﻿536 
  J. 
  BBETLAND 
  FARMER 
  AND 
  J. 
  E. 
  S. 
  MOOEE. 
  

  

  we 
  have 
  the 
  chromosomes 
  in 
  the 
  form 
  of 
  small 
  rings 
  which 
  

   divide 
  in 
  the 
  manner 
  represented 
  in 
  figs. 
  74, 
  75 
  ; 
  in 
  the 
  

   other 
  the 
  ring 
  is 
  open 
  at 
  one 
  side, 
  or 
  is 
  a 
  loop, 
  and 
  being 
  

   attached 
  to 
  the 
  spindle 
  in 
  the 
  fashion 
  shown 
  in 
  fig. 
  77, 
  opens 
  

   out 
  in 
  the 
  manner 
  represented. 
  In 
  this 
  latter 
  variation 
  

   the 
  final 
  condition 
  of 
  the 
  dividing 
  chromosomes 
  is 
  extremely 
  

   interesting; 
  for 
  the 
  original 
  longitudinal 
  split 
  can 
  be 
  traced 
  

   with 
  great 
  clearness, 
  and 
  can 
  actually 
  be 
  watched 
  as 
  it 
  forms 
  

   the 
  characteristic 
  longitudinal 
  split 
  of 
  the 
  daughter 
  chromo- 
  

   somes 
  of 
  the 
  first 
  maiotic 
  (heterotype) 
  division 
  first 
  described 
  

   by 
  Flemming, 
  in 
  the 
  salamander, 
  among 
  animals, 
  and 
  by 
  Stras- 
  

   burger, 
  in 
  Tradescantia, 
  among 
  plants. 
  From 
  such 
  figures 
  

   in 
  the 
  cockroach 
  it 
  becomes 
  at 
  once 
  obvious 
  that 
  this 
  singular 
  

   and 
  well-known 
  split 
  condition 
  of 
  the 
  daughter 
  chromosomes 
  

   of 
  the 
  first 
  maiotic 
  (heterotype) 
  division, 
  to 
  which 
  the 
  above 
  

   authors 
  long 
  since 
  drew 
  attention 
  without 
  offering 
  any 
  

   explanation, 
  is 
  nothing 
  more 
  nor 
  less 
  than 
  the 
  persistence 
  in 
  

   these 
  daughter 
  elements 
  of 
  the 
  original 
  longitudinal 
  split 
  of 
  

   the 
  synaptic 
  spirem 
  thread. 
  

  

  From 
  the 
  above 
  it 
  will 
  have 
  become 
  obvious 
  that 
  in 
  the 
  

   cockroach 
  the 
  first 
  maiotic 
  (heterotype) 
  division 
  differs 
  from 
  

   the 
  pre-maiotic 
  divisions 
  which 
  have 
  anteceded 
  it 
  in 
  this 
  ; 
  

   that 
  here, 
  instead 
  of 
  the 
  chromosomes 
  consisting 
  of 
  thirty-two 
  

   split 
  rods 
  or 
  lengths 
  of 
  the 
  spirem 
  thread 
  the 
  halves 
  of 
  

   which 
  will 
  be 
  distributed 
  between 
  the 
  daughter 
  cells, 
  we 
  find 
  

   that 
  the 
  spirem 
  thread-work 
  tends 
  at 
  first 
  to 
  separate 
  into 
  

   only 
  lialf 
  as 
  many 
  lengtlis, 
  that 
  eventually 
  the 
  full 
  somatic 
  

   number 
  of 
  elements 
  are 
  formed, 
  but 
  these 
  remain 
  associated 
  

   together 
  in 
  parts 
  to 
  form 
  the 
  potentially 
  double 
  heterotype. 
  

   chromosomes 
  ; 
  or, 
  in 
  other 
  words, 
  the 
  first 
  maiotic 
  division 
  is 
  

   distinguished 
  from 
  the 
  pre-maiotic 
  divisions 
  by 
  the 
  temporary 
  

   union 
  of 
  the 
  pre-maiotic 
  chromosomes 
  in 
  pairs, 
  and 
  by 
  the 
  

   simple 
  separation 
  of 
  these 
  elements 
  during 
  the 
  ensuing 
  mitosis. 
  

   In 
  this 
  way 
  the 
  cells 
  of 
  the 
  second 
  maiotic 
  generation 
  receive 
  

   only 
  half 
  the 
  number 
  of 
  chromosomes 
  which 
  have 
  chai-acterised 
  

   the 
  preceding 
  generations. 
  Nevertheless, 
  in 
  the 
  diascliistic 
  

   (heterotype) 
  prophase 
  the 
  thread-work 
  is 
  longitudinally 
  split, 
  

  

  