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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  of 
  these 
  reversionary 
  movements 
  among 
  the 
  Amphibia 
  and 
  the 
  

   Mollusca 
  and 
  many 
  Mammalia, 
  and 
  it 
  seems 
  highly 
  probable 
  that 
  a 
  

   more 
  exact 
  knowledge 
  of 
  extinct 
  life 
  will 
  establish 
  these 
  suggestions 
  

   and 
  awaken 
  others. 
  

  

  The 
  Plankton 
  epoch, 
  says 
  Church, 
  gave 
  rise 
  to 
  the 
  first 
  encysted 
  

   flagellate 
  plants 
  which, 
  under 
  conditions 
  of 
  the 
  Benthon, 
  developed 
  

   multicellular 
  thallus, 
  tissues 
  and 
  organs 
  of 
  special 
  function 
  and 
  a 
  

   reproductive 
  mechanism 
  contrived 
  so 
  as 
  to 
  minimize 
  waste. 
  Then 
  

   followed 
  the 
  epoch 
  of 
  the 
  land 
  flora 
  brought 
  on 
  by 
  the 
  transmigra- 
  

   tion 
  of 
  highly 
  developed 
  algae 
  which 
  in 
  fact 
  " 
  appear 
  to 
  have 
  been 
  

   more 
  highly 
  organized 
  than 
  any 
  single 
  algal 
  type 
  at 
  present 
  known 
  

   to 
  exist 
  in 
  the 
  sea." 
  " 
  The 
  algae 
  of 
  transmigration 
  may 
  be 
  * 
  * 
  * 
  

   said 
  to 
  have 
  combined 
  the 
  best 
  features 
  of 
  the 
  known 
  great 
  con- 
  

   ventional 
  series 
  of 
  marine 
  phytobenthon." 
  " 
  The 
  origins 
  of 
  all 
  the 
  

   main 
  successful 
  adaptations 
  of 
  the 
  land 
  are 
  to 
  be 
  traced 
  down 
  to 
  

   the 
  benthic 
  phase 
  of 
  the 
  sea." 
  In 
  this 
  impressive 
  statement 
  we 
  are 
  

   confronted 
  by 
  the 
  quality 
  of 
  the 
  plant 
  life 
  at 
  its 
  emergence 
  from 
  the 
  

   sea. 
  

  

  Now 
  as 
  to 
  the 
  period 
  of 
  its 
  emergence, 
  of 
  foremost 
  importance 
  

   to 
  our 
  present 
  consideration, 
  Thomas 
  C. 
  Chamberlin 
  in 
  1913 
  directed 
  

   attention 
  to 
  the 
  fact 
  that 
  the 
  pre-Cambrian 
  rock 
  complex 
  is 
  divided 
  

   into 
  earlier 
  and 
  later 
  stages 
  on 
  the 
  basis 
  of 
  the 
  degree 
  of 
  disintegra- 
  

   tion 
  of 
  the 
  exposed 
  rock 
  surface. 
  In 
  the 
  lower 
  division 
  there 
  is 
  an 
  

   immature 
  disintegration 
  which 
  implies 
  partial 
  decomposition, 
  but 
  

   the 
  mature 
  disintegration 
  of 
  the 
  later 
  division 
  implies, 
  he 
  says, 
  " 
  some 
  

   restraining 
  agency 
  that 
  held 
  the 
  rock 
  in 
  place 
  while 
  the 
  slow 
  weather- 
  

   ing 
  completed 
  its 
  work." 
  " 
  This 
  view 
  favors 
  the 
  existence 
  of 
  a 
  

   vegetal 
  covering 
  of 
  the 
  land 
  as 
  far 
  back 
  as 
  this 
  period." 
  

  

  Church, 
  therefore, 
  has 
  a 
  well-found 
  argument 
  when 
  in 
  the 
  pres- 
  

   ence 
  of 
  this 
  fact 
  of 
  pre-Cambrian 
  weathering 
  he 
  intimates 
  that 
  it 
  was 
  

   with 
  the 
  uplifting 
  and 
  exposure 
  of 
  the 
  primary 
  rock 
  to 
  the 
  air 
  that 
  

   " 
  the 
  marine 
  organism 
  was 
  brought 
  into 
  direct 
  association 
  with 
  atmos- 
  

   pheric 
  air 
  and 
  subaerial 
  environment 
  to 
  mark 
  out 
  new 
  lines 
  of 
  pro- 
  

   gression 
  to 
  still 
  higher 
  and 
  more 
  strenuous 
  forms 
  of 
  land 
  life, 
  though 
  

   these 
  are 
  again 
  necessarily 
  expressed 
  in 
  terms 
  of 
  preceding 
  organiza- 
  

   tion 
  and 
  mechanism." 
  The 
  point 
  to 
  be 
  made 
  here 
  is 
  that 
  with 
  the 
  

   earliest 
  lifting 
  of 
  land 
  from 
  the 
  sea, 
  benthic 
  algae 
  of 
  advanced 
  struc- 
  

   ture, 
  " 
  the 
  remarkable 
  algae 
  of 
  transmigration," 
  as 
  he 
  has 
  character- 
  

   ized 
  them, 
  got 
  their 
  foothold 
  on 
  the 
  land. 
  " 
  The 
  evolution 
  of 
  the 
  

   land 
  flora 
  was 
  a 
  phase 
  of 
  transmigration 
  in 
  situ'''' 
  and 
  did 
  not 
  in- 
  

   volve 
  a 
  preliminary 
  landward 
  migration 
  by 
  the 
  way 
  of 
  fresh 
  water, 
  

   •' 
  tjie 
  biological 
  factors 
  being 
  exposure 
  to 
  more 
  or 
  less 
  desiccation 
  and 
  

   the 
  removal 
  of 
  the 
  food 
  solution." 
  " 
  The 
  few 
  races 
  that 
  survived 
  

   only 
  did 
  so 
  by 
  pressing 
  to 
  the 
  utmost 
  any 
  principles 
  of 
  economy 
  in 
  

  

  