﻿36 
  

  

  Prof. 
  C. 
  W. 
  Thomson 
  on 
  the 
  

  

  [Nov. 
  26, 
  

  

  This 
  origin 
  of 
  the 
  spines 
  from 
  the 
  papillae 
  can 
  be 
  well 
  seen 
  with 
  a 
  

   moderate 
  power 
  on 
  the 
  periphery 
  of 
  the 
  sphere. 
  The 
  spines 
  are 
  

   hollow 
  and 
  flexible; 
  they 
  naturally 
  radiate 
  regularly 
  from 
  the 
  direc- 
  

   tion 
  of 
  the 
  centre 
  of 
  the 
  sphere 
  ; 
  but 
  in 
  specimens 
  which 
  have 
  been 
  

   placed 
  under 
  the 
  microscope 
  with 
  the 
  greatest 
  care, 
  they 
  are 
  usually 
  

   entangled 
  together 
  in 
  twisted 
  bundles. 
  They 
  are 
  so 
  fragile 
  that 
  the 
  

   weight 
  of 
  the 
  shell 
  itself, 
  rolling 
  about 
  with 
  the 
  motion 
  of 
  the 
  ship, 
  is 
  

   usually 
  sufficient 
  to 
  break 
  off 
  the 
  whole 
  of 
  the 
  spines 
  and 
  leave 
  only 
  

   the 
  papillae 
  projecting 
  from 
  its 
  surface, 
  in 
  the 
  course 
  of 
  a 
  few 
  minutes. 
  

   In 
  some 
  examples, 
  either 
  those 
  in 
  process 
  of 
  development, 
  or 
  a 
  series 
  

   showing 
  a 
  varietal 
  divergence 
  from 
  the 
  ordinary 
  type, 
  the 
  shell 
  is 
  very 
  

   thin 
  and 
  almost 
  perfectly 
  smooth, 
  with 
  neither 
  papillae 
  nor 
  spines, 
  nor 
  

   any 
  visible 
  structure, 
  except 
  the 
  two 
  classes 
  of 
  pores, 
  which 
  are 
  constant. 
  

  

  The 
  chamber 
  of 
  Orbulina 
  is 
  often 
  almost 
  empty 
  ; 
  even 
  in 
  the 
  case 
  of 
  

   examples 
  from 
  the 
  surface, 
  which 
  appear, 
  from 
  the 
  freshness 
  and 
  trans- 
  

   parency 
  of 
  the 
  shell, 
  to 
  be 
  living, 
  it 
  is 
  never 
  full 
  of 
  sarcode 
  ; 
  but 
  it 
  fre- 
  

   quently 
  contains 
  a 
  small 
  quantity 
  of 
  yellow 
  sarcode 
  stuck 
  against 
  one 
  

   side, 
  as 
  in 
  the 
  last 
  chamber 
  of 
  Globigerina. 
  Sometimes, 
  but 
  by 
  no 
  means 
  

   constantly, 
  within 
  the 
  chamber 
  of 
  Orbulina 
  there 
  is 
  a 
  little 
  chain 
  of 
  three 
  

   or 
  four 
  small 
  chambers 
  singularly 
  resembling 
  in 
  form, 
  in 
  proportion, 
  and 
  

   in 
  sculpture 
  a 
  small 
  Globigerina 
  ; 
  and 
  sometimes, 
  but 
  again 
  by 
  no 
  means 
  

   constantly, 
  spines 
  are 
  developed 
  on 
  the 
  surface 
  of 
  the 
  calcareous 
  walls 
  of 
  

   these 
  inner 
  chambers, 
  like 
  those 
  on 
  the 
  test 
  of 
  Globigerina. 
  The 
  spines 
  

   radiate 
  from 
  the 
  position 
  of 
  the 
  centre 
  of 
  the 
  chambers 
  and 
  abut 
  against 
  

   the 
  insides 
  of 
  the 
  wall 
  of 
  the 
  Orbulina 
  (PI. 
  IT.). 
  In 
  a 
  few 
  cases, 
  the 
  inner 
  

   chambers 
  have 
  been 
  observed, 
  apparently 
  arising 
  within 
  or 
  amidst 
  the 
  

   sarcode 
  adhering 
  to 
  the 
  wall 
  of 
  the 
  Orbulina. 
  

  

  Major 
  Owen 
  regards 
  Orbulina 
  as 
  a 
  distinct 
  organism, 
  nearly 
  allied 
  to 
  

   Globigerina, 
  but 
  differing 
  so 
  far 
  from 
  it 
  as 
  to 
  justify 
  its 
  separation 
  into 
  a 
  

   special 
  subgenus. 
  He 
  considers 
  the 
  small 
  inner 
  chamber 
  of 
  Orbulina 
  to 
  

   represent 
  the 
  smaller 
  chamber 
  of 
  Globigerina, 
  and 
  the 
  outer 
  wall 
  as 
  

   the 
  equivalent 
  of 
  the 
  large 
  outer 
  chamber 
  of 
  Globigerina, 
  developed 
  in 
  this 
  

   form 
  as 
  an 
  investing 
  chamber. 
  Count 
  Pourtales, 
  Max-Schultze, 
  and 
  

   Krohn, 
  on 
  the 
  other 
  hand, 
  believe, 
  on 
  account 
  of 
  the 
  close 
  resemblance 
  in 
  

   structure 
  between 
  the 
  two 
  shells, 
  their 
  constant 
  association, 
  and 
  the 
  un- 
  

   doubted 
  fact 
  that 
  an 
  object 
  closely 
  resembling 
  a 
  young 
  Globigerina 
  is 
  

   often 
  found 
  within 
  Orbulina, 
  that 
  the 
  latter 
  is 
  simply 
  a 
  special 
  reproduc- 
  

   tive 
  chamber 
  budded 
  from 
  the 
  former, 
  and 
  capable 
  of 
  existing 
  indepen- 
  

   dently. 
  I 
  am 
  rather 
  inclined 
  to 
  the 
  latter 
  view, 
  although 
  I 
  think 
  much 
  

   careful 
  observation 
  is 
  still 
  required 
  to 
  substantiate 
  it 
  ; 
  and 
  some, 
  even 
  of 
  

   our 
  own, 
  observations 
  would 
  seem 
  to 
  tell 
  somewhat 
  in 
  the 
  opposite 
  direc- 
  

   tion. 
  Although 
  Orbulina 
  and 
  Globigerina 
  are 
  very 
  usually 
  associated, 
  

   they 
  are 
  so 
  in 
  different 
  proportions 
  in 
  different 
  localities 
  ; 
  and 
  in 
  the 
  icy 
  

   sea 
  to 
  the 
  south 
  of 
  Kerguelen, 
  although 
  Globigerina 
  was 
  constantly 
  

   taken 
  in 
  the 
  surface-net, 
  not 
  a 
  single 
  Orbulina 
  was 
  detected. 
  Like 
  

  

  