﻿326 
  

  

  Mr. 
  L. 
  T. 
  Hogben. 
  

  

  stages 
  ; 
  no 
  data 
  respecting 
  these 
  stages 
  in 
  the 
  oocyte, 
  where 
  they 
  are 
  

   particularly 
  clear; 
  and, 
  finally 
  an 
  incomplete 
  series 
  showing 
  the 
  critical 
  stages 
  

   in 
  heterotype 
  metaphase 
  of 
  preparations 
  fixed 
  with 
  Flemming's 
  reagent. 
  An 
  

   account 
  of 
  telosynapsis 
  in 
  the 
  closely 
  allied 
  Plecoptera 
  has 
  recently 
  been 
  

   published 
  by 
  Nakahara, 
  1919 
  (28) 
  ; 
  the 
  material 
  was 
  partly 
  fixed 
  in 
  Bouin 
  ; 
  it 
  

   is 
  implied 
  that 
  only 
  adult 
  testes 
  were 
  employed 
  ; 
  and 
  it 
  is, 
  therefore, 
  not 
  

   surprising 
  that 
  typical 
  early 
  stages 
  are 
  lacking, 
  while 
  the 
  evidence 
  regarding 
  

   the 
  first 
  division 
  is 
  clearly 
  fragmentary. 
  For 
  a 
  full 
  discussion 
  of 
  Orthopteran 
  

   gametogenesis 
  the 
  reader 
  is 
  referred 
  to 
  the 
  excellent 
  review 
  of 
  the 
  subject 
  by 
  

   McClung 
  (29), 
  who 
  expresses 
  no 
  judgment 
  on 
  the 
  original 
  method 
  by 
  which 
  

   homologous 
  chromosomes 
  are 
  brought 
  into 
  association. 
  Apart 
  from 
  the 
  work 
  

   of 
  Nakahara, 
  one 
  other 
  recent 
  communication 
  in 
  part 
  adheres 
  to 
  the 
  telo- 
  

   synaptic 
  interpretation 
  of 
  the 
  Orthopteran 
  tetrad. 
  According 
  to 
  Payne, 
  1914 
  

   (33), 
  some 
  of 
  the 
  rings 
  in 
  Forficula 
  are 
  transformed 
  in 
  the 
  manner 
  described 
  

   by 
  Farmer 
  and 
  Moore, 
  Sutton, 
  Davis 
  and 
  other 
  pioneer 
  workers 
  ; 
  while 
  others 
  

   conform 
  to 
  the 
  mode 
  described 
  here 
  as 
  also 
  by 
  the 
  list 
  of 
  authors 
  quoted 
  

   above. 
  Such 
  a 
  view 
  makes 
  the 
  earlier 
  events 
  of 
  synapsis 
  so 
  unintelligible 
  

   as 
  to 
  amount 
  to 
  a 
  practical 
  denial 
  of 
  synapsis. 
  In 
  the 
  light 
  of 
  the 
  data 
  given 
  

   above 
  regarding 
  the 
  a 
  and 
  a' 
  chromosomes, 
  as 
  well 
  as 
  for 
  the 
  consideration 
  

   stated, 
  it 
  is 
  hardly 
  possible 
  to 
  accept 
  Payne's 
  conclusion 
  unreservedly 
  until 
  

   confirmed. 
  

  

  Summary. 
  

  

  (1) 
  Oogenesis 
  and 
  spermatogenesis 
  in 
  Periplaneta 
  have 
  been 
  studied, 
  the 
  

   former 
  for 
  the 
  first 
  time 
  ; 
  special 
  attention 
  has 
  been 
  paid 
  to 
  the 
  events 
  of 
  

   the 
  telophase 
  in 
  its 
  bearing 
  on 
  the 
  relation 
  of 
  the 
  events 
  of 
  the 
  meiotic 
  

   phase 
  in 
  animals 
  and 
  plants 
  respectively. 
  

  

  (2) 
  The 
  chromosomes 
  do 
  not 
  divide 
  in 
  the 
  premeiotic 
  mitoses, 
  as 
  they 
  pass 
  

   to 
  the 
  polar 
  ends 
  of 
  the 
  spindle 
  ; 
  in 
  the 
  telophase, 
  they 
  become 
  attenuated 
  

   before 
  passing 
  into 
  the 
  reticulate 
  condition, 
  but 
  do 
  not 
  display 
  any 
  evidence 
  

   of 
  cleavage. 
  

  

  (3) 
  The 
  splitting 
  of 
  individual 
  chromosomes 
  begins 
  in 
  the 
  prophase, 
  the 
  

   separation 
  of 
  the 
  halves 
  being 
  a 
  process 
  of 
  progressive 
  differentiation 
  ; 
  

   cleavage 
  is 
  completed 
  before 
  they 
  adopt 
  the 
  equatorial 
  position 
  in 
  the 
  

   metaphase. 
  

  

  (4) 
  Metaphase 
  counts 
  confirmed 
  Morse's 
  contention 
  that 
  there 
  are 
  two 
  

   accessory 
  chromosomes 
  in 
  the 
  female 
  cells 
  and 
  an 
  unpaired 
  heterochromosome 
  

   in 
  the 
  male. 
  

  

  (5) 
  Oogenesis 
  in 
  Periplaneta 
  offers 
  much 
  more 
  favourable 
  conditions 
  for 
  

   a 
  study 
  of 
  the 
  earlier 
  events 
  of 
  synapsis 
  than 
  spermatogenesis, 
  but 
  in 
  

   essentials 
  the 
  processes 
  are 
  similar, 
  with 
  the 
  exception 
  of 
  the 
  fact 
  that 
  the 
  

  

  