 
  

   bulb 
  ejects 
  the 
  sac. 
  In 
  freshly 
  dissected 
  specimens 
  this 
  

   can 
  be 
  accomplished 
  artificially 
  by 
  slight 
  pressure 
  on 
  the 
  

   dorsal 
  surface 
  of 
  the 
  bulb.* 
  In 
  all 
  species 
  in 
  which 
  the 
  

   internal 
  sac 
  is 
  specialised 
  (and 
  they 
  include 
  the 
  largest 
  

  

  * 
  For 
  fuller 
  details 
  of 
  this 
  subject 
  the 
  reader 
  is 
  referred 
  to 
  Trans. 
  

   Ent. 
  See. 
  Lond. 
  1912, 
  pp. 
  477 
  et 
  seq. 
  

  

  