﻿1875.] 
  Sea-bottom 
  procured 
  by 
  H.M.S. 
  ' 
  Challenger.' 
  243 
  

  

  occupied 
  by 
  mineral 
  deposit, 
  which, 
  when 
  the 
  shell 
  has 
  been 
  dissolved 
  

   away 
  by 
  dilute 
  acid, 
  presents 
  a 
  perfect 
  internal 
  cast 
  of 
  'its 
  cavities. 
  By 
  

   the 
  application 
  of 
  this 
  method 
  to 
  Mr. 
  Beete 
  Jukes's 
  Australian 
  dredgings, 
  

   my 
  coadjutors, 
  Messrs. 
  W. 
  K. 
  Parker 
  and 
  T. 
  Eupert 
  Jones, 
  obtained 
  a 
  

   series 
  of 
  internal 
  casts 
  of 
  most 
  wonderful 
  beauty 
  and 
  completeness, 
  on 
  

   which 
  I 
  have 
  based 
  my 
  interpretation 
  of 
  the 
  organic 
  structure 
  of 
  Eozoon 
  

   Canaclense. 
  Having 
  myself 
  examined 
  in 
  the 
  same 
  manner 
  a 
  portion 
  of 
  

   the 
  Foraminiferal 
  sand 
  dredged 
  by 
  Capt. 
  Spratt 
  in 
  the 
  JEgean 
  (kindly 
  

   placed 
  in 
  my 
  hands 
  by 
  Mr. 
  J. 
  G-wyn 
  Jeffreys), 
  I 
  have 
  found 
  that 
  it 
  

   yielded 
  a 
  great 
  variety 
  of 
  these 
  beautiful 
  models, 
  not 
  only 
  of 
  the 
  bodies 
  

   of 
  Poraminifera, 
  but 
  also 
  of 
  the 
  sarcodic 
  network 
  which 
  interpenetrates 
  

   the 
  calcareous 
  network 
  of 
  the 
  shell 
  and 
  spines 
  of 
  Echinida*. 
  

  

  Alike 
  in 
  Mr. 
  Jukes's 
  and 
  in 
  Capt. 
  Spratt's 
  dredgings, 
  some 
  of 
  these 
  

   casts 
  are 
  in 
  green 
  silicates 
  and 
  some 
  in 
  ochreous, 
  corresponding 
  precisely 
  

   to 
  the 
  two 
  kinds 
  of 
  fossil 
  casts 
  described 
  by 
  Prof. 
  Ehrenberg. 
  The 
  

   difference 
  I 
  presume 
  to 
  depend 
  upon 
  the 
  degree 
  of 
  oxidation 
  of 
  the 
  iron; 
  

   but 
  as 
  these 
  casts 
  are 
  far 
  too 
  precious 
  to 
  be 
  sacrificed 
  for 
  chemical 
  ana- 
  

   lysis, 
  I 
  cannot 
  speak 
  with 
  certainty 
  on 
  this 
  point. 
  

  

  As 
  it 
  is 
  only 
  in 
  certain 
  limited 
  areas 
  of 
  the 
  sea-bottom 
  that 
  this 
  replace- 
  

   ment 
  of 
  the 
  sarcodic 
  bodies 
  of 
  Foraminifera 
  by 
  mineral 
  deposit 
  is 
  met 
  

   with, 
  it 
  has 
  always 
  seemed 
  to 
  me 
  next 
  to 
  certain 
  that 
  there 
  must 
  be 
  some 
  

   peculiarity 
  in 
  the 
  composition 
  of 
  the 
  sea-water 
  of 
  those 
  areas 
  (produced, 
  

   perhaps, 
  by 
  the 
  outburst 
  of 
  submarine 
  springs 
  highly 
  charged 
  with 
  ferru- 
  

   ginous 
  silicates) 
  which 
  gives 
  to 
  them 
  a 
  capability 
  that 
  does 
  not 
  exert 
  

   itself 
  elsewhere 
  ; 
  and 
  this 
  now 
  seems 
  yet 
  more 
  probable 
  from 
  the 
  circum- 
  

   stance 
  that, 
  notwithstanding 
  the 
  vast 
  extent 
  over 
  which 
  the 
  ' 
  Challenger 
  ' 
  

   soundings 
  and 
  dredgings 
  have 
  been 
  prosecuted, 
  only 
  two 
  or 
  three 
  cases 
  

   of 
  the 
  kind 
  have 
  been 
  noted 
  — 
  those, 
  namely, 
  of 
  the 
  " 
  greenish 
  sands 
  " 
  

   brought 
  up 
  from 
  98 
  and 
  150 
  fathoms 
  in 
  the 
  region 
  of 
  the 
  Agulhas 
  

   Current 
  and 
  in 
  one 
  or 
  two 
  other 
  localities. 
  It 
  is 
  a 
  fact 
  of 
  peculiar 
  in- 
  

   terest, 
  moreover, 
  that 
  the 
  calcareous 
  shells 
  should 
  have 
  here 
  disappeared, 
  

   just 
  as 
  they 
  have 
  done 
  in 
  ordinary 
  green 
  sand 
  ; 
  and 
  this, 
  too, 
  although 
  

   the 
  depth 
  was 
  so 
  small 
  as 
  altogether 
  to 
  forbid 
  the 
  idea 
  that 
  their 
  dis- 
  

   appearance 
  is 
  due 
  to 
  any 
  solvent 
  process 
  brought 
  about 
  by 
  the 
  agencies 
  

   to 
  which 
  Prof. 
  Wyville 
  Thomson 
  attributes 
  the 
  removal 
  of 
  the 
  calcareous 
  

   deposit 
  generated 
  by 
  Grlobigerine 
  life. 
  

  

  £s 
  ow 
  in 
  the 
  residue 
  left 
  after 
  the 
  decalcification 
  of 
  Capt. 
  Spratt's 
  dredg- 
  

   ings, 
  I 
  noticed 
  a 
  number 
  of 
  small 
  particles 
  of 
  red 
  clay, 
  some 
  of 
  them 
  pre- 
  

   senting 
  no 
  definite 
  shape, 
  whilst 
  others 
  approximated 
  sufficiently 
  closely 
  

   inform 
  and 
  size 
  to 
  the 
  green 
  and 
  ochreous 
  " 
  internal 
  casts" 
  to 
  induce 
  me 
  

   to 
  surmise 
  that 
  these 
  also 
  had 
  been 
  originally 
  deposited 
  in 
  the 
  chambers 
  

   of 
  Porarninifera 
  — 
  their 
  material 
  being 
  probably 
  very 
  nearly 
  the 
  same, 
  

  

  * 
  Of 
  these 
  I 
  hope 
  to 
  be 
  able, 
  ere 
  long, 
  to 
  give 
  a 
  detailed 
  account, 
  in 
  illustration 
  of 
  

   the 
  similar 
  models 
  of 
  the 
  animal 
  of 
  Eozoon 
  obtained 
  by 
  the 
  decalcification 
  of 
  its 
  ser- 
  

   pentine 
  lamellas. 
  

  

  