﻿384 
  ^' 
  T. 
  Young, 
  

  

  The 
  second 
  type 
  of 
  nucleus 
  described 
  by 
  Child 
  is 
  destined 
  to- 
  

   give 
  rise 
  to 
  spermatid 
  nuclei 
  by 
  fragmentation. 
  In 
  this 
  process 
  the 
  

   nuclear 
  membrane 
  and 
  skeins 
  degenerate 
  and 
  neAv 
  nuclei 
  appear 
  in 
  

   the 
  cavity 
  of 
  the 
  old 
  nucleus. 
  No 
  positive 
  evidence 
  that 
  the 
  new 
  

   nuclei 
  arise 
  by 
  fragmentation 
  of 
  the 
  old 
  is 
  here 
  given, 
  the 
  process 
  

   appearing 
  essentially 
  similar 
  to 
  that 
  described 
  above 
  by 
  me 
  ^), 
  in 
  

   which 
  the 
  primary 
  spermatocyte 
  nuclei 
  break 
  up 
  and 
  are 
  replaced 
  

   by 
  the 
  secondary 
  which 
  are 
  probably 
  formed 
  from 
  their 
  remnants. 
  

  

  My 
  account 
  of 
  spermatogenesis 
  differs 
  further 
  from 
  that 
  of 
  

   Child 
  in 
  that 
  I, 
  in 
  most 
  cases, 
  derive 
  the 
  sperm 
  from 
  the 
  cytoplasm 
  

   of 
  the 
  cytophore, 
  while 
  he 
  derives 
  them 
  from 
  a 
  spermatid 
  nucleus. 
  

   In 
  only 
  a 
  few 
  cases 
  have 
  I 
  observed 
  direct 
  continuity 
  between 
  

   nuclei 
  ^) 
  and 
  sperm 
  (Figs. 
  44—46, 
  and 
  49), 
  such 
  as 
  he 
  describes 
  as 
  

   typical 
  in 
  Moniezia, 
  and 
  where 
  such 
  a 
  connection 
  does 
  exist 
  I 
  dO' 
  

   not 
  consider 
  it 
  important 
  as 
  I 
  have 
  already 
  explained.^) 
  

  

  GouGH 
  (1909) 
  has 
  given 
  an 
  account 
  of 
  spermatogenesis 
  in 
  

   Stilesia 
  centripunctata 
  which 
  in 
  some 
  respects 
  resembles 
  mine. 
  Ac- 
  

   cording 
  to 
  him 
  in 
  an 
  early 
  stage 
  the 
  testis 
  is 
  a 
  syncytium 
  of 
  four 
  

   nuclei. 
  Cellular 
  increase 
  takes 
  place 
  at 
  first 
  by 
  amitosis. 
  After 
  the 
  

   first 
  spermatocytic 
  division 
  a 
  cytophore 
  is 
  formed, 
  and 
  the 
  ^'nuclei 
  

   resolve 
  themselves 
  into 
  chromatin 
  threads 
  and 
  wander 
  into 
  the 
  in- 
  

   terior 
  of 
  the 
  syncitium, 
  all 
  traces 
  of 
  the 
  single 
  component 
  cells 
  be- 
  

   coming 
  lost. 
  . 
  . 
  . 
  The 
  chromatin 
  then 
  seems 
  to 
  break 
  up 
  into 
  short 
  

   lengths, 
  each 
  of 
  which 
  . 
  . 
  . 
  forms 
  the 
  nucleus 
  of 
  a 
  new 
  cell. 
  These 
  

   cells 
  after 
  further 
  division 
  give 
  rise 
  to 
  spermatozoa" 
  (1. 
  c, 
  p. 
  128 
  

   —129). 
  

  

  The 
  ovary 
  and 
  oogenesis. 
  The 
  anläge 
  of 
  the 
  ovary 
  has 
  

   already 
  been 
  briefly 
  described. 
  Two 
  parts 
  must 
  be 
  distinguished 
  

   — 
  the 
  anlagen 
  of 
  the 
  ducts 
  and 
  those 
  of 
  the 
  follicles. 
  The 
  

   development 
  of 
  the 
  former 
  having 
  been 
  already 
  discussed, 
  that 
  of 
  

   the 
  latter 
  alone 
  concerns 
  us 
  here. 
  These 
  arise 
  in 
  situ 
  in 
  

   the 
  parenchyma 
  becoming 
  united 
  at 
  an 
  early 
  stage 
  with 
  the 
  former. 
  

   The 
  early 
  development 
  of 
  the 
  follicles 
  is 
  similar 
  to 
  that 
  of 
  the 
  

   testes 
  described 
  above, 
  the 
  early 
  oogonia^) 
  being 
  identical 
  both 
  in 
  

  

  1) 
  Except 
  for 
  the 
  persistence 
  of 
  a 
  "nucleolus" 
  in 
  Moniezia. 
  This 
  I 
  

   have 
  not 
  observed 
  in 
  Taenia 
  pisiformis. 
  

  

  2) 
  Secondary 
  spermatocytes 
  according 
  to 
  my 
  terminology, 
  spermatid* 
  

   according 
  to 
  that 
  of 
  Child. 
  

  

  3) 
  See 
  page 
  379. 
  

  

  4) 
  At 
  Dahlgren's 
  suggestion 
  Eichards 
  (1911) 
  applies 
  the 
  term 
  

  

  