﻿450 
  J. 
  W. 
  JliNKlNSON. 
  

  

  In 
  the 
  primary 
  spermatocytes 
  of 
  Ascaris, 
  Brauer 
  (1893) 
  has 
  

   observed 
  and 
  figvired 
  the 
  appearance 
  and 
  even 
  the 
  division 
  of 
  

   the 
  centrosomCj 
  with 
  accompanying 
  formation 
  of 
  the 
  spindle, 
  

   in 
  the 
  interior 
  of 
  the 
  nucleus. 
  

  

  Hertwig" 
  has 
  shown 
  that 
  in 
  the 
  reproductive 
  cycle 
  of 
  

   Actinosphferium, 
  a 
  centrosome 
  emerges 
  from 
  the 
  nucleus 
  

   immediately 
  before 
  the 
  polar 
  divisions 
  of 
  the 
  secondary 
  cysts. 
  

   Schaudinn 
  has 
  actually 
  seen 
  intra 
  vitam 
  the 
  centrosome 
  

   escaping 
  from 
  the 
  nucleus 
  in 
  the 
  spore 
  of 
  Acanithocystis. 
  

  

  Lastly, 
  in 
  the 
  primary 
  oocyte 
  Riickert 
  (1894) 
  has 
  asserted 
  

   a 
  similar 
  origin 
  of 
  the 
  centrosomes 
  in 
  Cyclops, 
  while 
  the 
  same 
  

   view 
  has 
  been, 
  though 
  more 
  doubtfully, 
  expressed 
  for 
  other 
  

   forms 
  (Cerebratulus 
  [Coe], 
  Thalassema 
  [Grriffin], 
  Prosthe- 
  

   ceraeus 
  [von 
  Klinckowstrom], 
  Myzostoma 
  [von 
  Kostanecki], 
  

   Asterias 
  [Matthews], 
  Thysanozoon 
  [van 
  der 
  Stricht], 
  Poly- 
  

   choerus 
  [Gardiner], 
  and 
  Cyclas 
  [Stauffacher] 
  ) 
  ; 
  in 
  all 
  these 
  

   cases 
  the 
  centrosomes 
  first 
  appear 
  in 
  invaginations 
  of 
  the 
  

   membrane 
  of 
  the 
  germinal 
  vesicle. 
  

  

  (ii) 
  Structure 
  and 
  functions 
  of 
  the 
  centrosome. 
  

  

  The 
  centrosome 
  is 
  a 
  body 
  which 
  is 
  almost 
  invariably 
  to 
  be 
  

   found 
  during 
  the 
  division 
  of 
  the 
  animal 
  cell. 
  There 
  are, 
  

   however, 
  some 
  exceptions. 
  It 
  is 
  stated 
  by 
  Boveri 
  (1887, 
  

   1890) 
  to 
  be 
  absent 
  from 
  the 
  polar 
  spindles 
  of 
  Ascaris 
  and 
  

   Sagitta. 
  Sobotta 
  has 
  made 
  the 
  same 
  statement 
  of 
  the 
  polar 
  

   spindles 
  of 
  Amphioxus 
  and 
  the 
  Mouse, 
  Brauer 
  and 
  Behrens 
  

   of 
  those 
  of 
  Branchipus 
  and 
  the 
  Trout 
  respectively, 
  and 
  various 
  

   authors 
  (Carnoy, 
  Fick, 
  and 
  myself) 
  of 
  the 
  polar 
  spindles 
  of 
  

   Amphibia. 
  Further, 
  its 
  existence 
  in 
  the 
  cells 
  of 
  the 
  higher 
  

   plants 
  is 
  totally 
  denied 
  by 
  Strasburger 
  and 
  his 
  school. 
  

  

  With 
  regard 
  to 
  all 
  these 
  cases, 
  I 
  venture 
  to 
  make 
  two 
  

   suggestions. 
  As 
  far 
  as 
  the 
  plants 
  are 
  concerned, 
  it 
  is 
  only 
  

   fair 
  to 
  say 
  that 
  Gruignard 
  and 
  many 
  other 
  observers 
  still 
  

   adhere 
  to 
  the 
  opposite 
  view. 
  In 
  the 
  second 
  place, 
  no 
  one 
  will 
  

   pretend 
  that 
  the 
  pole 
  of 
  a 
  spindle 
  is 
  occupied 
  by 
  a 
  Euclidian 
  

   point 
  ; 
  some 
  small 
  particle 
  is 
  undoubtedly 
  there 
  which 
  may 
  be 
  

  

  