﻿Eeproductive 
  organs 
  of 
  Taenia 
  pisiformis. 
  405 
  

  

  environment." 
  In 
  this 
  connection 
  he 
  cites 
  v. 
  Graff's 
  (1903) 
  

   observation 
  regarding' 
  the 
  loss 
  of 
  the 
  epithelium 
  in 
  Syncoelidium 
  a 
  

   parasitic 
  turbellarian, 
  and 
  its 
  replacement 
  "with 
  a 
  cuticula 
  similar 
  

   to 
  that 
  of 
  trematodes". 
  ^) 
  I 
  have 
  already 
  (Young, 
  1912b), 
  discussed 
  

   the 
  epithelial 
  relations 
  in 
  certain 
  Turbellaria 
  and 
  need 
  here 
  only 
  

   repeat 
  that 
  the 
  epithelium 
  of 
  Syncoelidium 
  is 
  not 
  ''similar 
  to 
  that 
  

   of 
  trematodes", 
  cell 
  boundaries 
  being 
  readily 
  demonstrable 
  in 
  the 
  

   former^), 
  and 
  further 
  that 
  similar 
  conditions 
  are 
  found 
  in 
  several 
  

   Turbellaria 
  which 
  are 
  not 
  parasitic 
  (viz. 
  PolycJwerus). 
  I 
  believe 
  

   however 
  as 
  previously 
  suggested 
  by 
  v. 
  Geaff 
  (1899), 
  myself 
  (1. 
  c), 
  

   and 
  others 
  that 
  epithelial 
  conditions 
  in 
  the 
  Turbellaria 
  are 
  prophetic 
  

   of 
  those 
  in 
  treraatodes 
  and 
  cestodes. 
  But 
  that 
  these 
  conditions 
  are 
  

   the 
  direct 
  result 
  of 
  the 
  parasitic 
  habit 
  of 
  the 
  latter 
  groups, 
  while 
  

   not 
  unlikely, 
  is 
  still 
  not 
  demonstrated. 
  

  

  Perhaps 
  the 
  most 
  interesting 
  question 
  in 
  cestode 
  development 
  

   is 
  that 
  of 
  the 
  manner 
  of 
  cell 
  increase. 
  It 
  is 
  only 
  of 
  late 
  years 
  that 
  

   this 
  question 
  has 
  received 
  much 
  attention, 
  but 
  recently 
  a 
  series 
  of 
  

   papers 
  by 
  Child, 
  Richards, 
  and 
  myself 
  have 
  treated 
  it 
  at 
  length. 
  

   Briefly 
  put 
  our 
  views 
  are 
  as 
  follows: 
  Child 
  maintains 
  that 
  amitosis 
  

   is 
  a 
  large 
  factor 
  in 
  cestode 
  development, 
  but 
  that 
  mitosis 
  also 
  plays 
  

   a 
  part, 
  the 
  relation 
  between 
  these 
  two 
  processes 
  being 
  uncertain. 
  

   Eichards 
  directly 
  opposes 
  Child 
  and 
  attempts 
  to 
  show 
  that 
  mitosis 
  

   is 
  sufficient 
  to 
  account 
  for 
  all 
  nuclear 
  increase 
  and 
  that 
  amitosis 
  is 
  

   not 
  evident. 
  I 
  have 
  endeavored 
  to 
  show 
  that 
  nucleoplasm 
  and 
  cyto- 
  

   plasm 
  are 
  fundamentally 
  the 
  same 
  and 
  that 
  the 
  latter 
  may 
  be 
  con- 
  

   verted 
  into 
  the 
  former 
  in 
  some 
  cases. 
  I 
  have 
  suggested 
  further 
  

   that 
  the 
  relative 
  scarcity 
  of 
  mitosis 
  and 
  the 
  occurrence 
  of 
  amitosis 
  

   and 
  de 
  novo 
  development 
  are 
  possibly 
  an 
  expression 
  of 
  the 
  degeneracy 
  

   of 
  this 
  group. 
  

  

  In 
  the 
  present 
  study 
  I 
  have 
  found 
  little 
  additional 
  evidence 
  of 
  

   -de 
  novo 
  development. 
  I 
  have 
  however 
  found 
  much 
  to 
  support 
  the 
  

   view 
  that 
  mitosis 
  in 
  cestodes 
  is 
  a 
  degenerating 
  process. 
  The 
  ap- 
  

   pearance 
  of 
  well 
  formed 
  skeins 
  in 
  both 
  testis 
  and 
  ovary 
  which 
  later 
  

   degenerate 
  *) 
  ; 
  the 
  absence 
  of 
  later 
  stages 
  of 
  mitosis 
  in 
  the 
  testis 
  of 
  

  

  1) 
  See 
  also 
  Ziegler 
  (1905) 
  in 
  this 
  connection. 
  

  

  2) 
  While 
  I 
  have 
  not 
  observed 
  this 
  in 
  Syncoelidium^ 
  I 
  have 
  in 
  the 
  

   closely 
  related 
  Bdelloiira. 
  

  

  4) 
  Fide 
  Child 
  (1907, 
  I 
  and 
  II) 
  in 
  both 
  ovary 
  and 
  testis 
  of 
  i/o/we;^/«, 
  

   Eichards 
  (1911) 
  in 
  ovary 
  of 
  Moiiiezia, 
  v. 
  Janicki 
  (1907) 
  in 
  ovary 
  of 
  

  

  Zool. 
  Jahrb 
  XXXV. 
  Abt. 
  f. 
  Anat. 
  27 
  

  

  