﻿284 
  

  

  Mr. 
  L. 
  T. 
  Hogben. 
  

  

  at 
  the 
  posterior 
  pole 
  which 
  condense 
  as 
  in 
  Apanteles 
  to 
  form 
  a 
  polar 
  disc 
  or 
  

   oosoma 
  of 
  crescentic 
  shape 
  (fig. 
  52). 
  

  

  The 
  foregoing 
  account 
  of 
  the 
  oogenesis 
  of 
  an 
  Ichneumonid 
  confirms 
  the 
  

   view 
  that 
  a 
  remarkable 
  similarity 
  exists 
  in 
  the 
  behaviour 
  of 
  the 
  nucleus 
  of 
  

   the 
  oocyte 
  throughout 
  the 
  large 
  families 
  of 
  the 
  parasitic 
  Hymenoptera 
  

   (Chalcididse, 
  Braconidae, 
  Cynipidse, 
  and 
  Ichneumonidse). 
  There 
  can 
  be 
  little 
  

   doubt 
  that 
  the 
  phenomena 
  described 
  are 
  general 
  within 
  the 
  group 
  and 
  

   contrast 
  strongly 
  with 
  the 
  oogenesis 
  of 
  other 
  Insecta 
  and 
  the 
  remaining 
  

   families 
  of 
  Hymenoptera. 
  The 
  most 
  noteworthy 
  features 
  on 
  which 
  attention 
  

   has 
  been 
  focussed 
  are 
  the 
  peculiar 
  interruption 
  of 
  the 
  first 
  polar 
  mitosis 
  and 
  

   the 
  existence 
  of 
  a 
  second 
  syndesis 
  immediately 
  before 
  the 
  formation 
  of 
  the 
  

   maturation 
  spindle. 
  

  

  5. 
  Lasius 
  Flava. 
  

  

  In 
  order 
  to 
  contrast 
  the 
  peculiar 
  phenomena 
  which 
  have 
  been 
  described 
  in 
  

   the 
  oogenesis 
  of 
  the 
  parasitic 
  families 
  of 
  Hymenoptera, 
  it 
  is 
  proposed 
  to 
  

   complete 
  this 
  account 
  with 
  a 
  brief 
  survey 
  of 
  the 
  history 
  of 
  the 
  egg 
  nucleus 
  in 
  

   the 
  yellow 
  ant, 
  Lasius 
  flava, 
  as 
  exemplifying 
  the 
  Aculeata. 
  

  

  Though 
  the 
  maturation 
  of 
  the 
  laid 
  egg 
  and 
  the 
  spermatogenesis 
  of 
  various 
  

   Aculeata 
  have 
  been 
  somewhat 
  extensively 
  studied, 
  the 
  synaptic 
  phase 
  has 
  

   been 
  overlooked 
  by 
  most 
  authors, 
  or 
  at 
  least 
  treated 
  very 
  imperfectly. 
  

   Paulcke 
  (1900) 
  made 
  a 
  study 
  of 
  nuclear 
  differentiation 
  in 
  the 
  ovarioles 
  of 
  

   Apis, 
  and 
  came 
  to 
  the 
  conclusion 
  that 
  all 
  the 
  cell 
  elements 
  are 
  germinal 
  in 
  

   origin, 
  finding 
  no 
  visible 
  distinction 
  between 
  oocytes 
  and 
  nurse 
  cells 
  until 
  

   the 
  zone 
  of 
  synapsis 
  is 
  passed. 
  Nachtsheim's 
  figures 
  are 
  similar. 
  

  

  Towards 
  'the 
  end 
  of 
  pupal 
  life 
  in 
  Lasius 
  all 
  stages 
  of 
  oogenesis 
  can 
  be 
  

   found 
  in 
  the 
  ovarioles, 
  except 
  the 
  full-grown 
  egg. 
  The 
  terminal 
  filaments 
  

   consist 
  of 
  flattened 
  cells 
  with 
  granular 
  nuclei, 
  arranged 
  in 
  horizontal 
  rows 
  

   and 
  extending 
  across 
  the 
  entire 
  width 
  of 
  the 
  tube. 
  At 
  the 
  point 
  of 
  origin 
  of 
  

   the 
  " 
  terminal 
  chamber 
  " 
  mitoses 
  are 
  frequent. 
  In 
  a 
  small 
  number 
  of 
  very 
  

   clear 
  figures, 
  24 
  minute 
  chromosomes 
  were 
  counted. 
  The 
  nuclei 
  of 
  the 
  

   terminal 
  chamber, 
  as 
  in 
  Campanotus, 
  are 
  not 
  limited 
  by 
  cell 
  walls, 
  but 
  from 
  a 
  

   syncytium. 
  In 
  the 
  chamber 
  are 
  found 
  successively 
  (a) 
  rosettes 
  ; 
  (b) 
  a 
  zone 
  of 
  

   synapsis 
  ; 
  (c) 
  a 
  zone 
  of 
  differentiation, 
  where 
  nurse 
  cells 
  and 
  oocytes 
  become 
  

   recognisably 
  distinct. 
  At 
  first 
  the 
  nurse 
  cells 
  and 
  oocytes 
  are 
  indiscriminately 
  

   scattered. 
  In 
  the 
  lower 
  part 
  of 
  the 
  ovariole 
  they 
  are 
  arranged 
  in 
  the 
  charac- 
  

   teristic 
  manner, 
  the 
  oocytes 
  forming 
  an 
  axial 
  series 
  alternating 
  with 
  nurse 
  

   chambers 
  and 
  surrounded 
  by 
  a 
  definite 
  follicular 
  epithelium 
  (fig. 
  57). 
  

  

  The 
  large 
  number 
  and 
  small 
  size 
  of 
  the 
  chromosomes 
  in 
  the 
  Hymenoptera 
  

   generally 
  render 
  the 
  group 
  most 
  unfavourable 
  for 
  a 
  crucial 
  elucidation 
  of 
  the 
  

   synaptic 
  phase, 
  but 
  in 
  studying 
  the 
  ovarioles 
  of 
  Lasius, 
  the 
  more 
  satisfactory 
  

  

  