﻿Mr. 
  F. 
  Muir 
  07i 
  the 
  Male 
  Genital 
  Tube 
  in 
  Coleoptera. 
  405 
  

  

  is 
  the 
  apical 
  margin, 
  and 
  the 
  anterior 
  margin 
  of 
  an 
  abdo- 
  

   minal 
  segment 
  the 
  basal 
  margin. 
  It 
  is, 
  however, 
  not 
  a 
  good 
  

   principle 
  to 
  use 
  the 
  terms 
  anterior 
  or 
  posterior 
  when 
  

   discussing 
  parts 
  of 
  an 
  appendage. 
  

  

  The 
  term 
  invagination 
  is 
  applied 
  to 
  any 
  withdrawal 
  of 
  

   the 
  ectodermal 
  surface 
  into 
  the 
  body 
  lumen, 
  whether 
  it 
  be 
  

   long 
  and 
  narrow, 
  as 
  is 
  the 
  case 
  with 
  the 
  median 
  struts 
  in 
  

   many 
  beetles, 
  or 
  broad 
  and 
  short,, 
  as 
  is 
  the 
  case 
  with 
  a 
  

   large 
  portion 
  of 
  the 
  basal 
  piece 
  in 
  many 
  beetles. 
  

  

  Relation 
  of 
  Structure 
  and 
  Function. 
  

  

  A 
  study 
  of 
  the 
  skeleton, 
  that 
  is, 
  of 
  the 
  membrane 
  and 
  

   the 
  external 
  and 
  internal 
  chitinisations 
  of 
  the 
  male 
  genital 
  

   tube 
  of 
  Coleoptera, 
  shows 
  that 
  there 
  are 
  several 
  distinct 
  

   types 
  which 
  it 
  is 
  reasonable 
  to 
  expect 
  function 
  in 
  different 
  

   ways, 
  though 
  little 
  is 
  known 
  as 
  to 
  the 
  method 
  by 
  which 
  the 
  

   sperm 
  is 
  conveyed 
  from 
  the 
  testes 
  to 
  the 
  spermatheca. 
  

   One 
  of 
  the 
  most 
  interesting 
  and 
  instructive 
  works 
  on 
  this 
  

   subject 
  is 
  by 
  Blunck 
  on 
  Dytiscus 
  marginalis* 
  He 
  shows 
  

   the 
  formation 
  of 
  a 
  spermatophore 
  within 
  the 
  median 
  lobe 
  

   and 
  the 
  subsequent 
  transference 
  of 
  the 
  sperm 
  to 
  the 
  female 
  

   through 
  a 
  hole 
  in 
  the 
  wall 
  of 
  the 
  spermatophore. 
  The 
  

   median 
  lobe 
  of 
  the 
  Dytiscidae 
  is 
  funnel-shape, 
  and 
  there 
  

   is 
  no 
  specialised 
  internal 
  sac 
  ; 
  the 
  Haliplidae 
  and 
  Pelobiidae 
  

   are 
  built 
  on 
  a 
  similar 
  plan, 
  and 
  there 
  is 
  good 
  reason 
  to 
  

   believe 
  that 
  they 
  form 
  spermatophores 
  in 
  a 
  similar 
  manner 
  

   to 
  Dytiscus. 
  The 
  median 
  lobe 
  of 
  the 
  Gyrinidae 
  is 
  not 
  

   funnel-shape, 
  and 
  it 
  is 
  highly 
  probable 
  that 
  they 
  do 
  not 
  

   form 
  spermatophores, 
  or 
  if 
  they 
  do 
  they 
  are 
  of 
  a 
  different 
  

   shape 
  to 
  that 
  of 
  Dytiscus. 
  These 
  three 
  families 
  belong 
  to 
  

   the 
  minor 
  section 
  of 
  the 
  Coleoptera, 
  which 
  has 
  no 
  specialised 
  

   sac, 
  whereas 
  the 
  major 
  section 
  has 
  a 
  large, 
  more 
  or 
  less 
  

   highly 
  speciaUsed 
  sac, 
  which 
  is 
  the 
  chief 
  organ 
  of 
  copulation. 
  

   The 
  shape 
  of 
  the 
  sac 
  and 
  the 
  armature 
  upon 
  it 
  is 
  often 
  highly 
  

   complex, 
  especially 
  the 
  armature, 
  called 
  the 
  transfer 
  

   apparatus, 
  round 
  the 
  functional 
  orifice, 
  where 
  the 
  ejacu- 
  

   latory 
  duct 
  opens 
  on 
  the 
  internal 
  sac. 
  In 
  some 
  species 
  

   this 
  transfer 
  apparatus 
  takes 
  the 
  shape 
  of 
  a 
  fine, 
  long 
  tube 
  

   or 
  flagellum. 
  This 
  is 
  the 
  case 
  with 
  the 
  little 
  Cucujid 
  

   Cryptomorpha 
  desjardinsi, 
  which 
  has 
  a 
  long 
  sac 
  and 
  a 
  long, 
  

   slender 
  flagellum 
  ; 
  during 
  copulation 
  the 
  long 
  sac 
  is 
  entirely 
  

   everted 
  and 
  enters 
  the 
  long 
  membranous 
  vagina, 
  and 
  the 
  

  

  * 
  Zs. 
  wiss. 
  Zool. 
  Leipzig, 
  Bd. 
  cii, 
  Heft 
  2, 
  pp. 
  169-248 
  (1912); 
  

   also 
  Carl 
  Demandt, 
  t.c. 
  Bd. 
  ciii, 
  pp. 
  171-299 
  (1912) 
  for 
  the 
  muscles. 
  

  

  