﻿EXTINCTION 
  AND 
  EXTERMINATION 
  TOLMACHOFF 
  281 
  

  

  doubtful 
  distinction 
  of 
  being 
  one 
  of 
  the 
  least 
  prolific 
  of 
  animals. 
  

   It 
  is 
  also 
  suggested 
  that 
  the 
  higher 
  human 
  races 
  are 
  less 
  prolific 
  than 
  

   the 
  lower 
  ones, 
  and 
  that 
  a 
  higher 
  standard 
  of 
  living 
  is 
  usually 
  accom- 
  

   panied 
  by 
  a 
  lower 
  birth 
  rate, 
  which 
  is 
  not 
  compensated 
  by 
  a 
  corres- 
  

   pondingly 
  low 
  death 
  rate. 
  The 
  very 
  common 
  dying 
  out 
  of 
  low 
  human 
  

   races 
  that 
  bear 
  only 
  a 
  few 
  children 
  does 
  not 
  invalidate 
  this 
  statement, 
  

   because 
  this 
  phenomenon 
  is 
  due 
  to 
  certain 
  special 
  causes. 
  The 
  

   prolification 
  of 
  the 
  lower 
  animals 
  is 
  enormous. 
  According 
  to 
  Huxley's 
  

   estimate, 
  the 
  descendants 
  of 
  a 
  single 
  green 
  fly, 
  if 
  all 
  of 
  them 
  survived 
  

   and 
  multiphed, 
  would 
  at 
  the 
  end 
  of 
  one 
  summer 
  outnumber 
  the 
  

   population 
  of 
  China. 
  Common 
  house 
  flies 
  would 
  in 
  the 
  same 
  time 
  

   occupy 
  a 
  space 
  of 
  about 
  a 
  quarter 
  of 
  a 
  million 
  cubic 
  feet, 
  allowing 
  

   200,000 
  to 
  a 
  cubic 
  foot.^^ 
  These 
  examples 
  are 
  by 
  no 
  means 
  extreme. 
  

   In 
  comparison 
  with 
  them 
  we 
  find 
  an 
  example 
  no 
  less 
  striking 
  — 
  that 
  

   of 
  the 
  elephant, 
  which 
  begins 
  to 
  breed 
  at 
  the 
  age 
  of 
  thirty 
  years 
  and 
  

   has 
  a 
  period 
  of 
  gestation 
  of 
  nearly 
  two 
  years. 
  

  

  We 
  do 
  not 
  loiow 
  why 
  high 
  specialization 
  and 
  perfect 
  adaptation 
  

   to 
  certain 
  conditions 
  is 
  accompanied 
  by 
  complete 
  sterility 
  or 
  by 
  a 
  

   decrease 
  of 
  fecundity, 
  which 
  is, 
  probably, 
  the 
  first 
  stage 
  of 
  sterihty. 
  

   We 
  can 
  only 
  suggest 
  that 
  sterility 
  has 
  developed 
  slowly 
  and 
  gradually, 
  

   and 
  that 
  in 
  the 
  animal 
  kingdom 
  it 
  begins 
  with 
  unconscious 
  weakening 
  

   of 
  the 
  sexual 
  instinct. 
  Animals 
  whose 
  physical 
  and 
  psychic 
  forces 
  

   are 
  given 
  over 
  to 
  a 
  certain 
  aim, 
  such 
  as 
  the 
  achievement 
  of 
  a 
  certain 
  

   adaptation, 
  have 
  not 
  the 
  same 
  energy 
  to 
  expend 
  in 
  perpetuating 
  the 
  

   race 
  as 
  those 
  whose 
  energies 
  are 
  not 
  thus 
  expended. 
  In 
  succeeding 
  

   generations 
  this 
  transfer 
  of 
  energy 
  could 
  gradually 
  provoke 
  a 
  degrada- 
  

   tion 
  of 
  the 
  reproductive 
  organs, 
  very 
  slight 
  at 
  first, 
  by 
  dulling 
  the 
  

   sexual 
  instinct. 
  These 
  changes 
  would 
  be 
  going 
  on 
  simultaneously 
  

   with 
  the 
  final 
  and 
  fatal 
  result, 
  the 
  loss 
  of 
  the 
  power 
  of 
  reproduction. 
  

  

  DECREASE 
  OF 
  REPRODUCTION 
  IN 
  HIGHLY 
  SPECIALIZED 
  PLANTS 
  

  

  Unhappily, 
  we 
  are 
  not 
  able 
  to 
  discover 
  why 
  sterility 
  affects 
  some 
  

   individuals 
  that 
  are 
  apparently 
  in 
  perfect 
  physical 
  condition. 
  In 
  the 
  

   solution 
  of 
  this 
  problem 
  we 
  get 
  much 
  more 
  information 
  from 
  the 
  

   study 
  of 
  plants. 
  A 
  great 
  number 
  of 
  highly 
  specialized 
  cultivated 
  

   plants 
  seldom 
  or 
  never 
  produce 
  seeds 
  and 
  have 
  to 
  be 
  propagated 
  by 
  

   cuttings. 
  A 
  well-known 
  example 
  is 
  the 
  garden 
  rose. 
  Few 
  cultivated 
  

   varieties 
  of 
  the 
  banana 
  ^° 
  or 
  the 
  sugar 
  cane 
  produce 
  seed.^^ 
  The 
  

   sweet 
  potato 
  {Batatus 
  edulis) 
  has 
  been 
  preserved 
  only 
  through 
  culti- 
  

   vation.^^ 
  Through 
  cultivation, 
  also, 
  the 
  common 
  potato 
  {Solanum 
  

   tuberosum) 
  is 
  gradually 
  losing 
  its 
  power 
  to 
  produce 
  seed. 
  Bailej^ 
  

  

  2' 
  R. 
  S. 
  Lull, 
  Organic 
  evolution, 
  p. 
  104. 
  

  

  '» 
  A. 
  De 
  Candolle, 
  Origin 
  of 
  cultivated 
  plants, 
  p. 
  307. 
  

  

  31 
  Idem, 
  p. 
  156. 
  

  

  " 
  Idem, 
  p. 
  33. 
  

  

  