﻿1875.] 
  Sea-bottom 
  procured 
  by 
  H.M.S. 
  ' 
  Challenger? 
  237 
  

  

  sheet 
  of 
  my 
  ■ 
  Introduction 
  to 
  the 
  Study 
  of 
  the 
  Eoraniinifera 
  ' 
  comprising 
  

   the 
  Grlobigerine 
  family 
  passed 
  through 
  the 
  press, 
  but 
  which 
  I 
  have 
  my- 
  

   self 
  subsequently 
  confirmed 
  in 
  every 
  particular) 
  it 
  seems 
  an 
  almost 
  inevit- 
  

   able 
  inference 
  that 
  the 
  subsidence 
  of 
  the 
  Globigerince 
  to 
  the 
  bottom 
  is 
  the 
  

   consequence, 
  not 
  of 
  their 
  death, 
  but 
  of 
  the 
  increasing 
  thickness 
  and 
  

   weight 
  of 
  their 
  shells, 
  produced 
  by 
  living 
  action. 
  As 
  long 
  as 
  the 
  number 
  

   of 
  segments 
  continues 
  to 
  increase, 
  the 
  carbonate 
  of 
  lime 
  separated 
  by 
  the 
  

   sarcodic 
  body 
  from 
  the 
  circumambient 
  water 
  goes 
  to 
  form 
  the 
  walls 
  of 
  

   additional 
  chambers 
  ; 
  but 
  when 
  this 
  chamber-formation 
  ceases 
  (which 
  

   usually 
  occurs 
  when 
  the 
  shell 
  consists 
  of 
  either 
  12 
  or 
  16 
  segments), 
  it 
  

   is 
  applied 
  to 
  thicken 
  the 
  walls 
  of 
  the 
  chambers 
  already 
  formed 
  ; 
  and 
  

   from 
  the 
  rapid 
  subsidence 
  of 
  the 
  Globigerince 
  taken 
  up 
  from 
  the 
  sea- 
  

   bottom 
  when 
  thrown 
  into 
  a 
  jar 
  of 
  sea-water, 
  it 
  seems 
  to 
  me 
  inconceiv- 
  

   able 
  that 
  they 
  can 
  be 
  floated 
  by 
  their 
  animal 
  inhabitants 
  when 
  once 
  the 
  

   exogenous 
  deposit 
  has 
  attained 
  any 
  considerable 
  thickness. 
  

  

  That 
  the 
  Globigerince 
  which 
  have 
  subsided 
  to 
  the 
  bottom 
  continue 
  to 
  

   live 
  there, 
  is 
  further 
  indicated 
  by 
  the 
  condition 
  of 
  the 
  sarcodic 
  contents 
  

   of 
  their 
  shells. 
  In 
  any 
  sample 
  of 
  Globigerina-ooze 
  that 
  I 
  have 
  seen 
  

   brought 
  up 
  by 
  the 
  dredge 
  or 
  the 
  sounding-apparatus, 
  part 
  of 
  the 
  shells 
  

   (presumably 
  those 
  of 
  the 
  surface-layer) 
  were 
  filled 
  with 
  a 
  sarcode 
  body 
  

   corresponding 
  in 
  condition 
  with 
  that 
  of 
  Eoraminifera 
  known 
  to 
  live 
  on 
  

   the 
  sea-bed, 
  and 
  retaining 
  the 
  characteristic 
  form 
  of 
  the 
  organism 
  after 
  

   the 
  removal 
  of 
  the 
  shell 
  by 
  dilute 
  acid. 
  As 
  Dr. 
  Wallich 
  pointed 
  out 
  

   (' 
  North- 
  Atlantic 
  Sea-bed,' 
  p. 
  139), 
  the 
  sarcode 
  of 
  these 
  is 
  viscid, 
  and 
  

   inclined 
  to 
  coalesce 
  again 
  when 
  crushed 
  ; 
  the 
  shell 
  has 
  a 
  vivid 
  but 
  light 
  

   burnt-sienna 
  colour, 
  and 
  sarcodic 
  bosses, 
  like 
  retracted 
  pseudopodia, 
  are 
  

   distinguishable 
  upon 
  its 
  exterior. 
  The 
  only 
  misgiving 
  I 
  ever 
  had 
  in 
  regard 
  

   to 
  the 
  living 
  condition 
  of 
  the 
  Globigerince 
  presenting 
  these 
  characters, 
  

   was 
  caused 
  by 
  the 
  absence 
  of 
  any 
  pseudopodia] 
  extensions; 
  and 
  this 
  

   source 
  of 
  doubt 
  has 
  been 
  now 
  removed 
  by 
  the 
  statement 
  of 
  Prof. 
  

   Wyville 
  Thomson, 
  that 
  no 
  pseudopodia 
  have 
  ever 
  been 
  observed 
  by 
  Mr. 
  

   Murray 
  to 
  be 
  put 
  forth 
  by 
  the 
  Globigerince 
  captured 
  in 
  surface-waters. 
  — 
  

   In 
  the 
  same 
  sample 
  will 
  be 
  found 
  shells 
  distinguishable 
  from 
  the 
  pre- 
  

   ceding 
  by 
  their 
  dingy 
  look 
  and 
  greyish 
  colour, 
  by 
  the 
  want 
  of 
  consistence 
  

   and 
  viscidity 
  in 
  their 
  sarcode 
  contents, 
  and 
  by 
  the 
  absence 
  of 
  any 
  external 
  

   sarcodic 
  investment 
  ; 
  these 
  are 
  presumably 
  dead. 
  Other 
  shells, 
  again, 
  

   are 
  entirely 
  empty 
  ; 
  and 
  even 
  when 
  the 
  surface-stratum 
  is 
  formed 
  of 
  

   perfect 
  Globigerince, 
  the 
  character 
  of 
  the 
  deposit 
  soon 
  changes 
  as 
  it 
  is 
  

   traced 
  downwards. 
  " 
  The 
  sediment," 
  as 
  was 
  correctly 
  stated 
  by 
  Prof. 
  

   Wyville 
  Thomson, 
  " 
  gradually 
  becomes 
  more 
  compact 
  ; 
  and 
  a 
  slight 
  grey 
  

   colour 
  (due, 
  probably, 
  to 
  the 
  decomposing 
  organic 
  matter) 
  becomes 
  more 
  

   pronounced, 
  while 
  perfect 
  shells 
  of 
  Globigerina 
  almost 
  disappear, 
  frag- 
  

   ments 
  become 
  smaller, 
  and 
  calcareous 
  mud, 
  structureless 
  and 
  in 
  a 
  fine 
  

   state 
  of 
  division, 
  is 
  in 
  greatly 
  preponderating 
  proportion" 
  ('Depths 
  of 
  

   the 
  Sea,' 
  p. 
  410). 
  These 
  facts 
  seem 
  to 
  me 
  to 
  mark 
  very 
  strongly 
  the 
  

  

  