﻿MAT[JRATI()N, 
  ErC, 
  OF 
  THE 
  EGG 
  OP 
  THK 
  AXOLOTL. 
  445 
  

  

  cytoplasm. 
  The 
  fovination 
  of 
  the 
  yolk 
  seems 
  indeed 
  to 
  be 
  

   intimately 
  related 
  to 
  the 
  solution 
  of 
  the 
  chromatin, 
  for 
  some 
  

   of 
  this 
  dissolved 
  substance 
  passes 
  through 
  the 
  nuclear 
  

   membrane 
  and 
  contributes 
  to 
  the 
  nuclein 
  which 
  can 
  be 
  

   demonstrated 
  in 
  the 
  \"olk. 
  It 
  is 
  during- 
  these 
  processes 
  of 
  

   disintegration 
  that 
  the 
  figures 
  are 
  produced 
  which 
  have 
  beer, 
  

   mistaken 
  by 
  Born 
  and 
  Eiickert 
  for 
  chromosomes. 
  

  

  At 
  the 
  time 
  of 
  maturation 
  the 
  nuclear 
  membrane 
  disappears 
  

   and 
  some 
  of 
  the 
  chromatic 
  nucleoli 
  are 
  used 
  in 
  the 
  production 
  

   of 
  the 
  chroinosomes 
  in 
  a 
  very 
  complicated 
  fashion. 
  According 
  

   to 
  Carnoy 
  the 
  resulting 
  division 
  is 
  longitudinal, 
  but 
  I 
  think 
  it 
  

   must 
  be 
  conceded 
  that 
  when, 
  as 
  here, 
  there 
  is 
  no 
  spireme 
  stage, 
  

   when 
  the 
  chromosomes 
  are 
  formed 
  from 
  round 
  nucleoli, 
  it 
  is 
  

   almost 
  idle 
  to 
  attempt 
  to 
  distinguish 
  between 
  a 
  longitudinal 
  

   and 
  a 
  transverse 
  division. 
  

  

  It 
  will 
  be 
  convenient 
  to 
  discuss 
  briefly 
  at 
  this 
  point 
  two 
  

   questions 
  which 
  are 
  raised 
  by 
  the 
  subsequent 
  behaviour 
  of 
  the 
  

   pronuclei. 
  The 
  first 
  relates 
  to 
  the 
  theory 
  of 
  the 
  persistent 
  

   individuality 
  of 
  the 
  chromosomes. 
  

  

  I 
  have 
  found 
  no 
  evidence 
  in 
  my 
  preparations 
  and 
  very 
  little 
  

   in 
  the 
  literature 
  in 
  support 
  of 
  this 
  assumption. 
  Carnoy's 
  

   account 
  of 
  the 
  histor}^ 
  of 
  the 
  chromatin 
  is, 
  of 
  course, 
  dia- 
  

   metrically 
  opposed 
  to 
  it. 
  

  

  The 
  second 
  question 
  is 
  the 
  formation 
  of 
  a 
  segmentation 
  

   nucleus. 
  This 
  has 
  been 
  seen 
  in 
  Elasmobranchs 
  (Riickert 
  

   [1891, 
  1899]), 
  the 
  Trout 
  (Behrens), 
  Petromyzon, 
  Amphioxus 
  

   (Sobotta 
  [1897]), 
  Cerebratulus 
  (Coe), 
  Prosthiostomum, 
  

   Thalassema, 
  Toxopneustes, 
  and 
  Ciona 
  (Castle, 
  but 
  not 
  Boveri 
  

   [1890]). 
  

  

  In 
  other 
  cases 
  the 
  chromosomes 
  arise 
  from 
  the 
  two 
  pro- 
  

   nuclei 
  in 
  two 
  separate 
  groups. 
  

  

  The 
  distinction, 
  however, 
  seems 
  to 
  be 
  worth 
  little 
  ; 
  Boveri 
  

   (1890) 
  has 
  shown 
  that 
  in 
  Echinus 
  microtuberculatus 
  

   both 
  modes 
  may 
  occur, 
  Michaelis 
  has 
  described 
  one 
  mode, 
  

   myself 
  the 
  other 
  in 
  Triton, 
  and 
  Sobotta 
  (1895) 
  found 
  in 
  the 
  

   Mouse 
  one 
  isolated 
  case 
  of 
  a 
  segmentation 
  nucleus. 
  

  

  