﻿26 
  

  

  H. 
  S. 
  Pratt. 
  

  

  The 
  oviducts. 
  

  

  Is 
  lias 
  already 
  been 
  inentioned 
  tliat 
  the 
  oviducts 
  of 
  the 
  sheep-tick 
  

   are 
  veiy 
  highly 
  inodified 
  from 
  the 
  typical 
  condition. 
  Their 
  proximal 
  

   ends 
  are 
  fused 
  and 
  form 
  a 
  Single, 
  median 
  vessel 
  0,33 
  mm 
  long, 
  which 
  

   joins 
  the 
  uterus 
  a 
  trifle 
  posteriorly 
  to 
  the 
  latter's 
  anterior 
  end. 
  In 
  

   the 
  virginal 
  female 
  this 
  median 
  oviduct 
  lies 
  in 
  a 
  plane 
  perpendicular 
  

   to 
  that 
  of 
  the 
  uterus 
  (PL 
  II, 
  Fig. 
  3): 
  thus 
  it 
  has 
  a 
  dorso-ventral 
  position, 
  

   whereas 
  the 
  uterus 
  lies 
  parallel 
  to 
  the 
  ventral 
  abdominal 
  wall. 
  As 
  

   the 
  female 
  becomes 
  older, 
  however, 
  and 
  the 
  uterus 
  through 
  frequent 
  

   bearing 
  becomes 
  larger 
  and 
  longer, 
  the 
  proximal 
  end 
  of 
  the 
  median 
  

   oviduct 
  gets 
  carried 
  forward 
  so 
  that 
  its 
  original 
  perpendicular 
  position 
  

   is 
  lost 
  and 
  gives 
  way 
  to 
  one 
  in 
  which 
  the 
  median 
  oviduct 
  nieets 
  the 
  

   uterus 
  at 
  an 
  acute 
  angle 
  (PI. 
  II, 
  Fig. 
  2 
  med.ovi). 
  And 
  when 
  the 
  

   uterus 
  is 
  distended 
  to 
  its 
  greatest 
  extent 
  by 
  the 
  presence 
  in 
  it 
  of 
  a 
  

   large 
  larva 
  this 
  angle 
  becomes 
  almost 
  obliterated, 
  and 
  the 
  median 
  

   oviduct 
  is 
  brought 
  to 
  lie 
  directly 
  on 
  the 
  dorsal 
  wall 
  of 
  the 
  uterus. 
  

   The 
  short, 
  paired, 
  distal 
  ends 
  of 
  the 
  oviducts 
  join 
  the 
  median, 
  

   unpaired 
  portion 
  just 
  described 
  to 
  the 
  right 
  and 
  left 
  respectively 
  

   (PI. 
  II, 
  Fig. 
  2 
  pa.ovi). 
  These 
  are 
  very 
  short 
  and 
  vary 
  in 
  length 
  

   with 
  the 
  condition 
  of 
  the 
  ovary 
  as 
  will 
  be 
  explained 
  later, 
  and 
  each 
  

   bears 
  at 
  its 
  extremity 
  the 
  ovoid 
  ovary. 
  

  

  The 
  function 
  and 
  purpose 
  of 
  this 
  peculiar 
  fusing 
  of 
  the 
  proximal 
  

   ends 
  of 
  the 
  oviducts, 
  which, 
  so 
  far 
  as 
  I 
  know, 
  is 
  not 
  to 
  be 
  met 
  with 
  

   to 
  the 
  same 
  extent 
  outside 
  the 
  group 
  of 
  Pupipara, 
  is 
  to 
  provide 
  a 
  

   reservoir 
  for 
  the 
  sperm 
  of 
  the 
  male 
  animal 
  in 
  the 
  female, 
  in 
  other 
  

   words, 
  to 
  improvise 
  a 
  receptaculum 
  seminis. 
  The 
  sheeptick 
  has 
  no 
  

   receptaculum 
  seminis 
  of 
  the 
  form 
  usual 
  in 
  insects. 
  The 
  extreme 
  

   anterior 
  end 
  of 
  the 
  uterus, 
  which 
  appears 
  as 
  a 
  small 
  projection 
  in 
  

   front 
  of 
  the 
  point 
  of 
  juncture 
  of 
  the 
  median 
  oviduct 
  with 
  it, 
  mar 
  

   be 
  a 
  rudiment 
  which 
  is 
  homologous 
  to 
  the 
  receptaculum 
  seminis 
  of 
  

   other 
  insects, 
  and 
  has 
  been 
  so 
  interpreted 
  by 
  Leuckart 
  (10). 
  All 
  

   of 
  the 
  other 
  brachyceran 
  dipters, 
  so 
  far 
  as 
  I 
  know, 
  are 
  provided 
  

   with 
  a 
  receptaculum 
  seminis, 
  and 
  the 
  ancestors 
  of 
  Melophagus 
  and 
  

   the 
  other 
  pupipars 
  were 
  undoubtedly 
  no 
  exception 
  to 
  the 
  rule, 
  But 
  

   probably 
  the 
  enormous 
  distention 
  of 
  the 
  uterin 
  e 
  wall, 
  which 
  has 
  

   resulted 
  from 
  the 
  retention 
  of 
  the 
  growing 
  larva 
  in 
  the 
  uterus, 
  has 
  

   led 
  to 
  the 
  extinction 
  of 
  the 
  receptaculum 
  seminis 
  as 
  a 
  fimctional 
  

   organ. 
  Its 
  place, 
  then, 
  is 
  taken 
  by 
  the 
  fused 
  ends 
  of 
  the 
  oviducts; 
  

   this 
  acts 
  as 
  a 
  receptacle 
  of 
  semen 
  and 
  is 
  constantly 
  filled 
  with 
  it. 
  

  

  