﻿452 
  J. 
  W. 
  JENKTNSON. 
  

  

  wliich 
  he 
  understands 
  the 
  reticular 
  spherical 
  body 
  from 
  which 
  

   the 
  rays 
  of 
  the 
  aster 
  start, 
  j^rows 
  in 
  the 
  anaphase 
  and 
  gradu- 
  

   ally 
  merges 
  with 
  the 
  aster. 
  Meanwhile, 
  by 
  condensation 
  of 
  

   the 
  central 
  portion 
  of 
  the 
  old, 
  a 
  new 
  centrosome 
  is 
  formed, 
  

   which 
  divides, 
  and 
  is 
  the 
  starting-point 
  for 
  new 
  asters 
  and 
  a 
  

   new 
  spindle. 
  

  

  In 
  Ascaris 
  the 
  process 
  is 
  a 
  little 
  different. 
  Here 
  the 
  

   centrosome 
  enlarges 
  until 
  the 
  metaphase 
  is 
  reached 
  ; 
  it 
  then 
  

   begins 
  to 
  diminish, 
  and 
  continues 
  to 
  do 
  so 
  until 
  it 
  divides. 
  It 
  

   should 
  be 
  noticed 
  that 
  a 
  centriole 
  is 
  distinctly 
  visible 
  in 
  its 
  

   interior 
  throughout. 
  What 
  happens 
  during 
  its 
  diminution 
  

   may 
  best 
  be 
  described 
  in 
  Boveri^s 
  own 
  words 
  : 
  " 
  Natiirlich 
  

   mussen 
  gewisse 
  Teile 
  abgestossen 
  werden 
  ; 
  allein 
  dieser 
  Pro- 
  

   zess 
  scheint 
  sich 
  in 
  den 
  meisten 
  Fallen 
  so 
  allmahlich 
  zu 
  

   vollziehen 
  dass 
  er 
  kaum 
  bemerkbar 
  ist 
  und 
  die 
  abgestossene 
  

   Teile 
  nicht 
  als 
  solche 
  erkannt 
  werden 
  konnen 
  " 
  (the 
  surface 
  

   of 
  the 
  centrosome 
  is 
  rough 
  and 
  ragged 
  at 
  this 
  stage) 
  ; 
  " 
  diese 
  

   Bilder 
  mogen 
  mit 
  der 
  Auflosung 
  peripherer 
  Centroplasmasch- 
  

   ichten 
  zusammenhangen." 
  Again 
  he 
  says 
  : 
  " 
  Das 
  verkleinerte 
  

   Centrosom 
  ist 
  stets 
  der 
  Mittelpunkt 
  der 
  Radien 
  die 
  sich 
  ihm 
  

   unmittelbar 
  anfiigen 
  und 
  die 
  olfenbar 
  aus 
  dem 
  abgestossenen 
  

   Centroplasma 
  gebildet 
  sind.'^ 
  Finally 
  he 
  concludes 
  : 
  " 
  Das 
  

   periphere 
  Centroplasma 
  sich 
  von 
  dem 
  centralen 
  gesondert 
  und 
  

   ahnlich 
  wie 
  beim 
  Seeigelei 
  der 
  Sphare 
  angeschlossen 
  hat." 
  

  

  I 
  think 
  it 
  is 
  perfectly 
  clear 
  from 
  this 
  that 
  Boveri 
  regards 
  

   the 
  diminution 
  of 
  the 
  centrosome 
  in 
  the 
  anaphase 
  of 
  Ascaris 
  

   as 
  parallel 
  to 
  the 
  condensation 
  of 
  a 
  new 
  centrosome 
  in 
  the 
  

   interior 
  of 
  the 
  old 
  in 
  Echinus. 
  In 
  that 
  case 
  the 
  only 
  differ- 
  

   ence 
  between 
  the 
  two 
  is 
  this 
  : 
  in 
  Echinus 
  the 
  centrosome 
  

   grows 
  by 
  simple 
  enlargement, 
  in 
  Ascaris 
  it 
  grows 
  by 
  giving 
  

   off 
  rays 
  which 
  become 
  continuous 
  with 
  the 
  older 
  rays 
  outside. 
  

   In 
  both 
  cases 
  the 
  outer 
  portion 
  of 
  the 
  enlarged 
  centrosome 
  

   becomes 
  indistinguishable 
  from 
  the 
  aster, 
  and 
  together 
  with 
  it 
  

   undergoes 
  a 
  granular 
  or 
  reticular 
  degeneration. 
  

  

  The 
  changes 
  figured 
  by 
  Conklin 
  in 
  Crepidula 
  are 
  closely 
  

   similar 
  to 
  those 
  described 
  by 
  Boveri 
  for 
  Echinus 
  ; 
  the 
  same 
  

   may 
  be 
  said 
  of 
  Sobotta's 
  figures 
  of 
  Amphioxus, 
  Coe's 
  of 
  

  

  