﻿AGE 
  OF 
  THE 
  EARTH 
  — 
  CHAMBERLIN 
  AND 
  OTHERS. 
  267 
  

  

  reproductive 
  output 
  that 
  they 
  may 
  have 
  previously 
  initiated," 
  such 
  

   as 
  oogamy 
  and 
  fertilization 
  in 
  situ. 
  

  

  The 
  picture 
  presented 
  by 
  this 
  line 
  of 
  carefully 
  founded 
  reasoning 
  

   is 
  even 
  more 
  impressive 
  in 
  its 
  demands 
  upon 
  time 
  than 
  the 
  argument 
  

   we 
  have 
  presented 
  from 
  animal 
  life. 
  It 
  is 
  summed 
  up 
  thus 
  : 
  Plants 
  

   of 
  complex 
  organization 
  and 
  function 
  — 
  deductively 
  of 
  higher 
  organ- 
  

   ization 
  than 
  can 
  be 
  to-day 
  found 
  among 
  the 
  algee 
  — 
  had 
  worked 
  out 
  

   their 
  attainments 
  before 
  their 
  arrival 
  on 
  the 
  land, 
  and 
  probably 
  this 
  

   organic 
  achievement, 
  not 
  surpassed 
  in 
  the 
  seas 
  of 
  to-day, 
  was 
  accom- 
  

   plished 
  at 
  a 
  stage 
  in 
  earth 
  history 
  long 
  before 
  the 
  Cambrian 
  epoch 
  

   brought 
  with 
  it 
  the 
  tangible 
  evidence 
  of 
  the 
  complex 
  animals. 
  The 
  

   argument 
  from 
  the 
  plants 
  is 
  more 
  highly 
  deductive 
  than 
  that 
  from 
  

   animals, 
  but 
  its 
  steps 
  are 
  logically 
  taken 
  from 
  effect 
  to 
  cause, 
  and 
  in 
  

   its 
  presence 
  we 
  must 
  stand 
  uncovered 
  at 
  the 
  inconceivable 
  lapses 
  of 
  

   earth 
  time 
  through 
  which 
  these 
  transmigrant 
  plants 
  were 
  slowly 
  

   working 
  out 
  their 
  organization 
  in 
  the 
  waters 
  when 
  there 
  was 
  no 
  

   permanent 
  land 
  — 
  a 
  period 
  of 
  time 
  which 
  must 
  have 
  been 
  longer 
  than 
  

   all 
  time 
  that 
  has 
  passed 
  since 
  the 
  emergence 
  of 
  the 
  Laurentian 
  or 
  the 
  

   basal 
  rock 
  complex 
  of 
  the 
  great 
  shields 
  of 
  the 
  earth. 
  

  

  II. 
  

  

  If 
  we 
  are 
  prepared 
  to 
  concede 
  the 
  steadily 
  increasing 
  weight 
  of 
  

   evidence 
  of 
  the 
  polyphyletic 
  origin 
  of 
  genera 
  which 
  recent 
  researches 
  

   have 
  indicated 
  for 
  so 
  many 
  different 
  groups 
  of 
  life, 
  and 
  can 
  compel 
  

   our 
  conception 
  to 
  grasp 
  the 
  duration 
  of 
  the 
  vast 
  unrecorded 
  past 
  of 
  

   life 
  history, 
  there 
  remains 
  another 
  phase 
  of 
  the 
  paleontological 
  rec- 
  

   ord 
  which 
  in 
  part 
  emphasizes 
  and 
  in 
  part 
  serves 
  as 
  a 
  check 
  on 
  this* 
  

   conception. 
  It 
  has 
  fallen 
  to 
  me 
  to 
  study 
  the 
  earliest 
  recorded 
  ex- 
  

   pressions 
  of 
  dependent 
  life 
  — 
  that 
  is, 
  the 
  beginnings, 
  so 
  far 
  as 
  we 
  can 
  

   find 
  them, 
  of 
  such 
  consociations 
  of 
  animals 
  as 
  we 
  are 
  wont 
  to 
  desig- 
  

   nate 
  as 
  parasitic, 
  mutualistic, 
  and 
  symbiotic, 
  wherein 
  one 
  creation 
  

   has 
  depended 
  upon 
  or 
  adjusted 
  itself 
  to 
  the 
  life 
  functions 
  or 
  habits 
  

   of 
  another, 
  or 
  has 
  sought 
  mechanical 
  protection 
  at 
  the 
  cost 
  of 
  its 
  

   own 
  locomotive 
  independence. 
  Two 
  very 
  obvious 
  facts 
  seem 
  to 
  

   stand 
  out 
  as 
  a 
  result 
  of 
  these 
  inquiries: 
  (1) 
  That 
  these 
  interdepend- 
  

   ent 
  conditions 
  with 
  which 
  the 
  living 
  world 
  is 
  rife 
  to-day, 
  in 
  passing 
  

   backward 
  to 
  the 
  early 
  stages 
  of 
  Paleozoic 
  time, 
  become 
  palpably 
  

   fewer 
  ; 
  indeed, 
  while 
  such 
  conditions 
  are 
  well 
  marked 
  in 
  some 
  groups 
  

   and 
  common 
  in 
  others 
  during 
  the 
  middle 
  and 
  later 
  Paleozoic, 
  they 
  

   are 
  very 
  unusual 
  in 
  the 
  earlier 
  stages 
  and 
  in 
  the 
  Cambrian 
  fauna 
  are 
  

   little 
  more 
  than 
  suggested. 
  (2) 
  This 
  dependent 
  state 
  seems 
  with 
  

   reasonable 
  clarity 
  to 
  be 
  resolvable 
  into 
  an 
  original 
  loss 
  of 
  loco- 
  

   motive 
  independence, 
  a 
  willingness 
  to 
  be 
  fed 
  rather 
  than 
  to 
  feed, 
  an 
  

   adaptation 
  to 
  an 
  easier 
  mode 
  of 
  life. 
  The 
  commanding 
  percentage 
  

  

  