﻿314 
  

  

  Mr. 
  L. 
  T. 
  Hogben. 
  

  

  " 
  un 
  premier 
  element 
  absolument 
  indispensable 
  a 
  sa 
  solution 
  (the 
  problem 
  of 
  

   numerical 
  reduction) 
  c'est 
  la 
  connaissance 
  approfondie 
  des 
  prophases 
  de 
  la 
  

   mitose 
  somatique," 
  passes 
  on 
  to 
  explain 
  the 
  parallel 
  fusion, 
  so 
  often 
  described, 
  

   in 
  the 
  zygotene 
  stage, 
  in 
  the 
  following 
  terms 
  : 
  " 
  les 
  grosses 
  travels 
  ne 
  se 
  

   forment 
  pas 
  par 
  fusionnement 
  lateral 
  de 
  deux 
  fins 
  filaments, 
  mais 
  se 
  produisent 
  

   de 
  la 
  fagon 
  suivante, 
  certaines 
  travees 
  regoiverit 
  la 
  chromatine 
  qui 
  charge 
  les 
  

   travels 
  sdcondaires 
  .... 
  c'est 
  le 
  parallelisme 
  des 
  filaments 
  chromatiques 
  qui 
  

   produit 
  les 
  images 
  qui 
  ont 
  e'te' 
  interpreters 
  comme 
  un 
  fusionnement 
  lateral 
  de 
  

   chromosomes 
  . 
  . 
  . 
  ." 
  (15). 
  As 
  a 
  statement 
  of 
  fact, 
  this 
  has 
  been 
  sufficiently 
  

   dealt 
  with 
  by 
  Wilson. 
  Let 
  it 
  be 
  admitted 
  nevertheless 
  that 
  " 
  une 
  connais- 
  

   sance 
  approfondie 
  des 
  prophases 
  de 
  la 
  mitose 
  somatique 
  " 
  is 
  an 
  essential 
  

   condition 
  for 
  the 
  correct 
  interpretation 
  of 
  the 
  meiotic 
  phase 
  ; 
  let 
  it 
  be 
  

   conceded, 
  moreover, 
  that 
  many 
  advocates 
  of 
  parasynapsis 
  have 
  paid 
  too 
  little 
  

   attention 
  to 
  such 
  phenomena 
  : 
  on 
  what 
  facts 
  does 
  Duesberg 
  base 
  his 
  com- 
  

   parison 
  of 
  the 
  somatic 
  and 
  maturation 
  prophases 
  ? 
  Obviously, 
  there 
  are 
  

   three 
  valid 
  criteria 
  : 
  similarity 
  in 
  shape, 
  number, 
  and 
  dispositions 
  of 
  the 
  

   chromatin 
  units. 
  As 
  regards 
  the 
  first, 
  nothing 
  could 
  display 
  a 
  more 
  marked 
  

   difference 
  from 
  the 
  gross 
  bacilliform 
  chromosomes 
  of 
  the 
  prophase 
  of 
  a 
  normal 
  

   mitosis 
  and 
  their 
  compact 
  granular 
  precursors 
  in 
  the 
  condensation 
  of 
  the 
  

   reticulum 
  than 
  the 
  attenuated 
  and 
  finely 
  beaded 
  loops 
  seen 
  in 
  the 
  heterotype 
  

   nucleus 
  from 
  its 
  very 
  inception 
  ; 
  there 
  is 
  evidently 
  no 
  basis 
  of 
  comparison 
  

   to 
  be 
  sought 
  in 
  this 
  direction. 
  Turning 
  next 
  to 
  the 
  numerical 
  relations, 
  

   Duesberg 
  disdains 
  to 
  consider 
  the 
  witness 
  of 
  numerous 
  observers 
  to 
  the 
  

   existence 
  of 
  the 
  full 
  diploid 
  number 
  of 
  filaments 
  before 
  synapsis 
  ; 
  it 
  is, 
  there- 
  

   fore, 
  not 
  surprising 
  that 
  he 
  fails 
  to 
  appreciate 
  the 
  dissimilarity 
  of 
  the 
  

   zygotene 
  stage 
  to 
  any 
  phenomenon 
  characteristic 
  of 
  the 
  nuclear 
  history 
  of 
  the 
  

   premeiotic 
  germ 
  cells. 
  When 
  finally 
  the 
  orientation 
  of 
  the 
  bouquet, 
  so 
  

   common 
  in 
  representatives 
  of 
  the 
  most 
  diverse 
  groups 
  of 
  animals 
  (flat 
  worms, 
  

   insects, 
  molluscs, 
  fishes, 
  amphibia, 
  and 
  mammals), 
  is 
  taken 
  into 
  consideration, 
  

   Duesberg 
  can 
  only 
  protest 
  that 
  in 
  a 
  few 
  cases 
  a 
  typical 
  bouquet 
  is 
  absent. 
  

   This 
  is 
  admittedly 
  true 
  ; 
  but 
  to 
  deny 
  a 
  universal 
  polarisation 
  of 
  the 
  zygotene 
  

   filaments 
  does 
  not 
  invalidate 
  the 
  statement 
  that 
  the 
  disposition 
  of 
  the 
  

   chromatin 
  elements 
  in 
  the 
  early 
  stages 
  of 
  the 
  meiotic 
  phase 
  is 
  altogether 
  

   unlike 
  their 
  arrangement 
  in 
  a 
  typical 
  prophase 
  nucleus. 
  In 
  Periplaneta 
  the 
  

   premeiotic 
  and 
  maturation 
  prophases 
  resemble 
  one 
  another 
  neither 
  in 
  the 
  

   form, 
  numerical 
  behaviour, 
  nor 
  disposition 
  of 
  the 
  chromatin 
  units 
  : 
  the 
  

   maturation 
  prophase 
  is 
  quintessentially 
  concerned 
  with 
  bringing 
  about 
  the 
  

   conjugation 
  in 
  pairs 
  of 
  filaments 
  which 
  are 
  individually 
  equivalent 
  to 
  the 
  

   chromosomes 
  of 
  the 
  antepenultimate 
  telophase 
  of 
  the 
  germ 
  cell 
  divisions 
  

   in 
  the 
  individual. 
  

  

  