﻿Reproductive 
  organs 
  of 
  Taenia 
  pisiformis. 
  371 
  

  

  existence 
  of 
  an 
  epithelium 
  as 
  noted 
  above 
  in 
  connection 
  with 
  other 
  

   organs. 
  Some 
  authors 
  deny, 
  others 
  maintain 
  its 
  existence, 
  while 
  

   still 
  others 
  admit 
  its 
  existence 
  in 
  early 
  stages 
  but 
  deny 
  it 
  in 
  later 
  

   ones. 
  An 
  explanation 
  of 
  these 
  differences 
  similar 
  to 
  that 
  above 
  

   given 
  may 
  be 
  made 
  here. 
  In 
  Taenia 
  pisiformis 
  I 
  find 
  an 
  epithelium 
  

   present 
  at 
  all 
  stages, 
  altho 
  not 
  so 
  distinctly 
  differentiated 
  as 
  in 
  the 
  

   oviduct 
  and 
  yolk 
  duct. 
  

  

  The 
  vas 
  a 
  efferentia 
  are 
  the 
  last 
  of 
  the 
  ducts 
  to 
  develop. 
  

   Shortly 
  after 
  the 
  appearance 
  of 
  the 
  testes 
  slender 
  branching 
  cords 
  

   are 
  seen 
  among 
  the 
  latter. 
  These 
  cords 
  consist 
  of 
  elongated 
  cells 
  

   with 
  fibrous 
  cytoplasm, 
  and 
  in 
  most 
  cases 
  (but 
  not 
  all) 
  probably 
  

   arise 
  in 
  direct 
  continuity 
  with 
  the 
  testes 
  (Fig. 
  42). 
  In 
  any 
  case 
  they 
  

   are 
  connected 
  to 
  these 
  at 
  an 
  early 
  stage. 
  Later 
  the 
  different 
  ducts 
  

   unite 
  with 
  one 
  another 
  ^), 
  and 
  finally 
  growing 
  out 
  unite 
  with 
  the 
  

   vas 
  deferens. 
  The 
  cells 
  composing 
  these 
  ducts 
  are 
  in 
  direct 
  con- 
  

   nection 
  with 
  the 
  parenchyma 
  fibres 
  and 
  evidently 
  are 
  modified 
  paren- 
  

   chyma 
  cells. 
  Soon 
  a 
  lumen 
  appears 
  and 
  a 
  basement 
  membrane 
  

   arises 
  peripherally.^) 
  The 
  origin 
  of 
  this 
  membrane 
  is 
  uncertain 
  — 
  

   whether 
  from 
  the 
  anläge 
  itself 
  or 
  from 
  the 
  surrounding 
  parenchyma. 
  

   Since 
  the 
  former 
  is 
  primarily 
  a 
  part 
  of 
  the 
  latter 
  however 
  the 
  

   question 
  is 
  of 
  but 
  minor 
  importance. 
  Apparently 
  the 
  lumen 
  of 
  the 
  

   duct 
  arises 
  as 
  a 
  split 
  in 
  the 
  syncytium 
  of 
  the 
  anläge, 
  as 
  the 
  duct 
  

   enlarges 
  with 
  the 
  appearance 
  of 
  its 
  lumen, 
  and 
  the 
  cells 
  composing 
  

   its 
  w^'ills 
  now 
  form 
  a 
  thin 
  epithelium 
  bounding 
  the 
  latter 
  and 
  resting 
  

   upon 
  the 
  basement 
  membrane, 
  which 
  is 
  protruded 
  at 
  intervals 
  by 
  

   their 
  nuclei. 
  I 
  find 
  no 
  evidence 
  of 
  any 
  absorption 
  or 
  degeneration 
  

   in 
  the 
  syncytium 
  to 
  form 
  the 
  lumen 
  of 
  the 
  ducts. 
  With 
  further 
  

   development 
  the 
  epithelium 
  becomes 
  much 
  thinner 
  and 
  so 
  closel}^ 
  

   fused 
  with 
  the 
  basement 
  membrane 
  that 
  a 
  distinction 
  is 
  impossible. 
  

   The 
  nuclei 
  remain 
  as 
  spindle-shaped 
  protuberances 
  of 
  the 
  wall 
  from 
  

   point 
  to 
  point 
  (Fig. 
  29). 
  Where 
  the 
  ducts 
  join 
  the 
  testes 
  their 
  thin 
  

   epithelial 
  wall 
  becomes 
  continuous 
  with 
  the 
  membrane 
  of 
  the 
  latter, 
  

   where 
  they 
  join 
  the 
  vas 
  deferens 
  their 
  epithelium 
  merges 
  with 
  the 
  

   epithelium 
  of 
  this 
  duct. 
  

  

  A 
  consideration 
  of 
  the 
  epithelial 
  question 
  and 
  its 
  relation 
  to 
  

  

  1) 
  Some 
  neighboring 
  ducts 
  are 
  united 
  at 
  a 
  very 
  early 
  stage, 
  possibly 
  

   from 
  the 
  first. 
  

  

  2) 
  The 
  formation 
  of 
  the 
  latter 
  usually 
  at 
  least 
  precedes 
  that 
  of 
  the 
  

   lumen. 
  

  

  