﻿Studies 
  on 
  Synapsis. 
  

  

  273 
  

  

  capacity 
  greatly 
  decreases, 
  shows 
  18-20 
  chromosomes 
  on 
  the 
  equatorial 
  

   plate 
  of 
  the 
  first 
  segmentation 
  division. 
  Segmentation 
  mitoses 
  showed 
  the 
  

   same 
  number. 
  Schleip 
  reinvestigated 
  the 
  cytology 
  of 
  the 
  egg 
  in 
  Rhodites 
  in 
  

   1909. 
  He 
  gives 
  the 
  number 
  of 
  chromosomes 
  in 
  the 
  young 
  oocyte 
  as 
  10-12, 
  

   and 
  denies 
  that 
  those 
  of 
  the 
  female 
  pronucleus 
  are 
  doubled 
  before 
  the 
  first 
  

   cleavage, 
  finding 
  that 
  the 
  segmentation 
  mitoses 
  show 
  12 
  chromosomes. 
  

   He 
  concludes 
  that 
  there 
  is 
  no 
  reduction 
  in 
  Rhodites, 
  though 
  polar 
  bodies 
  are 
  

   formed, 
  i.e., 
  the 
  maturation 
  mitoses 
  are 
  equational. 
  In 
  heavily 
  yolked 
  eggs 
  

   where 
  the 
  number 
  of 
  chromosomes 
  is 
  small, 
  the 
  segmentation 
  divisions 
  do 
  

   not 
  afford 
  the 
  most 
  profitable 
  basis 
  for 
  a 
  study 
  of 
  the 
  chromosome 
  cycle, 
  

   and, 
  unhappily, 
  neither 
  of 
  these 
  investigators 
  has 
  added 
  to 
  his 
  work 
  data 
  

   respecting 
  the 
  one 
  point 
  which 
  would 
  give 
  most 
  weight 
  to 
  the 
  results 
  

   obtained, 
  namely, 
  the 
  number 
  of 
  chromosomes 
  in 
  the 
  oogonial 
  mitoses. 
  In 
  

   the 
  present 
  research, 
  the 
  somatic 
  and 
  oogonial 
  mitoses 
  of 
  the 
  larval 
  and 
  

   pupal 
  stages 
  have 
  been 
  thoroughly 
  investigated, 
  and 
  the 
  history 
  of 
  the 
  

   oocyte, 
  from 
  its 
  origin 
  to 
  the 
  time 
  of 
  laying, 
  has 
  been 
  worked 
  out 
  for 
  the 
  

   first 
  time. 
  

  

  The 
  Somatic 
  Mitoses. 
  

  

  It 
  has 
  already 
  been 
  mentioned 
  that 
  neither 
  Henking 
  nor 
  Schleip 
  com- 
  

   menced 
  their 
  investigations 
  on 
  the 
  chromosome 
  cycle 
  of 
  Rhodites 
  by 
  a 
  study 
  

   of 
  the 
  mitoses 
  in 
  the 
  larval 
  or 
  pupal 
  stages, 
  in 
  which 
  the 
  oogonia 
  are 
  to 
  be 
  

   found 
  dividing. 
  As 
  pupation 
  is 
  rapidly 
  completed 
  in 
  Rhodites, 
  the 
  task 
  of 
  

   finding 
  nuclei 
  in 
  division 
  during 
  the 
  early 
  stages 
  is 
  not 
  a 
  difficult 
  one. 
  In 
  

   sections 
  cut 
  from 
  material 
  fixed 
  in 
  the 
  inception 
  of 
  pupal 
  life, 
  mitoses 
  are 
  

   abundant 
  in 
  the 
  developing 
  wing 
  epithelia, 
  nervous 
  system, 
  and 
  follicle 
  cells. 
  

   In 
  all 
  cases 
  the 
  number 
  of 
  chromosomes 
  is 
  at 
  least 
  18 
  ; 
  Henking 
  gave 
  18-20 
  

   for 
  the 
  segmentation 
  mitoses, 
  and 
  an 
  element 
  of 
  uncertainty 
  must 
  be 
  

   conceded 
  in 
  virtue 
  of 
  the 
  extremely 
  minute 
  dimensions 
  of 
  the 
  chromosomes 
  

   in 
  Rhodites 
  as 
  compared, 
  e.g., 
  with 
  Neuroterus, 
  or, 
  more 
  particularly, 
  with 
  

   Cynips. 
  The 
  existence 
  of 
  18 
  chromosomes 
  in 
  the 
  dividing 
  nuclei 
  of 
  the 
  

   somatic 
  tissues 
  is 
  not 
  conclusive 
  evidence 
  that 
  the 
  same 
  number 
  occurs 
  in 
  

   the 
  germ 
  cells 
  ; 
  in 
  Apis, 
  the 
  somatic 
  mitoses 
  of 
  the 
  male 
  show 
  four 
  times 
  the 
  

   number 
  of 
  chromosomes 
  displayed 
  by 
  the 
  segmenting 
  spermatogonia, 
  and 
  in 
  

   Neuroterus 
  they 
  display 
  the 
  number 
  20 
  (characteristic 
  of 
  the 
  female) 
  in 
  both 
  

   sexes, 
  while 
  spermatogonial 
  counts 
  give 
  half 
  this 
  number. 
  Nevertheless, 
  the 
  

   follicle 
  cells 
  in 
  the 
  ovaries 
  present 
  another 
  case. 
  Follicular 
  cells 
  have 
  

   frequently 
  been 
  described 
  as 
  dividing 
  amitotically 
  in 
  insects; 
  in 
  some 
  cases, 
  

   as 
  in 
  the 
  predogenetic 
  Cecidomyid 
  Miastor, 
  oocytes 
  alone 
  are 
  truly 
  germinal 
  

   in 
  origin. 
  In 
  the 
  Hymenoptera 
  the 
  follicle 
  cells 
  divide 
  normally, 
  and 
  it 
  has 
  

   been 
  well 
  established 
  by 
  the 
  work 
  of 
  Korschelt 
  (1886), 
  Paulcke 
  (1907), 
  and 
  

  

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