﻿410 
  R. 
  T. 
  Young, 
  

  

  is 
  afforded 
  by 
  the 
  abortive 
  mitoses 
  in 
  gametogenesis 
  and 
  by 
  its 
  in- 
  

   frequent 
  and 
  irregular 
  occurrence 
  elsewhere. 
  

  

  There 
  is 
  very 
  strong 
  evidence 
  that 
  amitosis 
  occasionally 
  occurs, 
  

   while 
  nuclear 
  development 
  from 
  chromidia 
  is 
  probable. 
  De 
  novo 
  

   formation 
  may 
  occur, 
  but 
  there 
  is 
  no 
  positive 
  evidence 
  of 
  it 
  in 
  these 
  

   organs. 
  

  

  The 
  development 
  of 
  the 
  sex 
  cells 
  is 
  much 
  abbreviated; 
  polar 
  

   bodies 
  are 
  not 
  formed, 
  and 
  the 
  structure 
  of 
  the 
  sperms 
  is 
  apparently 
  

   very 
  simple. 
  

  

  A 
  yolk 
  cell 
  is 
  attached 
  to 
  the 
  oocyte 
  in 
  the 
  oviduct 
  or 
  the 
  

   uterus. 
  

  

  Early 
  cleavage 
  follows 
  two 
  types: 
  in 
  the 
  first 
  a 
  fusion 
  nucleus 
  

   divides 
  amitotically, 
  in 
  the 
  second 
  the 
  pronuclei 
  break 
  up 
  before 
  

   fusion 
  to 
  form 
  the 
  cleavage 
  nuclei. 
  

  

  