﻿Reproductive 
  organs 
  of 
  Taenia 
  pisiformis. 
  383 
  

  

  p. 
  181). 
  The 
  former 
  type 
  is 
  preparing 
  for 
  the 
  first 
  maturation 
  mitosis^ 
  

   while 
  the 
  latter 
  is 
  destined 
  to 
  give 
  rise 
  to 
  spermatozoa 
  by 
  amitosis. 
  

   The 
  number 
  of 
  chromosomes 
  in 
  the 
  first 
  maturation 
  division 
  is 
  un- 
  

   €ertain, 
  apparently 
  varying 
  in 
  the 
  two 
  species 
  (expansa 
  and 
  planis- 
  

   sima), 
  and 
  even 
  in 
  the 
  same 
  species 
  within 
  somewhat 
  wide 
  limits, 
  

   from 
  six 
  to 
  eight 
  in 
  the 
  former 
  and 
  from 
  five 
  to 
  thirteen 
  in 
  

   the 
  latter. 
  Child's 
  statements 
  are 
  not 
  positive 
  regarding 
  the 
  

   chromosome 
  number 
  however 
  and 
  where 
  the 
  number 
  is 
  smaller 
  it 
  is 
  

   possible 
  that 
  some 
  or 
  all 
  of 
  the 
  chromosomes 
  are 
  double. 
  In 
  Taenia 
  

   pisiformis 
  I 
  have 
  found 
  practically 
  no 
  mitotic 
  stages 
  ^) 
  later 
  than 
  the 
  

   prophase 
  in 
  spermatogenesis, 
  and 
  hence 
  have 
  had 
  no 
  opportunity 
  of 
  

   making 
  chromosome 
  counts. 
  In 
  oogenesis 
  however 
  numerous 
  abortive 
  

   maturation 
  divisions 
  occur, 
  and 
  I 
  have 
  some 
  evidence 
  of 
  variation 
  

   in 
  chromosome 
  number.^) 
  

  

  According 
  to 
  Child 
  tetrads 
  are 
  not 
  formed 
  in 
  Moniema, 
  the 
  

   chromosomes 
  in 
  the 
  first 
  maturation 
  division 
  having 
  the 
  form 
  of 
  dy- 
  

   ads. 
  He 
  could 
  not 
  determine 
  the 
  direction 
  of 
  division 
  of 
  these 
  dyads, 
  

   and 
  while 
  he 
  says 
  that 
  ". 
  . 
  . 
  they 
  correspond 
  as 
  regards 
  ultimate 
  

   fate 
  with 
  the 
  tetrads 
  of 
  various 
  authors" 
  (1, 
  c, 
  p. 
  192), 
  neither 
  his 
  

   account 
  nor 
  his 
  figures 
  make 
  plain 
  what 
  this 
  ultimate 
  fate 
  is. 
  The 
  

   first 
  division 
  is 
  followed 
  by 
  the 
  second 
  without 
  any 
  intervening 
  rest- 
  

   ing 
  stage, 
  at 
  least 
  in 
  most 
  cases. 
  The 
  chromosome 
  number 
  not 
  being 
  

   certain 
  in 
  either 
  division, 
  and 
  none 
  of 
  the 
  cytophores 
  described 
  or 
  

   figured 
  showing 
  any 
  evidence 
  of 
  two 
  successive 
  divisions, 
  it 
  is 
  not 
  

   €lear 
  by 
  what 
  evidence 
  Child 
  determines 
  the 
  occurrence 
  of 
  two 
  

   divisions, 
  or 
  which 
  division 
  any 
  given 
  cytophore 
  represents. 
  Com- 
  

   pare 
  his 
  figs. 
  18 
  — 
  20 
  with 
  25 
  and 
  26, 
  for 
  example. 
  What 
  is 
  there 
  

   in 
  structure 
  or 
  arrangement 
  of 
  these 
  figures 
  to 
  show 
  to 
  which 
  

   division 
  any 
  one 
  belongs? 
  What 
  evidence 
  is 
  there 
  in 
  fact 
  to 
  

   show 
  that 
  two 
  divisions 
  exist? 
  There 
  is 
  some 
  difference 
  indeed 
  in 
  

   the 
  size 
  of 
  the 
  spindles 
  of 
  the 
  first 
  and 
  second 
  divisions. 
  But 
  

   this 
  is 
  apparently 
  the 
  only 
  difference, 
  and 
  it 
  can 
  hardly 
  be 
  said 
  to 
  

   be 
  conclusive. 
  He 
  gives 
  no 
  evidence 
  of 
  reduction 
  of 
  chromosomes, 
  

   while 
  synapsis, 
  which 
  typically 
  precedes 
  the 
  spermatocyte 
  divisions, 
  

   is 
  not 
  mentioned.^) 
  

  

  1) 
  See 
  page 
  377, 
  

  

  2) 
  See 
  page 
  391, 
  392. 
  

  

  3) 
  Unless 
  his 
  statements 
  on 
  p. 
  191 
  "... 
  some 
  of 
  these 
  masses 
  

   appear 
  to 
  be 
  grouped 
  in 
  pairs", 
  and 
  p. 
  192, 
  "... 
  the 
  fusion 
  of 
  the 
  

   two 
  parts 
  . 
  . 
  ." 
  refer 
  to 
  this 
  process. 
  

  

  