﻿422 
  J. 
  W. 
  JENKINSON. 
  

  

  tlie 
  egg. 
  In 
  immediate 
  proximity 
  to 
  the 
  sperm-head 
  are 
  a 
  

   few 
  clear 
  vacuoles. 
  

  

  The 
  structure 
  of 
  the 
  axolotl-spermatozoon 
  is 
  well 
  known, 
  

   and 
  closely 
  resembles 
  that 
  of 
  the 
  salamander 
  and 
  newt. 
  

   The 
  head 
  is 
  very 
  long, 
  and 
  tapers 
  to 
  the 
  apex, 
  the 
  tail 
  is 
  even 
  

   longer, 
  and 
  provided 
  with 
  an 
  undulating 
  membrane 
  or 
  fin. 
  

   The 
  middle-piece 
  is 
  embedded 
  in 
  the 
  posterior 
  end 
  of 
  the 
  

   head, 
  and 
  stains 
  less 
  deeply 
  than 
  the 
  latter 
  with 
  iron-hseraa- 
  

   toxylin, 
  while 
  with 
  gentian-violet 
  and 
  orange, 
  and 
  borax- 
  

   carmine 
  and 
  picro-indigo 
  -carmine 
  it 
  takes 
  in 
  each 
  case 
  the 
  

   plasma 
  staiu. 
  This 
  middle-piece 
  is 
  derived 
  in 
  the 
  axolotl 
  — 
  

   as 
  Meves 
  (1897) 
  has 
  shown 
  it 
  to 
  be 
  in 
  the 
  salamander 
  — 
  from 
  

   one 
  of 
  the 
  two 
  centrosomes 
  of 
  the 
  spermatid. 
  

  

  The 
  sperm 
  may 
  enter 
  at 
  any 
  point 
  in 
  the 
  animal 
  hemi- 
  

   sphere, 
  and 
  sometimes 
  even 
  a 
  little 
  way 
  below 
  the 
  equator. 
  

  

  In 
  the 
  Axolotl 
  polyspermy 
  is 
  normally 
  of 
  frequent 
  occur- 
  

   rence, 
  and 
  two 
  sperms 
  may 
  even 
  enter 
  by 
  the 
  same 
  funnel. 
  

   There 
  is 
  nothing 
  to 
  distinguish 
  the 
  accessory 
  spermatozoa 
  

   from 
  that 
  one 
  which 
  copulates 
  with 
  the 
  female 
  pronucleus. 
  

   The 
  changes 
  they 
  all 
  go 
  through 
  are 
  similar 
  and 
  practically 
  

   synchronous, 
  and 
  centrosomes 
  are 
  formed 
  — 
  as 
  we 
  shall 
  see 
  

   later 
  on 
  — 
  in 
  connection 
  with 
  them 
  all. 
  There 
  is 
  no 
  fact 
  that 
  

   I 
  am 
  aware 
  of 
  to 
  indicate 
  that 
  this 
  process 
  is 
  pathological 
  ; 
  it 
  

   must, 
  on 
  the 
  contrary, 
  be 
  compared 
  with 
  the 
  exactly 
  similar 
  

   physiological 
  polyspermy 
  observed 
  by 
  Riickert 
  (1899) 
  in 
  

   Elasmobranchs 
  and 
  by 
  Oppel 
  and 
  Nicolas 
  in 
  Reptilia. 
  Of 
  

   the 
  ultimate 
  fate 
  of 
  these 
  accessory 
  spermatozoa 
  I 
  am 
  not 
  in 
  

   a 
  position 
  to 
  say 
  anything. 
  

  

  3. 
  Changes 
  in 
  the 
  spermatozoon; 
  development 
  

   of 
  the 
  sperm 
  aster; 
  disappearance 
  of 
  the 
  

   mid 
  die- 
  piece. 
  

  

  The 
  sperm-head 
  soon 
  begins 
  to 
  shorten 
  and 
  thicken 
  ; 
  at 
  the 
  

   same 
  time 
  a 
  few 
  small 
  vacuoles 
  make 
  their 
  appearance 
  in 
  its 
  

   substance, 
  which 
  thus 
  comes 
  to 
  have 
  an 
  extremely 
  coarse 
  reti- 
  

   cular 
  appearance 
  (fig. 
  16). 
  This 
  is 
  the 
  first 
  indication 
  of 
  the 
  

  

  