﻿176 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol. 
  103 
  

  

  the 
  copiilatory 
  bursa 
  (bd). 
  No 
  common 
  atrium 
  is 
  present, 
  

   and 
  both 
  the 
  papUla 
  of 
  the 
  penis 
  and 
  the 
  opening 
  of 
  the 
  

   oviduct 
  are 
  situated 
  in 
  the 
  "male" 
  atrium. 
  The 
  atrium 
  is 
  a 
  conical 
  

   cavity, 
  wide 
  anteriorly 
  and 
  tapering 
  toward 
  the 
  genital 
  pore. 
  It 
  is 
  

   lined 
  with 
  a 
  cubical 
  epithelium, 
  below 
  which 
  occurs 
  a 
  thin 
  layer 
  of 
  

   fine 
  circular 
  muscle 
  fibers 
  and 
  a 
  thicker 
  layer 
  of 
  coarser 
  longitudinal 
  

   fibers. 
  

  

  The 
  penis 
  consists 
  of 
  a 
  spherical, 
  muscular 
  bulb 
  and 
  an 
  elongated 
  

   papilla. 
  The 
  penis 
  bulb 
  is 
  differentiated 
  into 
  a 
  wide 
  peripheral 
  

   muscular 
  zone 
  and 
  a 
  more 
  central 
  parenchymatic 
  zone 
  which 
  contains 
  

   a 
  cavity, 
  the 
  seminal 
  vesicle 
  (vs) 
  . 
  The 
  vesicle 
  is 
  lined 
  with 
  a 
  glandu- 
  

   lar 
  epithelium 
  and 
  its 
  wall 
  forms 
  villuslike 
  projections. 
  The 
  two 
  

   vasa 
  deferentia 
  (vd) 
  penetrate 
  the 
  penis 
  bulb 
  from 
  the 
  anterolateral 
  

   sides 
  and 
  open 
  into 
  the 
  seminal 
  vesicle 
  on 
  two 
  prominent 
  conical 
  

   papillae 
  projecting 
  from 
  the 
  anterior 
  wall 
  of 
  the 
  vesicle 
  a 
  short 
  dis- 
  

   tance 
  from 
  each 
  other. 
  

  

  The 
  papilla 
  of 
  the 
  penis 
  is 
  finger-shaped, 
  tapering 
  toward 
  the 
  tip, 
  

   and 
  is 
  highly 
  muscular. 
  It 
  is 
  covered 
  with 
  a 
  thin 
  cubical 
  epithelium. 
  

   Below 
  the 
  epithelium 
  there 
  is, 
  in 
  the 
  basal 
  portion 
  of 
  the 
  papilla, 
  a 
  

   thin 
  layer 
  of 
  longitudinal 
  muscles, 
  below 
  which 
  lie 
  a 
  stronger 
  circular 
  

   layer 
  and 
  a 
  second 
  longitudinal 
  layer. 
  In 
  the 
  distal 
  part 
  of 
  the 
  

   papUla, 
  the 
  external 
  longitudinal 
  layer 
  is 
  lacking. 
  The 
  axis 
  of 
  the 
  

   papilla 
  is 
  pierced 
  by 
  the 
  ejaculatory 
  duct 
  (de) 
  which 
  leads 
  from 
  the 
  

   seminal 
  vesicle 
  to 
  the 
  tip 
  of 
  the 
  papilla. 
  The 
  duct 
  has 
  a 
  cubical 
  

   epithelium 
  and 
  a 
  strong 
  coat 
  of 
  longitudinal 
  muscle 
  fibers. 
  

  

  The 
  two 
  oviducts 
  approach 
  the 
  midline 
  in 
  the 
  region 
  of 
  the 
  copula- 
  

   tory 
  apparatus, 
  the 
  right 
  one 
  passing 
  between 
  the 
  atrium 
  and 
  the 
  

   bursa 
  stalk, 
  and 
  unite 
  behind 
  and 
  above 
  the 
  atrium. 
  The 
  common 
  

   oviduct 
  (ode) 
  proceeds 
  ventrally, 
  then 
  curves 
  anteriorly, 
  and 
  empties 
  

   into 
  the 
  terminal 
  part 
  of 
  the 
  atrium 
  close 
  to 
  the 
  genital 
  pore. 
  

  

  The 
  copulatory 
  bm-sa 
  (b) 
  is 
  a 
  lobed 
  sac 
  lined 
  with 
  a 
  tall 
  glandular 
  

   epithelium. 
  The 
  distal 
  parts 
  of 
  the 
  epithelial 
  cells 
  are 
  filled 
  with 
  

   fine 
  eosinophilic 
  granules. 
  The 
  duct 
  or 
  stalk 
  of 
  the 
  bursa 
  (bd) 
  is 
  dif- 
  

   ferentiated 
  into 
  a 
  narrow 
  anterior 
  section 
  with 
  a 
  weak 
  muscular 
  coat, 
  

   which 
  connects 
  with 
  the 
  bursa, 
  and 
  a 
  posterior 
  wider 
  section 
  which 
  

   bends 
  ventrally 
  and 
  opens 
  at 
  the 
  genital 
  pore. 
  The 
  ceUs 
  of 
  the 
  

   anterior 
  section 
  resemble 
  those 
  of 
  the 
  bursa 
  in 
  having 
  similar 
  granular 
  

   inclusions. 
  Those 
  of 
  the 
  posterior 
  section 
  lack 
  the 
  inclusions 
  and 
  are 
  

   ciliated. 
  The 
  muscle 
  coat 
  of 
  the 
  duct 
  consists 
  of 
  intermingled 
  longi- 
  

   tudinal 
  and 
  circular 
  fibers. 
  

  

  Taxonomic 
  position. 
  — 
  I 
  have 
  placed 
  the 
  species 
  in 
  the 
  genus 
  

   Dendrocoelopsis 
  established 
  originally 
  for 
  a 
  European 
  species, 
  D. 
  

   spinosipenis 
  (Kenk). 
  The 
  original 
  definition 
  of 
  the 
  genus 
  was 
  based 
  

   on 
  the 
  following 
  characters: 
  fibers 
  of 
  the 
  inner 
  muscle 
  zone 
  of 
  the 
  

  

  