﻿402 
  ß- 
  T. 
  Young, 
  

  

  Early 
  Intermediate 
  Later 
  

  

  Number 
  of 
  embryos 
  232 
  217 
  87 
  

  

  Number 
  of 
  cells 
  974 
  1452 
  902 
  

  

  Number 
  of 
  mitoses 
  1? 
  18and21? 
  10and7? 
  

  

  The 
  occurence 
  of 
  early 
  cleavage 
  mitoses 
  as 
  described 
  by 
  Child 
  

   (1907, 
  in, 
  1911) 
  and 
  Richards 
  (1911) 
  in 
  Moniezia 
  and 
  v. 
  Janicki 
  

   (1907) 
  in 
  Taenia 
  serrata 
  I 
  have 
  not 
  seen 
  in 
  my 
  material. 
  

  

  Richards 
  (1911) 
  intimates 
  that 
  the 
  syncitial 
  character 
  of 
  the 
  

   embryos 
  described 
  by 
  Child 
  is 
  an 
  artifact 
  due 
  to 
  imperfect 
  fixation. 
  

   In 
  my 
  own 
  material 
  I 
  find 
  the 
  embryos 
  syncitial 
  in 
  character 
  at 
  

   all 
  stages, 
  and 
  the 
  same 
  is 
  true 
  in 
  AvitelUna 
  centripunctata 
  fide 
  

   GouGH 
  (1909 
  and 
  1911). 
  

  

  Discussion 
  of 
  results. 
  

  

  As 
  in 
  Cysticercus 
  so 
  in 
  Taenia 
  pisiformis 
  the 
  various 
  anlagen 
  

   arise 
  from 
  undifferentiated 
  parenchyma 
  cells. 
  That 
  some 
  of 
  these 
  

   anlagen 
  arise 
  from 
  independently 
  of 
  each 
  other 
  there 
  is 
  little 
  doubt, 
  

   but 
  regarding 
  them 
  all 
  a 
  final 
  statement 
  cannot 
  be 
  made. 
  The 
  evi- 
  

   dence 
  indicates 
  that 
  in 
  Taenia 
  pisiformis 
  at 
  least 
  there 
  are 
  several 
  

   growth 
  centers 
  in 
  the 
  reproductive 
  anlagen. 
  

  

  So 
  far 
  as 
  can 
  be 
  observed 
  there 
  is 
  no 
  difference 
  in 
  the 
  source 
  

   of 
  the 
  various 
  reproductive 
  organs, 
  all 
  arising 
  from 
  the 
  same 
  tissue 
  — 
  

   parenchyma. 
  Until 
  a 
  comparatively 
  late 
  period 
  in 
  the 
  development 
  

   of 
  the 
  organism 
  they 
  are 
  not 
  differentiated. 
  The 
  cause 
  of 
  their 
  

   differentiation 
  is 
  as 
  yet 
  entirely 
  unknown. 
  The 
  existence 
  of 
  cell 
  

   determinants 
  of 
  any 
  kind 
  wiiatsoever, 
  which 
  are 
  carried 
  thru 
  the 
  

   non-sexual 
  larva 
  and 
  young 
  proglottid 
  s 
  to 
  the 
  older 
  proglottids, 
  there 
  

   to 
  give 
  rise 
  to 
  sex 
  organs 
  seems 
  highly 
  improbable. 
  It 
  seems 
  far 
  

   more 
  likely 
  that 
  every 
  cell 
  possesses 
  the 
  power 
  to 
  form 
  part 
  of 
  any 
  

   organ 
  provided 
  it 
  be 
  rightly 
  situated. 
  While 
  heredity 
  is 
  undoubt- 
  

   edly 
  the 
  main 
  factor 
  in 
  development, 
  determining 
  the 
  form 
  and 
  

   approximate 
  time 
  of 
  appearance 
  of 
  parts, 
  cell 
  environment 
  is 
  probably 
  

   a 
  secondary 
  factor 
  of 
  great 
  importance 
  in 
  determining 
  the 
  fate 
  of 
  

   individual 
  cells. 
  In 
  this 
  connection 
  the 
  observations 
  of 
  Child 
  (1906 
  

   and 
  1907, 
  II) 
  that 
  differentiated 
  muscle 
  cells 
  may 
  occasionally 
  give 
  

   rise 
  to 
  testes 
  is 
  of 
  great 
  interest. 
  In 
  the 
  w^ords 
  of 
  this 
  author, 
  

  

  is 
  much 
  greater 
  than 
  this. 
  Many 
  of 
  the 
  cases 
  recorded 
  are 
  marked? 
  

   because 
  very 
  uncertain. 
  

  

  