﻿380 
  ß. 
  T. 
  Young, 
  

  

  sented 
  in 
  Fig. 
  49, 
  in 
  which 
  the 
  elongating* 
  spermatocyte 
  shows 
  two 
  

   definite 
  peripheral 
  lines 
  at 
  x, 
  which 
  unite 
  after 
  a 
  short 
  course 
  ta 
  

   form 
  a 
  single 
  filament. 
  If 
  we 
  imagine 
  a 
  considerable 
  elongation 
  

   and 
  consequent 
  constriction 
  of 
  such 
  a 
  structure 
  we 
  can 
  readilj^ 
  

   derive 
  from 
  it 
  a 
  hollow 
  sperm, 
  such 
  as 
  is 
  shown 
  in 
  Fig. 
  54. 
  Varying 
  

   stages 
  in 
  the 
  elongation 
  of 
  similar 
  structures 
  are 
  in 
  fact 
  shown 
  

   occasionally 
  in 
  the 
  cytophores. 
  The 
  tubular 
  sperms 
  become 
  solid 
  by 
  

   condensation 
  progressing 
  either 
  from 
  one 
  point 
  on 
  the 
  periphery 
  or 
  

   from 
  all 
  points 
  simultaneously. 
  In 
  the 
  former 
  case 
  there 
  is 
  a 
  dense 
  

   line 
  running 
  along 
  one 
  part 
  of 
  the 
  sperm. 
  Transitional 
  stages 
  

   between 
  hollow 
  and 
  solid 
  sperms 
  are 
  found 
  mingled 
  with 
  the 
  others, 
  

   Fig. 
  54. 
  

  

  A 
  difterentiation 
  of 
  the 
  spermatozoa 
  of 
  Taenia 
  pisiformis 
  into 
  

   head, 
  middle 
  piece, 
  tail 
  or 
  other 
  parts 
  is 
  impossible, 
  at 
  least 
  with 
  

   the 
  methods 
  of 
  technique 
  which 
  I 
  have 
  employed. 
  How 
  much 
  of 
  

   the 
  sperm 
  is 
  chromatin 
  therefore 
  I 
  cannot 
  say. 
  In 
  fertilization, 
  as 
  

   will 
  be 
  seen 
  later, 
  a 
  comparatively 
  small 
  part 
  of 
  the 
  sperm 
  gives 
  

   rise 
  to 
  the 
  male 
  pronucleus, 
  but 
  in 
  development 
  there 
  is 
  no 
  evident 
  

   concentration 
  of 
  chromatin 
  in 
  any 
  part. 
  Whether 
  there 
  is 
  a 
  speci- 
  

   alized 
  part 
  of 
  the 
  sperm 
  which 
  forms 
  the 
  pronucleus, 
  or 
  whether 
  

   the 
  former 
  is 
  homogeneous 
  thruout, 
  the 
  formation 
  of 
  the 
  latter 
  being 
  

   a 
  quantitative 
  rather 
  than 
  qualitative 
  process, 
  is 
  uncertain. 
  So 
  far 
  

   as 
  m}^ 
  evidence 
  goes 
  the 
  latter 
  is 
  the 
  more 
  probable 
  hypothesis.. 
  

   The 
  source 
  of 
  the 
  spermatic 
  chromatin 
  is 
  probably 
  the 
  primary 
  

   spermatocytic 
  skeins 
  which, 
  as 
  stated 
  above, 
  become 
  scattered 
  thru- 
  

   out 
  the 
  cytophore; 
  and 
  the 
  absence 
  of 
  any 
  evident 
  participation 
  of 
  

   chromatin 
  in 
  the 
  formation 
  of 
  the 
  spermatozoan 
  in 
  many 
  cases, 
  may 
  

   mean 
  simply 
  that 
  the 
  chromatin 
  enters 
  the 
  latter 
  in 
  a 
  diifuse 
  con-^ 
  

   dition. 
  

  

  The 
  absence 
  of 
  a 
  distinct 
  head 
  in 
  the 
  spermatozoa 
  of 
  several 
  

   cestodes 
  has 
  been 
  mentioned 
  by 
  various 
  authors. 
  Thus 
  Saleksky 
  

   (1874, 
  p. 
  318) 
  describes 
  those 
  of 
  Amphilina 
  as 
  ". 
  . 
  . 
  sehr 
  lang 
  . 
  . 
  . 
  

   an 
  einem 
  P^nde 
  etwas 
  gekrümmt. 
  Diese 
  Krümmung 
  soll 
  aber 
  nicht 
  

   als 
  Köpfchen 
  angesehen 
  werden, 
  in 
  dem 
  die 
  Spermatozoen 
  in 
  ihrer 
  

   ganzen 
  Länge 
  gleich 
  dick 
  sind"'. 
  Moniez 
  (1878, 
  p. 
  113), 
  speaking 
  

   of 
  the 
  sperms 
  of 
  several 
  cestodes, 
  says, 
  ". 
  . 
  . 
  que 
  leur 
  tête 
  s'atrophie 
  

   comme 
  l'on 
  sait", 
  and 
  Leuckart 
  (1886, 
  p. 
  438) 
  speaks 
  of 
  the 
  sperms 
  

   of 
  Taenia 
  saginata 
  as 
  possessing 
  a 
  "hardly 
  defined" 
  head. 
  Child 
  

   (1907, 
  II) 
  describes 
  the 
  spermatozoa 
  of 
  Moniesia 
  as 
  showing 
  no 
  evident 
  

   head 
  either 
  in 
  the 
  fresh 
  condition 
  or 
  in 
  stained 
  preparations. 
  Accord- 
  

  

  