﻿MATUK'ATION, 
  KTC, 
  OF 
  THE 
  KGG 
  OF 
  THI'] 
  AXOLOTL. 
  455 
  

  

  formation 
  of 
  the 
  second 
  polar 
  body 
  (Castle 
  [Cioua] 
  , 
  Coe 
  and 
  

   von 
  Kostanecki 
  [Cerebratulus], 
  G-riffin 
  [Thalasseraa 
  and 
  

   ZirpliEea] 
  ^ 
  Foot 
  [Allolobopliora], 
  Lillie 
  [Unio], 
  etc.), 
  Wheeler 
  

   has 
  stated 
  that 
  in 
  Myzostoma 
  not 
  only 
  do 
  they 
  persist 
  but 
  

   alone 
  are 
  concerned 
  in 
  the 
  production 
  of 
  the 
  fertilisation 
  

   spindle. 
  " 
  I 
  have 
  never 
  been 
  able/' 
  says 
  this 
  author, 
  "to 
  find 
  

   any 
  traces 
  of 
  such 
  archoplasm 
  or 
  any 
  centrosome 
  in 
  connec- 
  

   tion 
  with 
  the 
  male 
  pronucleus." 
  This 
  account 
  is, 
  however, 
  

   conti"adicted 
  by 
  von 
  Kostanecki 
  (1898), 
  who, 
  while 
  fully 
  

   admitting 
  the 
  prolonged 
  persistence 
  of 
  the 
  egg-centres, 
  

   claims 
  to 
  have 
  discovered 
  two 
  centrosomes 
  in 
  proximity 
  to 
  

   the 
  sperm-nucleus, 
  and 
  to 
  have 
  seen 
  the 
  formation 
  of 
  the 
  

   fertilisation 
  spindle 
  from 
  these. 
  He 
  admits, 
  however, 
  that 
  

   the 
  verdict 
  must 
  ultimately 
  be 
  given 
  on 
  " 
  die 
  Analogie 
  mit 
  

   deni 
  Befruchtungsvorgang 
  bei 
  anderen 
  Thierspecies.^' 
  

  

  While 
  no 
  one 
  except 
  Wheeler 
  has 
  denied 
  to 
  the 
  sperm- 
  

   centres 
  some 
  share 
  in 
  fertilisation, 
  Conklin 
  and 
  others 
  have 
  

   revived 
  FoFs 
  almost 
  forgotten 
  '^ 
  Quadrille 
  des 
  centres." 
  

   Conklin 
  described 
  this 
  in 
  Crepidula, 
  but 
  in 
  a 
  subsequent 
  

   paper 
  contradicted 
  his 
  earlier 
  account. 
  His 
  later 
  view 
  is 
  that 
  

   the 
  sperm 
  and 
  egg-asters 
  fuse 
  and 
  that 
  then 
  the 
  combination- 
  

   nster 
  divides, 
  the 
  cleavage 
  centrosomes 
  arising 
  within 
  the 
  

   daughter-asters 
  in 
  a 
  manner 
  which 
  is 
  not 
  further 
  determined. 
  

   Blanc 
  has 
  made 
  a 
  somewhat 
  similar 
  assertion 
  for 
  the 
  Trout, 
  

   but 
  he 
  is 
  contradicted 
  by 
  Behrens 
  ; 
  while 
  van 
  der 
  Stricht's 
  

   figures 
  of 
  the 
  " 
  Quadrille 
  " 
  in 
  Amphioxus 
  are 
  shown 
  by 
  

   Sobotta 
  to 
  be 
  really 
  taken 
  from 
  polyspermatic 
  ova. 
  

  

  (ii) 
  Origin 
  of 
  the 
  cleavage 
  centrosome 
  not 
  determined. 
  

  

  In 
  Arenicola 
  (Child), 
  Allolobophora 
  (Foot), 
  Pleurophyl- 
  

   lidia 
  (MacFarland), 
  Unio 
  (Lillie), 
  Prosthecereeus 
  (von 
  

   Klinckowstrom), 
  Polystomuin 
  (Halkin), 
  Insects 
  (Henking), 
  

   and 
  Cerebratulus 
  (Coe), 
  the 
  sperm-asters 
  and 
  centres 
  disap- 
  

   pear 
  : 
  the 
  cleavage 
  centi-osomes 
  then 
  arise 
  de 
  novo. 
  In 
  

   some 
  cases 
  (Cerebratulus, 
  Allolobophora, 
  Unio) 
  they 
  ai-e 
  first 
  

  

  VOL. 
  48, 
  PART 
  3, 
  NEW 
  SERIES. 
  33 
  

  

  