﻿Eeproductive 
  organs 
  of 
  Taenia 
  pisiformis. 
  399 
  

  

  occurring 
  in 
  the 
  oviduct, 
  and 
  the 
  observations 
  of 
  Child 
  (1907, 
  III) 
  

   and 
  EiCHARDS 
  (1911) 
  on 
  MonieHa 
  confirm 
  this, 
  while 
  my 
  own 
  obser- 
  

   vations 
  indicate 
  that 
  it 
  may 
  occur 
  in 
  the 
  uterus.^) 
  

  

  In 
  proglottids 
  whose 
  seminal 
  receptacles 
  are 
  distended 
  with 
  

   sperm 
  one 
  finds 
  in 
  the 
  uterus 
  large 
  numbers 
  of 
  spermatozoa 
  mingled 
  

   with 
  the 
  eggs 
  and 
  embryos. 
  These 
  sperms 
  are 
  much 
  coiled 
  and. 
  

   twisted, 
  being 
  frequently 
  coiled 
  about 
  the 
  eggs 
  (Figs. 
  31 
  and 
  83).^) 
  In 
  

   such 
  animals 
  as 
  cestodes 
  where 
  it 
  is 
  impossible 
  to 
  study 
  the 
  entrance 
  

   of 
  the 
  sperm 
  into 
  the 
  ^^g, 
  it 
  is 
  obviously 
  more 
  diificult 
  than 
  in 
  

   living 
  material 
  to 
  follow 
  the 
  exact 
  course 
  of 
  events. 
  I 
  have 
  been 
  

   unable 
  to 
  identify 
  any 
  sperm 
  just 
  at 
  the 
  moment 
  of 
  entering 
  the 
  

   ^^g, 
  but 
  have 
  observed 
  uterine 
  eggs 
  which 
  apparently 
  had 
  been 
  

   but 
  recently 
  fertilized 
  (Figs. 
  31, 
  83 
  and 
  84). 
  Apparently 
  sperm 
  en- 
  

   trance 
  does 
  not 
  incite 
  any 
  appreciable 
  change 
  in 
  the 
  ^gg, 
  fertilized 
  

   eggs 
  appearing 
  similar 
  to 
  unfertilized 
  ones. 
  I 
  have 
  not 
  observed 
  

   the 
  formation 
  of 
  a 
  fertilization 
  membrane 
  such 
  as 
  Moniez 
  (1881) 
  has 
  

   described 
  in 
  T. 
  expansa, 
  cucumerina 
  etc. 
  and 
  Richards 
  (1911) 
  in 
  

   Moniesia. 
  There 
  is 
  no 
  evidence 
  to 
  indicate 
  the 
  cause 
  of 
  sperm 
  

   entrance, 
  whether 
  this 
  is 
  due 
  merely 
  to 
  chemical 
  affinity 
  between 
  

   ^gg 
  and 
  sperm 
  or 
  to 
  active 
  movement 
  of 
  the 
  latter. 
  Child 
  (1907, 
  II) 
  

   however 
  has 
  observed 
  no 
  movement 
  in 
  fresh 
  spermatozoa 
  of 
  

   Moniezia, 
  hence 
  in 
  this 
  genus 
  at 
  least 
  the 
  latter 
  hypothesis 
  is 
  

   unlikely. 
  

  

  The 
  sperm 
  appears 
  to 
  undergo 
  no 
  immediate 
  change 
  upoa 
  

   entering 
  the 
  ^gg. 
  A 
  small 
  part 
  of 
  it 
  only 
  is 
  found 
  within 
  the 
  latter, 
  

   its 
  diameter 
  remaining 
  the 
  same 
  as 
  before 
  entrance. 
  Soon 
  however 
  

   part 
  of 
  the 
  end 
  within 
  the 
  ^gg 
  increases 
  to 
  form 
  a 
  small 
  ovoid 
  body 
  

   (Figs. 
  83 
  and 
  84), 
  the 
  remainder 
  being 
  apparently 
  absorbed 
  by 
  the 
  

   ^gg. 
  The 
  part 
  outside 
  the 
  ^gg 
  remains 
  for 
  a 
  time 
  unchanged 
  but 
  

   ultimately 
  disappears. 
  The 
  source 
  of 
  increase 
  of 
  the 
  anterior 
  end, 
  or 
  as 
  

   it 
  may 
  now 
  be 
  termed 
  male 
  pronucleus, 
  is 
  uncertain. 
  It 
  increases 
  

   coincidently 
  with 
  the 
  disappearance 
  of 
  the 
  rest 
  of 
  the 
  intra-ovum 
  sperm, 
  

   but 
  whether 
  by 
  absorption 
  of 
  the 
  latter 
  or 
  of 
  material 
  from 
  the 
  

   surrounding 
  cytoplasm 
  cannot 
  be 
  said. 
  The 
  further 
  history 
  of 
  the 
  

   male 
  pronucleus 
  is 
  somewhat 
  uncertain. 
  This 
  is 
  because 
  of 
  the 
  ease 
  

  

  1) 
  I 
  base 
  this 
  statement 
  chiefly 
  on 
  the 
  presence 
  of 
  both 
  sperms 
  and 
  

   apparently 
  unfertilized 
  eggs 
  in 
  this 
  organ. 
  

  

  2) 
  The 
  same 
  phenomenon 
  has 
  been 
  noted 
  by 
  Child 
  (1907 
  III) 
  in 
  

  

  Moniexia. 
  

  

  