﻿356 
  R- 
  T. 
  Young, 
  

  

  How 
  far 
  is 
  the 
  fate 
  of 
  any 
  cell 
  inherent 
  in 
  the 
  cell 
  itself 
  and 
  

   how 
  far 
  dependent 
  on 
  the 
  cell's 
  environment? 
  

  

  Are 
  polar 
  bodies 
  formed 
  and 
  how? 
  

  

  Has 
  the 
  cestode 
  nucleus 
  a 
  morphological 
  or 
  a 
  physiological 
  

   significance 
  or 
  both, 
  and 
  what 
  is 
  its 
  origin? 
  

  

  These 
  are 
  the 
  principal 
  questions 
  with 
  which 
  the 
  following 
  

   paper 
  will 
  attempt 
  to 
  deal. 
  

  

  The 
  fixative 
  used 
  in 
  this 
  study 
  was 
  chiefly 
  Flemming's 
  chrom- 
  

   aceto-osmic 
  mixture 
  (strong 
  solution), 
  tho 
  mercuric 
  solutions 
  were 
  

   used 
  for 
  some 
  of 
  the 
  tissue. 
  The 
  former 
  gave 
  in 
  general 
  the 
  best 
  

   results. 
  Sections 
  5 
  ijl 
  thick 
  were 
  cut 
  in 
  paraffin 
  and 
  stained 
  in 
  

   Heidenhain's 
  iron 
  haematoxylin 
  and 
  lightly 
  counterstained 
  in 
  most 
  

   cases 
  with 
  eosin. 
  Preparations 
  of 
  isolated 
  eggs 
  were 
  also 
  made 
  and 
  

   stained 
  in 
  Delaeield's 
  haematoxylin 
  and 
  eosin. 
  The 
  photomicrographs 
  

   were 
  taken 
  on 
  Cramee's 
  isochromatic 
  plates, 
  the 
  arc 
  light 
  ^) 
  being 
  

   the 
  illuminant 
  used, 
  and 
  a 
  ra}' 
  filter 
  of 
  potassium 
  bichromate 
  

   employed. 
  

  

  The 
  earliest 
  anläge 
  of 
  the 
  reproductive 
  organs 
  in 
  Taenia 
  pisiformis 
  

   appears 
  in 
  about 
  the 
  twentj^-fifth 
  or 
  thirtieth 
  proglottid 
  as 
  a 
  slender 
  

   cord 
  of 
  closely 
  grouped 
  nuclei 
  embedded 
  in 
  a 
  mass 
  of 
  delicate 
  fibrillae 
  

   near 
  the 
  center 
  of 
  the 
  proglottid 
  (Fig. 
  1). 
  From 
  its 
  point 
  of 
  origin 
  

   the 
  anläge 
  grows 
  peripherally 
  soon 
  dividing 
  into 
  two 
  parts, 
  the 
  

   anterior 
  being 
  the 
  anläge 
  of 
  the 
  vas 
  deferens, 
  and 
  the 
  posterior 
  

   that 
  of 
  the 
  vagina. 
  The 
  division 
  occurs 
  first 
  medially 
  extending 
  

   peripherally 
  later. 
  As 
  the 
  common 
  anläge 
  grows 
  toward 
  the 
  edge 
  

   of 
  the 
  proglottid 
  there 
  is 
  no 
  ingrowth 
  of 
  cells 
  to 
  meet 
  it. 
  It 
  in- 
  

   creases 
  thru 
  multiplication 
  of 
  its 
  own 
  cells, 
  those 
  of 
  the 
  parenchyma 
  

   in 
  its 
  path 
  being 
  gradually 
  added 
  to 
  it, 
  until 
  it 
  final!}' 
  reaches 
  the 
  

   periphery. 
  

  

  Medially 
  the 
  anläge 
  of 
  the 
  vas 
  deferens 
  passes 
  in 
  to 
  the 
  

   middle 
  of 
  the 
  proglottid 
  and 
  there 
  disappears. 
  That 
  of 
  the 
  vagina 
  

   as 
  it 
  lengthens 
  becomes 
  very 
  thin 
  in 
  part 
  of 
  its 
  extent, 
  and 
  passes 
  

   posteriorly 
  as 
  well 
  as 
  medially. 
  In 
  the 
  posterior 
  part 
  of 
  the 
  pro- 
  

   glottid 
  it 
  terminates 
  in 
  an 
  enlargement 
  — 
  the 
  anläge 
  of 
  the 
  shell 
  

   gland 
  plus 
  part 
  of 
  the 
  oviduct 
  2) 
  and 
  uterus 
  (Fig. 
  2). 
  

  

  The 
  uterus 
  has 
  appeared 
  meanwhile 
  as 
  a 
  slender 
  cord 
  of 
  cells 
  

  

  1) 
  Toward 
  the 
  end 
  of 
  the 
  work 
  Nernst 
  glowers 
  were 
  substituted 
  

   for 
  the 
  arc 
  Hght 
  and 
  proved 
  much 
  more 
  satisfactory. 
  

  

  2) 
  See 
  Footnote 
  3 
  page 
  366 
  for 
  my 
  definition 
  of 
  this 
  term. 
  

  

  