﻿376 
  R- 
  T. 
  Young, 
  

  

  chalk 
  body 
  (Fig. 
  41). 
  Here 
  as 
  there 
  two 
  parenchyma 
  cells 
  may 
  enclose 
  

   a 
  developing 
  testis 
  (Fig. 
  39.)^) 
  The 
  fibrils 
  of 
  the 
  parent 
  cell 
  form 
  the 
  

   membrane 
  of 
  the 
  young 
  testis, 
  which 
  is 
  in 
  more 
  or 
  less 
  intimate 
  

   connection 
  with 
  the 
  surrounding 
  parenchyma 
  strands, 
  and 
  during 
  

   development 
  doubtless 
  adds 
  some 
  of 
  these 
  to 
  itself 
  Any 
  such 
  addi- 
  

   tion 
  however 
  is 
  mainly 
  offset 
  by 
  the 
  distension 
  of 
  the 
  membrane 
  as 
  

   the 
  gland 
  enlarges, 
  so 
  that 
  it 
  remains 
  very 
  thin 
  and 
  incomplete. 
  

   No 
  epithelium 
  is 
  here 
  present 
  the 
  spermatozoa 
  being 
  of 
  parenchymal 
  

   rather 
  than 
  epithelial 
  origin 
  (Figs. 
  35, 
  36, 
  39-42 
  and 
  54). 
  

  

  This 
  account 
  of 
  the 
  development 
  of 
  the 
  testis 
  membrane 
  varies 
  

   somewhat 
  from 
  that 
  given 
  by 
  Child 
  (1907, 
  II), 
  in 
  that 
  according 
  to 
  

   his 
  view 
  certain 
  parenchyma 
  cells 
  secrete 
  the 
  membrane, 
  while 
  in 
  

   my 
  opinion 
  it 
  is 
  formed 
  from 
  préexistent 
  parenchyma 
  strands, 
  those 
  

   cells 
  occurring 
  in 
  it 
  being 
  either 
  the 
  parent 
  cells 
  or 
  those 
  which 
  

   happen 
  to 
  lie 
  near 
  the 
  enlarging 
  testis. 
  With 
  increase 
  in 
  size 
  of 
  the 
  

   latter 
  the 
  membrane 
  later 
  becomes 
  much 
  distended, 
  which 
  would 
  

   account 
  for 
  the 
  rarity 
  of 
  membrane 
  nuclei 
  attributed 
  by 
  Child 
  to 
  

   their 
  degeneration. 
  

  

  Most 
  authors 
  ascribe 
  a 
  delicate 
  membrane 
  to 
  the 
  testis, 
  altho 
  its 
  

   presence 
  is 
  denied 
  by 
  some 
  of 
  the 
  earlier 
  writers 
  — 
  Salensky 
  (1874) 
  

   in 
  Amphilina, 
  Sommer 
  & 
  Landois 
  (1872) 
  in 
  BothriocepJiahis 
  latus, 
  and 
  

   MoNiEz 
  (1881) 
  in 
  Ligtila. 
  Considerable 
  difference 
  of 
  opinion 
  exists 
  

   regarding 
  the 
  structure 
  of 
  the 
  testis 
  membrane 
  and 
  the 
  wall 
  of 
  the 
  

   vas 
  efferens 
  continuous 
  therewith. 
  According 
  to 
  Kraemer 
  (1892) 
  in 
  

   Taenia 
  tondosa 
  and 
  Lönnberg 
  (1891) 
  in 
  Ahothrnim 
  rugosum 
  nuclei 
  

   are 
  present 
  in 
  the 
  latter 
  in 
  contrast 
  to 
  their 
  absence 
  in 
  the 
  former, 
  

   while 
  Erlanger 
  (1890) 
  in 
  Taenia 
  echinococcus 
  figures 
  them 
  in 
  both 
  

   of 
  these 
  membranes, 
  and 
  the 
  same 
  is 
  true 
  of 
  Bothriocephalns 
  laUis 
  

   according 
  to 
  Schmidt 
  (1888). 
  Salenskt 
  (1874) 
  in 
  Amphilina 
  and 
  

   MoNiEz 
  (1881) 
  in 
  several 
  species 
  deny 
  the 
  existence 
  of 
  a 
  definite 
  

   wall 
  in 
  the 
  vasa 
  efferentia, 
  these 
  representing 
  merely 
  channels 
  in 
  

   the 
  parenchyma. 
  

  

  This 
  divergence 
  of 
  opinion 
  is 
  probably 
  traceable 
  to 
  the 
  delicacy 
  

   of 
  the 
  structures 
  involved 
  and 
  the 
  difficulty 
  of 
  distinguishing 
  them 
  

   from 
  ordinary 
  parenchyma 
  strands, 
  with 
  which 
  they 
  are 
  in 
  direct 
  

   continuity 
  in 
  adult 
  as 
  well 
  as 
  embryonic 
  stages. 
  It 
  may 
  however 
  

   be 
  due 
  to 
  differences 
  in 
  structure 
  of 
  different 
  species. 
  

  

  The 
  second 
  stage 
  in 
  testis 
  development 
  is 
  marked 
  by 
  the 
  appear- 
  

  

  1) 
  See 
  YouNCx 
  (1908, 
  p. 
  191). 
  

  

  