﻿EXTINCTION 
  AND 
  EXTERMINATION 
  TOLMACHOFF 
  283 
  

  

  a 
  gradual 
  decrease 
  in 
  prolification. 
  Such 
  specialization 
  releases 
  

   energy, 
  which 
  is 
  used 
  to 
  achieve 
  further 
  specialization 
  and 
  to 
  increase 
  

   structural 
  variability, 
  or 
  to 
  develop 
  structures 
  that 
  may 
  be 
  beyond 
  

   present 
  needs. 
  The 
  energy 
  that 
  had 
  been 
  devoted 
  to 
  reproduction 
  

   seems 
  to 
  have 
  been 
  diverted 
  to 
  the 
  multiplication 
  of 
  alterations 
  of 
  

   bodily 
  structure. 
  When 
  we 
  consider 
  the 
  spines 
  on 
  the 
  valves 
  of 
  a 
  

   Productus; 
  the 
  rich 
  ornamentation, 
  the 
  ribs, 
  spines, 
  and 
  tubercles 
  

   on 
  the 
  shells 
  of 
  ammonites; 
  the 
  peculiar 
  armor 
  and 
  forbidding 
  spines 
  

   of 
  the 
  Stegosaurus; 
  the 
  antlers 
  of 
  the 
  extinct 
  great 
  Irish 
  stag; 
  the 
  

   gigantic 
  but 
  not 
  correspondingly 
  advantageous 
  size 
  of 
  the 
  Diplodocus, 
  

   and 
  other 
  similar 
  forms, 
  we 
  can 
  only 
  conclude 
  that 
  all 
  these 
  extremely 
  

   developed 
  features 
  represent 
  an 
  unnecessary 
  excess 
  of 
  structure 
  and 
  

   waste 
  of 
  energy. 
  Extravagance 
  of 
  structure 
  decreases 
  the 
  reproduc- 
  

   tive 
  ability 
  of 
  a 
  race 
  and 
  diminishes 
  its 
  resistance 
  to 
  extermination, 
  

   although 
  at 
  the 
  same 
  time 
  the 
  race 
  may 
  appear 
  to 
  be 
  well 
  prepared 
  

   for 
  the 
  struggle 
  for 
  existence 
  — 
  a 
  fact 
  that 
  makes 
  its 
  extinction 
  inex- 
  

   plicable 
  and 
  mysterious. 
  

  

  Complete 
  sterility 
  is 
  not 
  the 
  only 
  condition 
  determining 
  the 
  extinc- 
  

   tion 
  of 
  a 
  race, 
  and 
  it 
  was 
  doubtless 
  attained 
  only 
  in 
  a 
  few 
  extinct 
  

   races, 
  but 
  partial 
  sterility, 
  or 
  the 
  decrease 
  of 
  reproductive 
  power 
  be- 
  

   yond 
  certain 
  limits, 
  is 
  probably 
  the 
  axis 
  on 
  which 
  the 
  whole 
  process 
  

   of 
  extinction 
  revolves 
  and 
  is, 
  perhaps, 
  the 
  main 
  or 
  only 
  cause 
  of 
  this 
  

   mysterious 
  phenomenon. 
  

  

  The 
  relation 
  between 
  the 
  extinction 
  of 
  a 
  race 
  and 
  its 
  fertility 
  has 
  been 
  

   very 
  little 
  considered 
  by 
  naturalists. 
  Merriam 
  suggests 
  ^* 
  that 
  dimin- 
  

   ished 
  reproduction 
  induced 
  by 
  low 
  temperature 
  would 
  be 
  a 
  barrier 
  to 
  

   the 
  geographical 
  distribution 
  of 
  a 
  certain 
  race 
  and 
  would 
  contribute 
  

   to 
  its 
  extinction 
  ; 
  but 
  if 
  the 
  race 
  had 
  preserved 
  its 
  structural 
  flexibility 
  — 
  

   in 
  other 
  words, 
  if 
  it 
  had 
  not 
  been 
  overspecialized 
  and 
  its 
  productive 
  

   ability 
  were 
  normal 
  — 
  it 
  would 
  gradually 
  become 
  adapted 
  to 
  new 
  

   conditions 
  and 
  survive 
  them. 
  

  

  HIGH 
  SPECIALIZATION 
  AND 
  INCREASED 
  FERTILITY 
  OF 
  PARASITES 
  

  

  We 
  know 
  of 
  only 
  one 
  class 
  of 
  animals, 
  the 
  parasites, 
  in 
  which 
  close 
  

   adaptation 
  to 
  the 
  immediate 
  environment, 
  causing 
  an 
  unavoidably 
  

   great 
  overspeciaHzation, 
  has 
  been 
  accompanied 
  by 
  increased 
  fertility. 
  

   However, 
  this 
  apparent 
  exception 
  only 
  supports 
  the 
  view 
  here 
  ad- 
  

   vanced. 
  In 
  parasites 
  the 
  specialization 
  is 
  degenerative. 
  They 
  lose 
  

   the 
  organs 
  of 
  locomotion, 
  and 
  the 
  special 
  senses 
  and 
  the 
  nervous 
  

   system 
  accordingly 
  degenerates. 
  The 
  external 
  skeleton 
  becomes 
  

   simpler 
  or 
  is 
  entirely 
  lost. 
  Reduction 
  of 
  the 
  vegetative 
  organs, 
  such 
  

   as 
  those 
  of 
  respiration 
  and 
  circulation, 
  of 
  the 
  alimentary 
  canal, 
  and 
  

   of 
  the 
  digestive 
  glands 
  is 
  common. 
  ^^ 
  These 
  organs 
  therefore 
  be- 
  

  

  3* 
  H. 
  F. 
  Osbom, 
  The 
  age 
  of 
  mammals, 
  p. 
  504. 
  

   3» 
  R. 
  S. 
  Lull, 
  Organic 
  evolution, 
  p. 
  266. 
  

  

  