﻿3S 
  

  

  H. 
  S. 
  Pratt, 
  

  

  propria 
  and 
  passes 
  into 
  the 
  uterus. 
  I 
  did 
  not 
  observe 
  tlie 
  extrusion 
  

   of 
  the 
  polar 
  bodies. 
  

  

  It 
  will 
  be 
  interesting, 
  now, 
  to 
  compare 
  the 
  ovarioles 
  and 
  egg- 
  

   follicles 
  of 
  Melophagus 
  with 
  tliose 
  of 
  other 
  insects. 
  As 
  is 
  well 
  known 
  

   Korschelt 
  (9) 
  following 
  Lubbock 
  (13), 
  Leydig 
  (11), 
  and 
  others, 
  has 
  

   sbown 
  that 
  the 
  indifferent, 
  germinal 
  cells 
  in 
  the 
  germarium 
  differ- 
  

   entiate 
  in 
  the 
  youngest 
  follicle 
  into 
  the 
  follieular 
  epithelial 
  cells, 
  the 
  

   ovum, 
  and 
  the 
  nutritive 
  cells 
  if 
  these 
  be 
  present. 
  My 
  own 
  observa- 
  

   tions 
  on 
  Melophagus, 
  as 
  will 
  already 
  have 
  been 
  noticed, 
  clearly 
  con- 
  

   firrn 
  this 
  view. 
  These 
  investigations, 
  purely 
  anatomical 
  in 
  character, 
  

   do 
  not, 
  however, 
  stand 
  in 
  harrnony 
  with 
  the 
  results 
  of 
  the 
  embryo- 
  

   logical 
  investigations 
  of 
  Heymons 
  (8) 
  and 
  Wheeler 
  (22) 
  on 
  certain 
  

   Orthoptera. 
  These 
  authors 
  have 
  found 
  that 
  the 
  follieular 
  epithelial 
  

   cells 
  and 
  the 
  ova 
  in 
  this 
  group 
  of 
  insects, 
  are 
  separate 
  and 
  distinet 
  

   from 
  each 
  other 
  frorn 
  the 
  time 
  of 
  their 
  ineeption 
  in 
  the 
  mesoderrnic 
  

   somites 
  of 
  the 
  enibryo, 
  so 
  that 
  there 
  can 
  be 
  no 
  indifferent 
  germ-cells 
  

   in 
  the 
  germarium. 
  In 
  the 
  Orthoptera. 
  however, 
  the 
  germarium 
  of 
  the 
  

   adult 
  insect 
  is 
  exceedingly 
  small: 
  it 
  may, 
  in 
  fact, 
  be 
  said 
  hardly 
  to 
  

   exist 
  at 
  all 
  in 
  the 
  same 
  sense 
  as 
  in 
  the 
  higher 
  insects. 
  It 
  certainly 
  

   does 
  not 
  contain 
  indifferent 
  cells. 
  Judging 
  from 
  the 
  figures 
  of 
  

   Korschelt 
  (Figs. 
  1 
  — 
  7), 
  the 
  short 
  germarium 
  contains 
  two 
  kinds 
  of 
  

   cells 
  throughout 
  its 
  entire 
  extent, 
  the 
  large 
  ova 
  within 
  and 
  the 
  

   smaller 
  follieular 
  cells 
  on 
  the 
  periphery 
  which 
  are 
  continuous 
  with 
  

   the 
  follieular 
  epithelium 
  of 
  the 
  remainder 
  of 
  the 
  ovariole. 
  In 
  the 
  

   upper 
  end 
  of 
  the 
  germarium 
  there 
  is 
  a 
  small 
  agglomeration 
  of 
  the 
  

   smaller 
  cells, 
  and 
  they 
  alone 
  are 
  found 
  in 
  the 
  terminal 
  thread. 
  In 
  

   the 
  higher 
  insects, 
  on 
  the 
  other 
  hand, 
  a 
  voluminous 
  germarium 
  is 
  

   usually 
  present, 
  and 
  it 
  contains 
  apparently 
  indifferent 
  cells 
  which 
  

   develop 
  into 
  follieular, 
  nutritive, 
  and 
  egg-cells. 
  It 
  is 
  my 
  opinion, 
  

   however, 
  that 
  further 
  investigation 
  in 
  the 
  embryology 
  of 
  the 
  holo- 
  

   metabolic 
  insects 
  will 
  show 
  that 
  in 
  them 
  also 
  the 
  germinal 
  and 
  fol- 
  

   lieular 
  cells 
  are 
  separate 
  and 
  distinet 
  from 
  their 
  ineeption 
  and 
  that 
  

   in 
  some 
  forms 
  the 
  adults 
  will 
  be 
  found 
  to 
  possess 
  a 
  germarium 
  con- 
  

   sisting 
  of 
  two 
  kinds 
  of 
  cells 
  instead 
  of 
  indifferent 
  cells. 
  

  

  Insect 
  ovaries 
  are 
  divided 
  by 
  Korschelt 
  (9) 
  and 
  most 
  of 
  the 
  

   text-books 
  into 
  two 
  classes, 
  those 
  in 
  which 
  nutritive 
  cells 
  are 
  present 
  

   and 
  those 
  in 
  which 
  there 
  are 
  none. 
  The 
  first 
  class 
  is 
  found 
  in 
  the 
  

   Orthoptera 
  and 
  other 
  of 
  the 
  lower 
  insects, 
  the 
  second 
  is 
  found 
  in 
  

   the 
  higher 
  insects 
  and 
  may 
  be 
  subdivided 
  into 
  three 
  subgroups 
  ac- 
  

   cording 
  to 
  the 
  position 
  of 
  the 
  nutritive 
  cells. 
  The 
  first 
  subgroup 
  

  

  