﻿Studies 
  on 
  Synapsis. 
  

  

  325 
  

  

  the 
  segmentation 
  of 
  the 
  ring-like 
  heterotype 
  chromosomes 
  transversely 
  is 
  

   brought 
  about 
  by 
  the 
  separation 
  of 
  the 
  diplotene 
  threads 
  longitudinally 
  

   for 
  all 
  cases 
  alike. 
  

  

  Great 
  importance 
  is 
  attached 
  to 
  the 
  retarded 
  division 
  of 
  the 
  a 
  and 
  a 
  , 
  

   chi 
  omosomes, 
  since 
  their 
  behaviour 
  emphasises 
  how 
  easy 
  it 
  is 
  to 
  read 
  the 
  

   sequence 
  of 
  events 
  in 
  the 
  heterotype 
  metaphase 
  in 
  the 
  wrong 
  order 
  unless 
  

   the 
  attempt 
  is 
  made 
  to 
  follow 
  the 
  genesis 
  of 
  each 
  unit 
  separately. 
  ISTo 
  doubt 
  

   it 
  is 
  for 
  this 
  reason 
  that 
  the 
  erroneous 
  telosynaptic 
  description 
  of 
  the 
  direct 
  

   formation 
  of 
  rings 
  from 
  loops 
  by 
  transverse 
  division 
  of 
  the 
  diplotene 
  threads 
  

   has 
  arisen. 
  

  

  Eegarding 
  the 
  second 
  maturation 
  divisions 
  of 
  the 
  male 
  germ 
  cells 
  there 
  is 
  

   nothing 
  to 
  add 
  to 
  previous 
  work, 
  since 
  it 
  is 
  agreed 
  by 
  all 
  that 
  the 
  second 
  

   division 
  is 
  equational. 
  This 
  does 
  not 
  necessarily 
  imply 
  that 
  reduction 
  is 
  

   effected 
  in 
  the 
  heterotype 
  mitosis 
  ; 
  for 
  so 
  far 
  as 
  the 
  male 
  is 
  concerned 
  there 
  is 
  

   no 
  evidence 
  that 
  the 
  line 
  of 
  separation 
  of 
  the 
  diplotene 
  components 
  

   corresponds 
  to 
  the 
  plane 
  in 
  which 
  the 
  leptotene 
  filaments 
  approximate 
  in 
  

   synapsis. 
  It 
  is 
  believed, 
  however, 
  that 
  this 
  is 
  definitely 
  the 
  case 
  in 
  the 
  

   oocyte. 
  The 
  point 
  is 
  really 
  very 
  important 
  ; 
  if, 
  and 
  only 
  if, 
  data 
  respecting 
  

   pre- 
  or 
  post-reduction 
  are 
  available, 
  can 
  the 
  process 
  of 
  gametic 
  segregation 
  

   be 
  demonstrated 
  directly. 
  On 
  the 
  evidence 
  submitted 
  it 
  would 
  appear 
  : 
  

   (a) 
  that 
  the 
  filaments 
  which 
  conjugate 
  side 
  by 
  side 
  in 
  the 
  bouquet 
  stage 
  

   correspond 
  to 
  whole 
  premeiotic 
  chromosomes 
  ; 
  (b) 
  that 
  the 
  maturation 
  divisions 
  

   are 
  of 
  such 
  a 
  type 
  as 
  to 
  provide 
  for 
  a 
  segregation 
  of 
  alternate 
  components 
  of 
  

   the 
  bivalents 
  so 
  constituted. 
  Eespecting 
  the 
  further 
  question 
  of 
  the 
  relation 
  

   of 
  the 
  heterotype 
  chromosomes 
  to 
  the 
  biparental 
  complex 
  of 
  the 
  zygote 
  no 
  

   data 
  are 
  submitted 
  ; 
  and 
  the 
  reality 
  of 
  synapsis 
  will 
  not, 
  therefore, 
  be 
  

   discussed. 
  The 
  conclusions 
  here 
  advocated 
  are 
  in 
  harmony 
  with 
  those 
  of 
  other 
  

   recent 
  workers 
  on 
  Orthopteran 
  chromosomes, 
  namely: 
  Wenrich, 
  1917(22), 
  

   Gdrard 
  (23), 
  Eobertson, 
  1915 
  (24), 
  working 
  on 
  Acrididae 
  ; 
  Otte, 
  1907 
  (25; 
  and 
  

   Mohr, 
  1915 
  on 
  the 
  Locustidae 
  ; 
  Stevens, 
  1912 
  (26) 
  on 
  Centophilus; 
  also 
  

   Eobertson 
  on 
  Tettigidse 
  and 
  Yejdovsky, 
  1912 
  on 
  locustids. 
  Further 
  it 
  may 
  

   be 
  said 
  that 
  Baumgartner's 
  figures 
  of 
  the 
  metamorphosis 
  of 
  the 
  heterotype 
  

   chromosomes 
  in 
  G-ryllus 
  likewise 
  suggest 
  an 
  original 
  parasynaptic 
  union 
  (30). 
  

  

  "With 
  respect 
  to 
  the 
  problem 
  of 
  synapsis 
  in 
  the 
  Orthoptera, 
  it 
  may 
  be 
  said 
  

   that 
  no 
  group 
  has 
  provoked 
  more 
  controversy 
  ; 
  but 
  while 
  divergence 
  exists 
  to 
  a 
  

   very 
  great 
  extent, 
  it 
  must 
  be 
  remembered 
  that 
  the 
  bulk 
  of 
  the 
  work 
  is 
  con- 
  

   cerned 
  mainly 
  with 
  chromosomal 
  individuality 
  and 
  the 
  Accessories; 
  few 
  authors 
  

   like 
  Wenrich 
  and 
  the 
  present 
  writer 
  have 
  set 
  out 
  primarily 
  to 
  investigate 
  

   the 
  mode 
  of 
  synapsis. 
  Hence 
  the 
  conclusions 
  that 
  have 
  been 
  expressed 
  have 
  

   been 
  based 
  too 
  often 
  on 
  an 
  inadequate 
  supply 
  of 
  material 
  showing 
  the 
  earlier 
  

  

  vol. 
  xci. 
  — 
  b. 
  2 
  c 
  

  

  