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EX  LIBRIS. 

Bertram   C+   3L   TOtntrle, 


DUBLIN  REVIEW.  S.R.B.— 71 

FATHER  WASMANN,  SJ.,  has  long  been  known 
to  men  of  science  as  the  foremost  living  authority 
on  ants  and  termites  and  their  inquitines,  and  his  special 
books  on  science  in  its  relation  to  religion  have  been 
noticed  in  this  Review  as  they  appeared  both  in  their 
German  and  their  English  dress.  He  has  not  merely 
contributed  of  his  own  work  to  science  but  has  achieved 
the  even  greater  end  of  forming  a  school  of  scientific 
observers  and  writers  amongst  German  members  of  his 
society.  Fr  Assmuth,  now  we  believe  in  India,  is  well 
known  for  his  observations  in  the  same  field  of  knowledge 
as  that  of  his  teacher,  and  now  we  have  from  the  pen  of 
Fr  Karl  Frank,  S.J.,  a  most  interesting  work  ( The  Theory 
of  Evolution  in  the  Light  of  Facts.  Trans,  by  Charles  T. 
Druery.  London:  Kegan  Paul.  1913.  Price  53.  net) 
containing  a  chapter  by  Fr  Wasmann  on  the  subject 
which  has  formed  the  work  of  his  life. 

The  various  theories  which  have  been  put  forward  by 
Lamarck,  by  Darwin  and  by  the  "  neo  "  followers  of 
either  of  these  authorities  are  very  fully  considered  by 
Fr  Frank,  who  points  out  the  many  difficulties  which 
arise  when  one  tries  to  square  the  results  of  observation 
with  any  of  the  explanations  at  present  before  the 
scientific  world. 

One  of  the  most  interesting  sections  of  the  work  is  that 
which  deals  with  the  common  origin  of  plants  and 
animals.  Nearly  all  modern  theories  of  evolution  assume 
a  common  low  form  of  life  from  which  branched  off  in 
the  one  direction  protozoa  and  in  the  other  protophyta, 
the  simplest  forms  of  animal  and  of  vegetable  life.  Fr 
Frank  entirely  differs  from  this  view,  and,  as  the  result 
of  a  philosophical  argument  of  great  cogency  and  interest, 
concludes  that  "  animals  and  plants  cannot  be  brought 
into  genetic  connexion,"  and  this  because,  the  entire 
"  idea  "  of  the  two  being  wholly  different,  it  would  be 
impossible  for  the  one  to  become  the  other  without  a 
total  alteration  of  its  own  being. 

Fr  Frank  in  this  and  in  other  points  embraces  the 
polyphyletic  view  of  evolurion,  which  h;.  s  been  set  forward 
as  an  explanation  by  more  than  one  wri ,  er,  an  explanation 

•which,  whilst  believing  in  transform  Ism  within  great 
groups,  does  not  think  that  it  can  be  shown  to  account 
for  the  groups  themselves.  The  book  is  one  which  will 
interest  all  philosophical  biologists.  B.  C.  A.  W. 


MR.  C.  T.  DRUERY'S  translation 
of  Father  Karl  Frank's  work  on 
The  Theory  of  Evolution  in  the 
Light  of  Facts  *  is  rendered  un- 
necessarily difficult  of  reading  for 
ordinary  persons  by  a  rather  too 
close  adherence  to  the  idiom  of 
the  original— as,  for  example,  in 
the  use  of  "  also  "  where  not  re- 
quired by  English  construction. 
There  are  also  misleading  trans- 
lations which  should  be  corrected 
in  a  second  edition,  such  as  " inter- 
uterine  "  where  "  intra-uterine  " 
is  intended  (p.  29  note)  and 
"physician"  for  u  physicist  "  (p. 
83  note).  After  these  slight 
criticisms  we  hasten  to  say  that 
the  work  itself  is  interesting  and 
useful,  and  worthy  of  careful  study 

by    all    interested    in    biological 

problems.     Its  author  deals,  inter 

alia,  with  the  question  of  vitalism 

which  has  recently  been  so  much 

before  the  public,  and  shows,  as 

others  have  done  before  him,  that 

!  the  chemical  explanation   of  life 

I  is  in  no  sense  a  complete  expla- 

I  nation : 

"  Is  a  chemical  formula  imaginable 
which  can  express  'inheritance'  ?  What 
formula  has  conscience,  and  what  struc- 
ture and  organization  can  present  it 
graphically  ?  All  that,  however,  belongs 
to  'life'  and  should  be  explained" 
(p.  101). 

He  further  considers  the  theories 
of  Lamarck  and  Darwin,  and  those 
of  the  so-called  neo-Lamarckians 
and  neo- Darwinians  and  shows 
their  weak  points.  That  evolution 
takes  place  in  classes,  he  agrees  ; 
but  that  animals  and  plants,  for 
example,  have  a  genetic  relation- 
ship he  does  not  admit  :  "  the 
question  of  the  origin  of  animals 
from  plants  forms  no  problem  of 
the  hypothesis  of  evolution." 
The  polyphyletic  theory  of  evo- 
lution, held  by  his  brother  Jesuit, 
Fr.  Wasmann,  who  contributes  a 
I  section  on  ants  and  termites  and 
their  commensals — a  subject  on 
which  he  is  the  leading  authority 
— commends  itself  also  to  Father 
Frank. 


THE   THEOEY   OF   EVOLUTION 

IN   THE 

LIGHT   OF   FACTS 


Nihil  Obstat. 

Sti.  Ludovici,  die  19  Sept.,  1912 
JOSEPHUS  WENTKER 
Censor  Librorum. 

Imprimatur 

Sti.  Ludovici,  die  22  Sept.,  1912 
*    JOANNES  J.  GLENNON 

Archiepi scopus  Sti.  Ludovici. 


^M% 


THE 

THEORY   OF    EYOLUT 


IN   THE 


LIGHT  OF  FACTS 


BY 

KAKL  FBANK,  S.J. 

WITH   A   CHAPTER   ON  ANT    GUESTS  AND   TERMITE   GUESTS 

BY 

P.  E.  WASMANN 

TRANSLATED   FEOM  THE    GERMAN 

BY 

CHAELES  T.  DKUEKY,  F.L.S.,  V.M.H. 

VICTORIA  GOLD  MEDAL   OF  HONOUR 'IN   HORTICULTURE 


WITH    48    ILLUSTRATIONS 


LONDON 

KEGAN   PAUL,  TKENCH,  TKUBNEK  &  CO.  LTD. 
B.   HEBDER:     17    SOUTH     BBOADWAY,    ST.    LOUIS,    MO. 

1913 


PREFACE. 

THE  object  of  the  present  work  is  to  throw  some  light 
on  the  theory  of  Descent.  Among  many  of  the 
students  of  nature  of  the  present  day  we  perceive 
that  greater  and  greater  contradictions  arise  between 
the  actual  results  of  their  technical  work  and  that 
which  they  put  forward  as  '  postulates  9  of  the  theory 
of  Evolution.  Our  object  is  to  deal  with  this.  The 
'  certain '  or  the  '  probable '  should  be  separated 
from  the  pure  '  postulates  '  and  the  actual  area  of 
elucidation  of  the  hypotheses  of  Evolution  be  thereby 
clearly  defined.  The  chief  postulate,  the  origin  and 
development  of  the  animals  from  the  plants,  is  dealt 
with  fully. 

If  the  area  of  elucidation  be  exactly  defined,  then, 
and  then  only,  can  it  be  a  question  of  a  truly  scientific 
attempt  at  explanation.  The  best  known  systems, 
those  of  Darwin  and  of  Lamarck,  are  tested  by  their 
premisses  and  method  ;  but  only  their  specific  doctrines 
are  taken  into  consideration. 

In  the  formation  of  a  reliable  hypothesis  it  was 
less  important  to  present  a  complete  collection  of  all 
observations  than  to  show  clearly,  by  separate  examples, 
the  demonstrative  force  and  extent  of  the  argument 
concerned. 


vi  PEEFACE 

A  few  chapters  have  been  already  published  by 
the  Author,  but  in  another  connection— in  the  '  Lehr- 
buch  der  Philosophic/  3rd  ed.,  of  Father  Lehmen,  S.I. 
(published  by  Father  Peter  Beck,  S.I.).  Even  these, 
however,  have  been  partly  rewritten  and  extended. 

My  brother  in  the  order,  Father  E.  Wasmann,  has 
been  good  enough  to  place  at  my  disposal  a  contribution 
from  his  special  sphere  of  study.  Further  contributions 
regarding  similar  questions  he  will  himself  publish 
in  the  fourth  edition  of  his  work,  '  Die  Moderne  Biologic 
und  die  Entwicklungstheorie/  which  will  shortly 
appear. 

THE  AUTHOR. 

BALKENBURG. 


CONTENTS. 


PREFACE     . 

LIST  OF  ILLUSTRATIONS 


PAGE 
V 

xi 


SECTION  I. 

GENERAL  (PALJEONTOLOGICAL)  BASES  OF  THE  THEORY  OF 
EVOLUTION. 


CHAPTER  I. 

ORIGIN  OF  THE  PROBLEM  AND  DEFINITION  OF  QUESTIONS 
INVOLVED. 

1.  ORIGIN  OF  THE  PROBLEM     ...... 

2.  QUESTIONS  INVOLVED  ...... 

3.  CONCLUSIONS  FROM  CHAPTER  I     . 


1 

13 
15 


CHAPTER  II. 

RESULTS  OF  PALJEONTOLOGICAL  RESEARCH  INTO  THE  EVOLUTION 
OF  ORGANIC  LIFE. 

A.  PALJEONTOLOGICAL  RESULTS    .         .         .         .         .         .18 

§  1.  BRIEF  PURVIEW  OF  THE  CHRONOLOGICAL  SUCCESSION  OF  THE 

LARGER  ANIMAL  GROUPS 18 

§  2.  INTER-RELATIONS  BETWEEN  THE  GREATER  SYSTEMATIC  GROUPS 

(FAMILIES,  CLASSES,  AND  PARTLY  ORDERS)      ...       30 
§  3.  SOME  PAL^ONTOLOGICAL  '  LAWS  '  ACCORDING  TO  WHICH  THE 
TRANSFORMATION    PROCEEDED    WITHIN    DEFINED    (NAR- 
ROWER) GROUPS  (FAMILIES,  GENERA)    ....      34 

B.  RESULTS  OF  PAL^OBOTANY  (EVOLUTION  OF  THE  PLANT 

WORLD) 49 

§  1.  BRIEF  PURVIEW  OF  THE  CHRONOLOGICAL  SUCCESSION  OF  THE 

LARGER  PLANT  GROUPS  52 


viii  CONTENTS 

PAGE 

§  2.  INTER-RELATIONS  BETWEEN  THE  LARGER  GROUPS  (FAMILIES, 

SERIES,  AND  CLASSES)  .......  62 

§  3.  DESCRIPTION  OF  CHANGES  ACTUALLY  OBSERVED  AND  THE 
PROBABLE  CAUSES  OF  SAME  ('  PAL^ONTOLOGICAL  LAW 
OF  EVOLUTION') 65 


SECTION  II. 

THE  EXPLANATORY  DOMAIN  OF  THE  HYPOTHESIS  OF 
EVOLUTION. 

CHAPTER  I. 
INTRODUCTION     .........       77 

CHAPTER  II. 

LIMITATION  OF  THE  EXPLANATORY  DOMAIN  OF  THE  EVOLUTIONARY 

HYPOTHESIS. 

PRELIMINARY  OBSERVATION 83 

§  1.  WE    ARE    NOT    JUSTIFIED    IN    REGARDING    THE    ORIGIN    OF 
ORGANISMS   UPON   OUR  EARTH  AS   THE   RESULT   OF  AN 

EVOLUTIONARY  PROCESS 84 

§  2.  WE  ARE  NOT  JUSTIFIED  IN  BRINGING  ANIMALS  AND  PLANTS 

INTO  GENETIC  CONNECTION    ......     108 

§  3.  WE  ARE  NOT  JUSTIFIED,  IN  THE  PRESENT  STATE  OF  OUR  KNOW- 
LEDGE, IN  BRINGING  THE  FAMILIES  AND  CLASSES  OF  THE 
ANIMAL  AND  PLANT  WORLDS  INTO  GENETIC  CONNECTION  .     117 
APPENDIX  :  ARE  THERE  '  HIGHER  '  AND  '  LOWER  '  TYPES  ?  .     139 


SECTION  III. 
EVOLUTIONARY  HYPOTHESES. 

CHAPTER  I. 

THE  PRINCIPAL  ATTEMPTS  AT  EXPLANATION  HITHERTO. 

§  1.  LAMARCKISM  AND  NEO-LAMARCKISM       .....     145 
§  2.  DARWINISM  AND  NEO-DARWINISM          .         .         .         .         .157 


CONTENTS  ix 

CHAPTER  H. 

SUGGESTIONS  FOE  RELIABLE  HYPOTHESES  OF  EVOLUTION. 

§  1.  DIRECT  OBSERVATION  AND  THE  FACTS  OF  ANIMAL  AND  PLANT   PAGE 

GEOGRAPHY 164 

§  2.  SUGGESTIVE   POINTS   IN   THE   DOMAIN   OF  PARASITISM  AND 

SYMBIOSIS .        .        .177 

ANT  GUESTS  AND  TERMITE  GUESTS:    WASMANN    (ADAPTIVE 

PHENOMENA  IN  SYMBIOTICS)  .         .         .         .         .         .188 

§  3.  SUGGESTIVE  POINTS  IN  THE  EMBRYOGENY  OF   THE  PRESENT 

ORGANISMS  ........     202 

§  4.  SUMMARY  OF  THE  COLLECTED  RESULTS         ....     228 

CONCLUSION        .........    230 


INDEX 


237 


ILLUSTRATIONS. 

FIG.  PAGE 

1.    Lusus  NATURE 6 

2-4.             „ 8 

5.  RECONSTRUCTION  OF  PRIMARY  INSECT          ....  38 

6.  TRANSITIONAL  FORM  OF  INSECT  (CARBONIFEROUS)         .         .  39 

7.  BEETLE  (JURA) 40 

8.  WOOD  WASP  (JURA) 40 

9.  DRAGON  FLY  (JURA) 40 

10.  BEECH,  VARIOUS  STATES  OF  PRESERVATION  ....  50 

11.  PLANT  REMAINS  IN  SAMLAND  AMBER 51 

12.  RECONSTRUCTED  SIGILLARIA 54 

13.  TRUNK   OF   SIGILLARIA   SHOWING  VARIOUS   STATES   OF   PRE- 

SERVATION    54 

14.  LEPIDODENDRON  (RESTORED)        ......  56 

15.  CORDAITE  (RECONSTRUCTED)         .         .         .         ...         .56 

16.  RECONSTRUCTION  OF  TRUNK  OF  LYGINODENDRON  OLDHAMI- 

ANUM,   A  FERN-LIKE   GYMNOSPERM                .             .  57 

17.  SEED  OF  SAME 58 

18.  SEED-BEARERS  AND  NON-SEED-BEARERS  IN  THE  OLDER  PERIODS  59 

19.  CALAMITES  AND  ASTERO-CALAMITES      .....  66 

20.  FERN  VENATION  OF  SPHENOPTERIDIUM         ....  68 

21.  PINNATE  VENATION  OF  PECOPTERIS 69 

22.  RETICULATE  VENATION  OF  ALETHOPTERIS    ....  69 

23.  ARRANGEMENT  OF  LEAF  SCARS  ON  VARIOUS  SIGILLARIA         .  70 

24.  CALAMARIA  FOLIAGE 74 

25.  A  Moss  (Hyjmum  Purum) 122 

26.  NEPHRODIUM  filix  mas 124 

27.  POLLEN  GRAINS  .         .         .         .126 


xii  ILLUSTKATIONS 

FIG.  PAGE 

28.  SECTION  OF  EMBRYO  SEED  OF  GYMNOSPERM  (Picea  vulgaris)  .     126 

29.  FRUIT  BUD  OF  ANGIOSPERM  (Polygonum  convolvulus)  DURING 

FERTILIZATION:    POLLEN  GRAINS  AND  TUBES         .         .     127 

30.  HABIT  OF  EQUISETUM  (E.  arvense)       .....     128 

31.  HABIT  OF  CLUB-MOSS  (Lycopodium  clavatum)         .         .         .129 

32.  PLANARIA 184 

33.  DISTOMUM 185 

34.  COPEPODA  ..........     186 

35.  LOMECHUSA  STRUMOSA  F.  190 

36.  TERMITOBIA  ENTENDVENIENSIS     .         .         .         .         .         .191 

37.  PHYSOGASTRE  IMAGO  OF  Termitoxenia  Assmuihi   .         .         .     195 

38.  ECITOPHYA  SlMULANS  .         .         .         .         .         .         .198 

39.  BARNACLE,  FORMS  OF  DEVELOPMENT     .....     204 

40.  CIRRIPEDIA          .........     206 

41.  SACCULINI  CARCINI  ATTACHED  TO  Carcinus  Mcenas       .         .     207 

42.  YOUNG  FLOUNDER;    EYES  ON  EACH  SIDE     .         .         .         .208 

43.  FLOUNDER  GROWN;  BOTH  EYES  ONE  SIDE    ....     208 

44.  TURBOT,  SHOWING  EYES  IN  TRANSIT     .....     208 

45.  TURBOT 210 

46.  MEADOW  LIZARD  ;  EFFECTS  OF  HEAT   .         .         .         .         .212 

•47.    GREENLAND  WHALE  215 

48.  PEDIGREE  CHART  OF  BEETLE  FAMILY           .         .         .  face  p.  228 


THE   THEORY  OF   EVOLUTION   IN 
THE  LIGHT  OF  FACTS. 

SECTION  /. 

GENEKAL  (PAL^EONTOLOGICAL)  BASES  OF  THE  THEOEY 
OF  EVOLUTION. 

CHAPTEE  I. 

OKIGIN    OF    THE     PROBLEM    AND     DEFINITION     OF 
QUESTIONS    INVOLVED. 

§  1.  Origin  of  the  problem. 

A  STUDY  of  the  organic  world  in  which  we  live  demon- 
strates clearly  that  the  animals  and  plants  do  not  show 
a  confused  admixture  of  forms  but  display  a  separation 
into  groups  which  can  usually  be  defined  with  sufficient 
certainty.  We  find  individuals  which  among  them- 
selves are  fairly  alike  in  all  characters  and  which  under 
normal  circumstances  can  also  only  be  perfectly  fertile 
by  intercrossing.  The  whole  of  these  individuals  which 
are  so  related  to  each  other  form  a  so-called  systematic 
species.  The  Wolves,  for  instance,  form  such  a  species 
(Canis  lupus  L.).  That  by  the  word  '  wolf '  we  represent 
a  defined  type  of  animal  which  cannot  be  confounded 
with  another  is  shown  by  the  pictures  in  our  school- 
books  and  primers  by  which  the  children  are  made 


2  THE  THEORY  OF  EVOLUTION 

acquainted  with  this  dreaded  animal.  A  single  picture 
is  there  indicated  with  the  name  of  'The  Wolf '  beneath 
it,  and  yet  it  is  expected  that  the  child  will  recognize 
by  this  single  picture  all  wolves  which  it  might  ever 
see  in  any  zoological  garden. 

Similar  animals,  but  not  wolves,  are  the  Dogs,  wild 
and  tame,  and  the  Foxes.  The  make  of  the  paws,  the 
toes,  the  entire  habit  and  mode  of  life  ( Garni vora)  are 
very  similar  ;  on  the  other  hand  they  differ  entirely 
in  all  these  characters  from  the  Sheep,  Goats,  etc.  On 
the  strength,  therefore,  of  the  said  similarities  the  wolf, 
dog,  fox,  etc.,  are  placed  in  a  higher  systematic  unit, 
viz.  in  the  dog  family  of  the  Canidse.  Particularly  in 
the  shape  of  the  jaw  (carnivorous  jaw)  all  dog-like  animals 
resemble  the  Bears,  the  Marten,  and  others ;  all  these 
animals  can  therefore  be  united  to  a  further  group, 
viz.  that  of  the  land  Carnivora  (Carnivora  fissipedia). 
According  to  the  similarities  which  even  then  remain 
between  many  groups,  the  allocation  of  animals  to 
higher  units  progresses,  which  naturally  then  become 
ever  more  and  more  general  and  comprehensive.  The 
land  Carnivora  are  united  with  the  aquatic  Carnivora 
(Pinnipedia)  to  form  the  order  of  Carnivora ;  then 
with  all  sucking  animals  to  form  the  class  of  Mam- 
malia ;  and  finally  with  all  animals  which  possess  a 
skeleton  formed  of  jointed  vertebrae,  to  form  the 
tribe  of  Vertebrates. 

It  is  now  a  question  whether  this  graduated  division, 
which  renders  it  possible  for  us  to  unite  all  animals 
and  plants  into  a  few  tribes  and  classes,  is  only  the 


ORIGIN  OF  THE  PROBLEM  3 

expression  of  a  general  plan  which  the  Creator  wished 
once  and  for  all  to  realize,  or  whether  this  similarity 
rests  really  upon  actual  relationship  (blood-relationship). 
We  can  easily  come  to  the  latter  conclusion,  since  in 
point  of  fact  we  observe  that  the  greater  the  resem- 
blance between  definite  individuals  so  much  the  closer 
is  the  true  blood-relationship.  Children,  as  is  often  said, 
resemble  the  parent  like  '  their  very  image/  and  brothers 
and  sisters  are,  as  between  themselves,  of  the  greatest 
similarity.  Negroes,  Indians,  Chinese  are  also  '  true ' 
men  and  resemble  the  Europeans,  but  the  reason  of 
their  perfect  racial  resemblance,  which  is  shown  by  the 
Negro,  we  seek  and  find  again  in  their  descent  from 
black  parents,  in  their  close  or  more  distant  blood- 
relationship.  Ought  we  or  must  we  therefore  also,  in 
order  to  explain  that  Europeans,  Negroes,  Indians,  etc., 
are  all  men,  accept  a  common  descent  for  all  and 
therefore  an  actual  blood-relationship,  even  though 
it  be  a  cousinship  1000  or  10,000  degrees  removed  ? 

The  same  question  can  also  be  raised  in  view  of  the 
similarity  of  the  systematic  hierarchy  established  for 
animals  and  plants.  Is  every  resemblance,  be  it  ever 
so  trifling — as,  for  instance,  the  possession  of  a  vertebral 
column — the  expression  of  an  actual  blood-relationship, 
or— what  is  the  same  thing— the  descent  from  common 
progenitors  in  the  dim  and  distant  past  ? 

The  question  cannot  obviously  be  determined  a 
priori  nor  even  by  the  direct  observation  of  the  animal 
and  plant  forms  of  the  present  day.  We  observe, 
indeed,  that  blood-relationship  (descent  from  the  same 

B  2 


4  THE  THEOKY  OF  EVOLUTION 

parents)  never  establishes  a  more  general  or  more 
extended  similarity  than  the  '  specific  similarity ' : 
that  is,  the  most  perfect  similarity  which  we  in  fact 
know  of.  Progeny  of  the  same  parents  never  depart 
so  far  from  each  other  or  even  from  their  nearest 
'  relatives '  that  we  rank  them  of  different  species, 
and  therefore  we  must  create  a  '  race '  for  all  of 
them  in  order  to  unite  them  generally.1 

Upon  this  observation  the  opinion  is  based  that 
the  specific  similarity  is  above  the  expression  of  actual 
relationship — which  specific  similarity  is  always,  so  far 
as  we  can  observe  it,  transmitted  unchanged  as  regards 
the  essential  distinct  characters  in  the  process  of 
reproduction,  i.e.  remains  constant  :  that  would  be 
the  doctrine  of  specific  constancy. 

The  greater  or  less  similarity  also  with  other  animal 
types  was  well  recognized,  but  since  it  was  seen  how 
they  continued  to  exist  together  but  separated,  and 
crossed  either  never  or  unwillingly  or  unfruitfully, 
it  struck  no  one  that  similarity,  carried  further,  could, 
and  must,  be  based  on  descent. 

Already  the  attention  of  some  investigators  had 
been  aroused  by  certain  petrifactions.  Many  of  these 
showed  clearly  the  form  of  mussels,  fish,  leaves,  etc., 
but  they  often  appeared  quite  different  from  the  corre- 
sponding animals,  etc.,  with  which  man  was  familiar. 
Sea  mussels  and  sea  fish  were  also  found  far  inland  or 

1  We  choose  this  mode  of  expression  purposely,  which  moreover  cannot 
be  contested,  in  order  to  avoid  long  explanations  as  to  the  meaning  of 
'  species.'  Compare  Wasmann  :  Die  Moderne  Biologie  und  die  EntwicUungs- 
iheorie,  chap.  x. 


ORIGIN  OF  THE  PROBLEM  5 

even  on  the  mountains.  Endeavours  were  made  to 
explain  this  in  very  varied  ways,  either  by  acceptance 
of  oceanic  floods  which  carried  the  sea  animals  inland, 
or  it  was  disputed  that  they  were  really  the  remains 
of  pre-existent  life. 

To  this  end  a  peculiar  force  in  stone  was  conceived — 
nisus  formativus,  or  petrif active  force — which,  with  or 
without  the  assistance  of  the  stars,  imitated  organic 
forms  from  inorganic  materials. 

This  opinion,  in  the  sixteenth  and  seventeenth 
centuries,  was  the  ruling  one  despite  the  better  know- 
ledge of  some  eminent  men. 

Leonardo  da  Vinci,  for  instance,  would  have  nothing 
to  do  with  such  enigmatical  working  of  the  constellations. 

Since,  however,  it  was  considered  that  the  earth 
and  its  organisms  had  been  created  as  they  then  were, 
the  nisus  formativus  appeared  to  be  the  more  accept- 
able explanation.  Consequently  the  '  petrifactions ' 
were  not  at  all  regarded  as  the  remains  of  organisms 
which  at  one  time  had  really  lived  ;  and  of  a  connec- 
tion with  the  living  animals  and  plants  of  to-day  no 
one  then  thought.  The  opinions  of  the  time  are  shown, 
for  instance,  in  A.  Kircher's  '  Mundus  subterraneus  ' 
(Figs.  1-4). i 

Since,  however,  the  number  of  such  '  figure  stones  '. 
discovered  constantly  increased,  grave  doubts  began 
to  arise  against  the  nisus  formativus  theory,  especially 

1  II,  Amstelodami  1665,  c.  9.  Kircher  also  stated  that  many  of  these 
lusus  naturae  might  have  originated  through  hollow  spaces  in  the  earth 
becoming  filled  with  mud. 


6  THE  THEORY  OF  EVOLUTION 

since  it  apparently  had  ceased  to  act.  The  conclusion 
became  enforced  that  the  petrifactions  should  be  con- 
sidered as  remains  of  actual  organisms  which,  however, 
certainly  had,  in  the  opinion  of  the  time,  nothing  to  do 
with  the  still  existent  forms  of  animal  and  plant  life  ; 
they  were  extinct,  i.e.  types  of  life  which  had  been 
annihilated  by  the  one  universal  flood,  the  Noachian 
Deluge. 


FIG.  1. — LTTSUS  NATURAE. 

Obviously  fancifully  completed.      Fig.  2  is  based  on  a  mussel 
(Inoceramus).      (After  A.  Kircher.) 

The  most  formidable  upholder  of  this  view  was 
undoubtedly  J.  J.  Scheuchzer  (1672-1733).  He  took 
up  arms  courageously  against  the  current  ideas  of 
aerial  spirits  (Archaei)  which  bury  themselves  in  the 
soil  and  stones  and  so  shape  organic  forms.  *  Such 
idols/  he  says  in  his  book  'Homo  diluvii  testis/  f  must 
be  overthrown  and  destroyed,  not  so  much  by  subtle 
philosophy  and  all  sorts  of  brain  whims,  but  by  presen- 
tation and  observation  of  Nature's  bodies  themselves, 


ORIGIN  OF  THE  PROBLEM  7 

and  such  resulting  consequences  as  even  the  simplest 
may  seize  on  and  understand.  Nature  must  be  her 
own  advocate,  and  wisdom,  though  unstudied,  must  be 
the  judge/  He  also  expressed  himself  strongly  against 
the  lusus  naturce.  In  his  paper  Piscium  querelce  et 
vindicice  (1708)  he  makes  the  Fishes  raise  objections 
that  they  are  not  considered  as  the  original  parents  of 
the  present  fishes  but  are  regarded  as  of  '  mineral  stone 
and  marl  births/  l 

In  his  splendid  work '  Physica  sacra ' 2  he  goes  through 
the  separate  groups  of  animals  which  were  destroyed 
by  the  Flood.  His  copperplates  are  excellent,  his 
added  verses  less  so.3 

With  regard  to  the  origin  of  the  mountain  ranges 
he  had  also  some  wonderful  ideas.  When  the  Gemusz 
(vegetable  debris),  into  which  the  earth's  strata  had  been 
changed  by  the  Flood,  dried  again,  the  crust  burst  and 
there  were  heavings  and  sinkings.  That  earthquakes 
and  the  like  had  been  able  to  form  the  Alps  was,  in  his 
idea,  a  '  lame  opinion/ 

1  K.  v.  Zittel :    Geschichte  der  Geologie  und  Paldontologie  bis  Ende  des 
19  Jahrhunderts,  Munich-Leipzig,  1899,  24. 

2  I,  p.  61,  Augsburg  und  Ulm,  1731. 

3  Since  he  found  remains  of  all  animal  forms,  he  deduced  that  all 
animal  life  was  annihilated,  and,  from  that,  that  the  Deluge  was  universal : 

'  Since  all  that  lived  and  moved  therein  was  drowned 
'Tis  clear  the  Flood  prevailed  the  whole  world  round.' 

(p.  64,  Translation.) 

'  The  man  of  evil  luck's  remains  likewise  from  out  the  ground 
Have  now  been  dug,  and  for  it  many  reasons  have  been  found.' 

(p.  66,  Translation.) 

This  '  man  of  evil  luck  '  ('  a  disturbed  skeleton  of  an  old  sinner  ')  even- 
tually proved  to  be  the  skeleton  of  a  gigantic  Salamander  (now  in  Haarlem). 


8  THE  THEORY  OF  EVOLUTION 

The   Noachian   Deluge   was   made  responsible  for 


FIGS.  2-4. — Lusus  NATURE. 
Fish  skeletons  completed.     (After  A.  Kircher.) 

everything.     That  the  earth's  strata  could  be  formed 
by  quiet  deposit   of  flooded  materials  such  as   sand 


ORIGIN  OF  THE  PROBLEM  9 

and  mud,  as  now  happens,  he  had  no  conception. 
As  regards  the  causes  of  elevation  and  depression  and 
the  significance  of  volcanic  catastrophes  the  proper 
understanding  failed  him  entirely. 

But  this  point  of  view  likewise  failed  to  be  per- 
manently maintained.  It  was  gradually  recognized 
that  the  separate  and  sharply  denned  strata  concealed 
varied  fauna  and  flora  in  their  depths.  There  must, 
therefore,  have  happened  several  such  mighty  floods, 
or  catastrophes  of  other  kinds — the  living  world  was 
annihilated  repeatedly  and  arose  again  as  often.  Since, 
however — precisely  because  they  often  varied  greatly 
from  each  other — no  one  conceived  the  thought  that 
the  separate  successive  organic  forms  might  derive 
their  origin  from  each  other  by  descent,  nothing  remained 
but  to  explain  each  new  organic  world  by  a  new  creation 
or  successive  creation. 

It  was  not  every  investigator  who  understood  by 
c  new  creation '  a  creative  act  of  God.  Cuvier,  who  often 
used  the  word,  assumed  that  after  the  destruction  of  a 
defined  fauna  a  new  one  immigrated  from  somewhere, 
so  that  in  this  way  a  new  creation,  i.e.  new  creatures, 
took  the  place  of  the  extinct  ones.  Cuvier,  however, 
had  no  idea  of  a  genetic  connection  (by  descent) 
between  the  successive  and  varied  organisms.1 

Cuvier's  pupils,  d'Orbigny,  d'Archiac  and  others, 
carried  their  master's  teaching  further :  d'Orbigny 3 

1  Compare  Chr.  Deperet :  Die  Umbildung  der  Tierwelt,  Stuttgart,  1 909, 10 
(German  translation  by  R.  N.  Wegner  of  the  French  work,  Les  Transfor- 
mations du  Monde  Anitnal,  by  Chr.  Deperet). 

2  Cours  JUlementaire  de  Palfjeontologie  Stratigraphique,  II,  Paris,  1849,  251. 


10  THE  THEOKY  OF  EVOLUTION 

established  twenty-nine  quite  different  creations,  each 
quite  independent  of  the  other,  which  owed  their 
existence  rather  to  twenty-nine  different  acts  of 
creation.  This  happened  so  late  as  the  year  1849. 

1  A  first  creation/  said  d'Orbigny,  '  shows  itself  in 
the  Silurian  formation.  After  the  entire  destruction 
of  this  by  some  geological  cause,  and  after  expiry 
of  a  considerable  period,  there  occurred  a  second  crea- 
tion in  the  Devonian  formation  and  thereafter  twenty- 
seven  successive  and  different  creations  have  repeopled 
the  whole  earth  with  plants  and  animals  in  connection 
with  the  geological  cataclysms  which  had  previously 
destroyed  all  living  nature.  These  are  facts,  certain 
but  incomprehensible  facts,  which  we  confine  ourselves 
to  stating  without  attempting  to  pierce  the  super- 
terrestrial  secret  which  enfolds  them/  x 

We  point  out  that  such  eminent  men  as  Cuvier  (the 
father  of  Palaeontology)  and  his  pupils  found  the 
separate  successive  organic  worlds  so  fundamentally 
different  from  each  other  that  they  conceived  abso- 
lutely no  idea  that  the  later  ones  could  arise  from  the 
former.  Therefore  no  one  either  can  or  should  doubt 
any  longer  that  the  organisms  really  appeared  different 
in  the  past  than  they  do  now,  and,  moreover,  the  com- 
parative difference  is  the  greater  the  older  they  are. 
Both  facts  are  established  by  investigators  who  had 
no  interest  whatever  that  it  was  so  ;  rather  did  it 
confuse  them  to  be  thus  confronted  with  '  incompre- 
hensible facts/ 

1  Deperet-Wegner  :  Die  Unibildung  der  Tienvelt,  p.  15. 


OKIGIN  OF  THE  PEOBLEM  11 

D'Orbigny  might  well  feel  that  the  acceptance  of 
twenty-nine  complete  destructions  and  complete  new 
creations  involved  something  unworthy  of  credit.  The 
number  was  also  arbitrarily  chosen.  If  the  organisms 
were  always  so  unchangeable  as  they  appear  to  be  now, 
then,  as  a  consequence,  new  creations  must  be  accepted 
and  also  the  time  between  each  two  catastrophes ; 
since  many  animal  types  show,  on  one  and  the  same 
geological  strata-system,  such  changes  as  the  theory  of 
'  specific  constancy  '  cannot  admit. 

Why,  furthermore,  do  the  new  creations  so  often 
approach  the  extinct  forms  so  closely  that  in  many 
cases  the  conclusion  forces  itself  upon  us,  that  the  im- 
mediately successive  creation  must  be  a  simple  further 
development  of  that  immediately  preceding  ?  That  is 
particularly  the  case  when  in  the  immediately  preceding 
creation  the  organisms  already  show  clear  traces  of 
changes  in  a  definite  direction,  which  need  be  only 
increased,  i.e.  further  differentiated,  in  order  to  perfectly 
explain  the  appearance  of  the  immediately  succeeding 
animal  and  plant  creation.  Furthermore,  the  geologist 
in  the  meantime  had  recognized,  by  more  exact  observa- 
tion of  the  geological  formations  and  denudations  of 
the  present  day,  that  the  fossil-bearing  strata  could 
not  have  originated  catastrophically.  At  the  most 
such  an  explanation  can  only  be  applied  to  particular 
local  changes.  Lyell  especially  has  the  merit  of  this 
more  natural  comprehension  of  the  terrestrial  forma- 
tions ('  Principles  of  Geology/  1st  ed.  1830-38). 

It  will,  therefore,  be  willingly  conceded  that  the 


12  THE  THEtfcY  tF  EYtL¥TItN 

'  catastrophic '  and  '  creation '  theories  do  not  afford 
the  most  natural  explanation  of  the  history  of  life 
lijDon  the  eaftnT"  Another  hypothesis  was,  however, 
still  impossTBIe^sD  long  as  the  absolute  unchangeability 
of  the  organisms  was  adhered  to. 

Already,  in  Curier's  lifetime  for  the  first  time,  serious 
attacks  began  tt  lie  made  on  the  '  constancy '  theory 
in  trier  to  permit  the  possibility  tf  amatier  significa- 
tion being  given  t«  palsetnttltgical  facts,  and  particu- 
larly to  establish  an  attmal  collection  between  the 
present  and  fossil  organisms.  Lamarck  and  Geoffrey 
St.  Hilaire  had  already,  decades  before  the  appearance 
of  d'*§rbigny's  '  Cours  elementaire/  put  forward  theories 
on  quite  new  and  unheard-of  lines.  But  their  ideas 
found  no  proper  response  among  their  contemporaries. 
It  was  reserved  for  Charles  Darwin  to  obtain  for  the 
new  doctrine  a  general  acceptance  :  in  what  sense  that 
should  be  properly  understood  we  shall  speedily  see. 

All  agreed  that  the  living  and  fossil  animal  and 
plant  forms  are  connected  genetically,  i.e.  by  descent. 
Thus  the  many  new  creations  became  superfluous. 
These  were,  indeed,  only  insisted  upon  because  that 
connection  was  denied.  The  difference  established 
by  palaeontology  of  offspring  between  themselves 
and  from  their  ancestors  finds  its  explanation  in  the 
variability  of  the  organisms,  which,  in  the  sharpest 
contradiction  to  the  '  constancy  theory/  became  re- 
garded as  a  fundamental  quality  of  all  living  things. 
Since  palaeontology  furthermore  presented  some  evi- 
dence that  the  difference  of  form  of  the  progeny  was 


•RIGIN  tF  TME  PRtBLEM  13 

accompanied  by  a  certain  degree  of  improvement  in 
the  sense  of  development  (evolution)  of  previously 
existing  points,  the  new  hypotheses  were  termed 
'  evolutionary  hypotheses/  Brolution,  therefore,  implies 
more  than  change  of  form.  The  French  scientists, 
especially  palaeontologists,  frequently  use  up  to  the 
present  the  word  f  transformism  '  or  '  transformation  ' : 
thus  the  excellent  work  of  Ok.  Beperet  (1909)  bears 
the  title  of  '  Les  Transformations  du  Monde  Animal/ 
the  German  translation  ky  Wegner  tkat  of  '  Bie 
Wmbildung  der  Tierwelt '  (a  literal  translation). 

§  t.  Questions  inched. 

If  we  wonld  now  come  to  a  decision  regarding  the 
history  of  organic  life,  tkem,  according  t*  the  above, 
the  f  •lowing  ^mesti^ns  must  Tie  put  aid.  answered  in 
the  give*  se«ji.emce  : 

(1)  I«  tkere  a  general  genetic  connection  between  the 

•rgaaisHBLS  tf  t*-4aj  and  the  fossilized  ones  ? 
If  jes,  them  we  accept  without  furtker  argument 
a  fkauge,  a  transformation  of  the  organism,  since  the 
oli  animal  aid   plait   worlds  appeared  different  from 
the  younger  and  present  oies. 

(2)  Is  this  change,  this  transformation,  connected 

with  a  higher  development  ? 

This  question  cannot  possibly  be  decided  unless 
we  know  what  palaeontology  teaches  us  : 

(a)  With  regard  to  the  succession  of  definite  well- 
characterized  groups  (types). 


14  THE  THEOKY  OF  EVOLUTION 

(b)  With  regard  to  the  genetic  connection  of  the  later 

(higher)  groups  with  the  earlier  (lower)  ones. 

(c)  With   regard   to    the    eventual   changes   within 

such  groups. 

If  the  so-called  higher  groups  follow  the  lower  but 
do  not  arise  through  them  then  we  have  no  higher 
evolution  in  the  narrow  sense  of  the  word,  because 
then  the  entire  transformation  effects  itself  within  the 
same  plane  of  organization,  for  example,  within  the 
same  order. 

If  we  come  to  a  definite  conclusion  regarding  these 
three  questions,  then,  and  not  before,  can  we  think  of 
formulating  an  hypothesis  which  will  explain  or  make 
comprehensible  that  which  has  been  demonstrated  or 
accepted  as  probable. 

Whoever  accepts  the  genetic  connection  of  all  living 
things  1  must  seek  for  an  '  hypothesis  of  descent/  and 
since  with  the  genetic  connection  a  transformation  is 
essential,  also  an  '  hypothesis  of  transformation  '  must 
be  sought  for.  Whoever  in  addition  accepts  a  higher 
development  needs  an  '  hypothesis  of  evolution '  if 
he  will  explain  everything.  In  point  of  fact  the 
expressions  '  evolution/  '  transformation/  '  descent ' 
become  less  strictly  separated.  Furthermore  the  terms 

1  It  is  naturally  here  an  entirely  general  question  whether  we  can 
accept,  as  a  rule,  a  connection  between  present  types  and  those  of  earlier 
times  of  different  appearance.  To  inquire  which  organisms  thereby  come 
under  consideration  is  a  matter  for  the  palaeontologist.  For  man,  by 
reason  of  his  essentially  higher  elevation  over  the  whole  of  the  rest  of  living 
beings  (the  spirituality  of  the  soul),  there  must  be  accepted,  in  any  case,  a 
special  intervention  of  God.  For  man,  if  he  be  taken  as  a  whole,  no 
beast  can  be  regarded  as  ancestor,  however  highly  it  may  be  developed. 


ORIGIN  OF  THE  PROBLEM 


15 


used  to  indicate  the  scientific  value  of  the  endeavours 
at  explanation,  '  hypotheses/  '  theories/  or  even  '  doc- 
trines/ are  constantly  changing.  We  believe  that  the 
expression  *  theory  of  evolution '  best  fits  the  present 
position  of  the  scientific  world.  We  will,  however, 
use  the  other  expressions  as  opportunity  demands. 

A1]_}iypnf,V>p.aes  must  ^according  to  the  scientific 
principles  generally  followed,  start  from  the  present 
observation  of  the  organisms  concerned,  and  may  not, 
as  a  basis  of  explanation,  combine  therewith  anything 
which  is  contradictory  to  the  certain  teachings  of  other 
sciences,  especially  that  of  philosophy.  They  must 
furthermore  state  precisely  what  they  really  claim  to 
explain  and  therefore  must  above  all  things  adhere 
to  the  results  of  paleeontological  research. 


§  3.  Conclusions  from  Chapter  I. 

As  is  seen  from  the  above,  it  is  not  a  question  in 
this  chapter  of  a  positive  proof  of  a  descent  of  the 
present  organic  forms  from  earlier  ones.  A  genetic 
connection  is  only  accepted  in  order  to  avoid  what_ 
is  regarded  as  an  unnatural  presentation  of  repeated 
annihilations  and  new  creations  of  entire  organic  worlds. 
TChedifficulty  in  winch  investigators  were  placed  by  the 
catastrophic  theory  has  become  greater  and  greater 
since  fossils  were  discovered  in  the  deepest  strata, 
while  even  within  the  compass  of  single  formations 
changes  were  observed  in  certain  animal  and  plant 
groups,  and  particularly  since  geological  processes  of 


16  THE  THEORY  OF  EVOLUTION 

the  present  time  have  been  ascertained  which  can  fully 
explain  the  origin  of  fossiliferous  formations  without 
any  great  catastrophic  cause  at  all. 

Neither  philosophy  nor  theology  compels  us  to 
accept  any  such  hypothesis  of  creation  as  involves,  for 
instance,  that  God  destroyed  all  fishes  twenty-nine  times 
(d'Orbigny)  and  created  them  anew  twenty-nine  times, 
the  newly  created  differing  generally  more  or  less  from 
the  destroyed  ones  while  some  were  replaced  almost 
unaltered. 

The  only  objection  which  could  be  raised  was  the 
following :  It  is  not  necessary  to  assume  that  the 
present  forms  descend  from  others  of  different  appear- 
ance, but  from  like  or  very  similar  forms  which  previously 
existed  near  the  differing  ones,  the  remains  of  which 
have  so  far  not  been  discovered.  In  that  case  the 
'  catastrophic  '  theory  would  also  be  superfluous,  and 
despite  it  a  so  thorough  transformation  of  the  organisms 
should  not  be  accepted  as  established,  since  experience 
now  appears  to  contradict  it. 

Next  there  should  be  remembered  the  words  of 
d'Orbigny  regarding  the  '  complete  '  divergence  of  the 
earlier  forms  from  those  of  to-day,  which  were  not 
shaken  even  by  some  examples  of  striking  constancy 
within  very  narrow  limits  of  relationship,  which  have 
continued  from  the  oldest  periods  to  the  present.  How 
the  unchangeability  of  living  organisms  is  to  be  regarded 
we  shall  consider  later  on.  For  the  rest  it  is  inexplic- 
able how  precisely  those  differently  formed  animals 
and  plants  in  the  strata  accessible  to  us  have  been 


ORIGIN  OF  THE  PROBLEM 


17 


preserved,  while  those  similar  to  the  present  ones,  but 
which  mostly  lived  together  with  them  under  the 
same  conditions,  are  generally  rare. 

The  objection  that  most  fossils  lie  at  the  bottom  of 
the  sea  and  cannot  be  examined  by  us  at  all,  does 
not  help  us  out  of  this  difficulty.  Thereby  we  could 
'  demonstrate  '  everything. 

We  are  therefore  inclined  to  accept  a  connection  [ 
by  descent  between  the  present  and  the  fossil  organisms,  \ 
because  this  assumption  is  the  more  natural  provided   \ 
that  the  observation  of  the  present  organisms  does  not 
exclude  such  an  hypothesis. 

The  object  of  earnest  scientific  investigation  would 
be  to  examine  more  closely  the  present  forms  of  organic 
life  as  regards  their  varietal  capacity  and  to  follow  up  I  •• 
the  evolutionary  series  of  the  separate  groups  and  no 
longer  to  maintain  in  a  merely  general  way  a  genetic- ' 
connection  as  a  postulate.  This  work,  especially  the 
palseontological  side  of  it,  has  been,  however,  only 
resumed  in  recent  years  on  really  unprejudiced  lines. 
To  this  we  owe  the  really  natural  further  development 
of  the  question  of  descent  which  for  some  decades  had 
been  interrupted  by  hypotheses  of  a  merely  general 
character. 


CHAPTEE  II. 

RESULTS     OF    PAL^EONTOLOGICAL    RESEARCH     INTO     THE 
EVOLUTION    OF    ORGANIC    LIFE. 

A.— PALJEONTOLOGICAL  RESULTS. 

§  1.  Brief  purview  of  the  chronological  succession  of  the 
larger  animal  groups. 

FOSSILS  are  exclusively  found  in  the  so-called  sedi- 
mentary deposits  which  form  the  upper  part  of  the 
earth's  crust.  Sediments  (sedimentary  or  secondary 
formations)  are  such  rocks,  nearly  always  appearing  as 
layers,  which  by  deposit  of  gravel,  sand,  or  mud  (or 
by  decomposition  of  dissolved  minerals — salts  for 
instance),  are  formed  in  the  greater  water-basins  (in  the 
sea  or  fresh-water  lakes).  The  foundation  of  investiga- 
tion of  the  origin  of  organisms  is  therefore  an  exact 
determination  of  the  age  of  the  sediments.  It  is  only 
when  it  is  known  which  stratum  or  layer  (a)  is  older  or 
younger  than  another  (b)  that  we  can  also  know  which 
organisms  are  older  or  younger  than  others  accordingly. 
This  determination  of  the  age  of  the  earth's  strata  is, 
however,  a  very  difficult  matter,  and  the  course  of  evi- 
dence which  led  to  the  generally  recognized  arrangement 
of  the  four  (or  five)  groups  of  formations,  is  not  far 
removed  from  a  vicious  circle,  especially  when  we 


KESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     19 

consider    the    mode    of    expression    used    by    many 
authors.1 

The  uncertainty  which  exists,  if  we  accept  the  usual 
division  into  separate  groups  determined  by  age,  may 
be  judged  by  the  following  short  consideration  :  If 
it  be  no  longer  a  question  whether  the  organisms  gener- 
ally vary,  but  rather  how  they  transformed  themselves, 
then  it  is  not  sufficient  to  compare  formations  differing 
considerably  in  age,  but  those  immediately  following 
each  other  must  be  known,  since  it  is  only  when  it  is 
known  which  formation  was  the  next  to  be  deposited, 
that  the  further  fate  of  a  definite  organic  group  can 
be  properly  followed  up  without  a  break.  Then  next 
younger,  which  we  will  call '  b/  need  not  necessarily  be 
deposited  over  stratum  '  a '  which  has  just  been  formed, 
but  may  originate  in  quite  another  region.  The  stratum 
e  a '  can,  for  instance,  become  dry  land  by  the  retreat  of 
the  sea  in  which  it  was  formed.  The  sea  itself  departs, 
together  with  its  organisms,  which  hitherto  had  been 
buried  in  'a/  to  some  other  region  and  there  deposits  the 
successors  of  the  organisms  buried  in  "a/  If  there  be 
no  means  of  recognizing  this  next  younger  deposit, 
or  if  it  be  again  covered  by  the  sea,  then  nothing  can 
be  said  regarding  the  evolutionary  progress  of  such  a 
group,  or  at  least  there  exists  a  gap.  Then  it  may 
happen  that  the  animal  groups,  which  we  learnt  to 
recognize  in  the  strata  complex  'a/  in  that  deposit  (' c ') 

1  Compare  the  methods  of  age-determination  by  E.  Kayser  (Lehrbuch 
der  Oeolog.  Formationskunde,  Stuttgart,  1909,  p.  2) ;  and  also  the  Introduc- 
tion of  M.  Neumayr,  Erdgeschichte  II. 

c2 


20  THE  THEORY  OF  EVOLUTION 

in  which  we  meet  them  again  for  the  first  time,  show  an 
entirely  peculiar  appearance,  so  that  at  the  first  glance 
no  one  would  think  of  any  connection  with  the  fauna 
of  ( a/  If,  however,  the  groups  of  formation  '  a  '  show 
a  distinct  tendency  to  vary  in  a  definite  direction,  and 
if  from  a  comparison  of  the  fauna  of  '  c  '  with  that  of  '  a ' 
it  is  seen  that  the  heterogeneousness  consists  in  a  great 
but  apparently  interposed  increase  of  just  those  varia- 
tional  tendencies  evinced  in  '  a/  then  it  may  be  assumed 
with  great  probability  that  the  organisms  in  '  c  '  are  the 
modified  offspring  of  those  of  '  a/  The  intermediate 
links  lie  buried  in  '  b/  and  this  formation  is  possibly 
now  and  has  been  for  a  long  period  covered  with  water 
and  therefore  inaccessible  to  us.  The  same  process  can 
also  be  repeated  for '  c/  One  of  the  fauna  of. '  c 3  approxi- 
mating thereto,  but  greatly  modified,  may  for  instance 
only  be  found  again  in  an  obviously  much  younger 
formation,  say  in  '  f /  and  this  may  be  in  North  America 
while  '  c '  may  be  in  Europe.  (The  strata  (  d '  and  '  e '  lie 
perhaps  under  water  or  have  not  been  investigated.)  If 
we  accept  a  connection  between  '  f/  '  c/  and '  a/  then  we 
have  obviously  only  important  outposts  as  it  were  in 
the  march  of  evolution  of  a  particular  group,  and 
perhaps  also  a  general  indication  how  the  outpost  '  f ' 
can  have  been  derived  from  '  c '  and  '  a/  but  without 
any  precise  knowledge  of  the  process  involved. 

Only  in  a  few  cases :  as,  for  example,  the  same  sea 
in  which  the  formation  '  a '  was  deposited,  may,  in  a 
short  time,  return  to  its  old  position  (sea  oscillations), 
and  consequently  the  same  organisms  also  return,  so 


KESULTS  OF  PAL.EONTOLOGICAL  RESEARCH     21 

that  in  the  stratum  '  b  '  which  is  formed  after  the  return 
we  have  before  us  the  immediate  descendants  of  'a/ 
Several  such  cases  can  be  recognized  with  sufficient 
certainty.  Then  by  comparing  '  b  '  and  '  a '  we  arrive 
under  certain  circumstances  at  a  clear  insight  into 
the  mode  of  variation  and  its  rapidity,  etc. 

If  the  fauna  of  '  a/  or  a  group  of  the  same,  should 
not,  generally  speaking,  reappear,  and  is  no  longer 
seen  at  the  present  day,  then  it  is  '  extinct/  How 
and  when  it  became  so,  we  are  so  far  ignorant. 

It  is  therefore  seen  how  difficult  it  is  to  make  clear 
the  process  of  evolution  for  a  definite  group.  Many 
geologists  entirely  despaired  of  the  possibility  of  so 
exact  a  definition  of  the  ages  of  the  formations  as 
was  needful  to  that  end.  Incomplete,  very  incomplete 
indeed,  must  our  knowledge  ever  be. 

As  has  been  stated,  we  can  grant  that  for  the  great 
geological  formation  system  the  relative  longevity 
has  been  ascertained  with  sufficient  certainty.  Be- 
ginning with  the  youngest,  we  have  arrived  at  the 
following  generally  used  table  of  the  geological 
periods : * 

Formation  Groups.  Formations. 

~       ,.  (Alluvium 

1  Diluvium  (Pleistocene) 

/Pliocene 
~,      .  J  Miocene 

]  Oligocene 

\Eocene 

1  For  more  exact  indications  and  subdivisions  vide  Kayser :  Lehrbuch 
der  Oeolog.  Formationskunde,  p.  7. 


THE  THEOKY  OF  EVOLUTION 

Formation  Groups.  Formations. 


/Chalk  | Upper  Chalk  with  many  grades 

( Lower  Chalk 


Secondary 


Malm 


Jura  |  Dogger 

vLias 

[Keuper 
VTrias  j  Mussel  Chalk      „ 

(New  Eed  Sandstone 

TW<-  a  /-P        \  (Permian  Limestone 
JJyas  (rerm.)  i  ™  -•  T»   i  n      -, 

'  (Old  Eed  Sandstone 

Carboniferous 


Primary     .     .     .   .  _ 

Devonian 

Silurian 
Cambrian 


To  these  are  to  be  added  now  the  pre- Cambrian 
(Algonkium).  Under  these  lie  gneiss  and  mica  slate. 

The  first  fossiliferous  formations  are  the  so-called 
pre-Cambrian.  The  primary  rocks  (gneiss  and  crystal- 
line slate),  upon  which  the  pre-Cambrian  sediments  lie, 
conceal  no  organic  petrifactions  of  any  kind  at  all.1 
It  must  therefore  be  accepted  that,  in  the  seas  in  which 
the  oldest  sediments  were  deposited,  life  really  appeared 
in  the  first  place.  That  must  have  happened  very 
long  ago,  since,  if  we  imagine  all  the  formations  super- 
posed on  each  other,  the  total  would  be  of  a  thickness 
of  about  200  kilometres — about  120  miles. 

1  With  regard  to  the  alleged  fossils  of  the  Primary  rocks  see  Kayser : 
Lefirbucli  der  Geolog.  Formationskunde,  p.  21.  The  freedom  from  fossils  of 
the  Primary  rocks  '  is  only  temporarily  shaken  ' — at  first  by  the  Eozoon 
Canadense,  which  was  recognized  as  serpentine  excrescences.  Since  then 
other  assumed  traces  of  organisms  have  deceptively  appeared,  but  the 
Primary  rocks  must  be  again,  as  previously,  regarded  as  entirely  free  from 
fossils  ;  *  also  the  presence  of  lime  or  graphite  does  not  imply  organic  life, 
since  both  have  been  proved  to  be  able  to  originate  also  on  inorganic  lines.' 


KESULTS  OF  PAL^EONTOLOGICAL  EESEARCH     23 

(1)  First  appearance  of  life  in  the  lowest  (oldest) 
sedimentary  formations. 

The  oldest  well-preserved  fauna  (of  plants  nothing 
has  survived  but  a  few  marine  algae)  is  that  of  the 
Cambrian  system.  It  occurs  in  striking  abundance 
and  extent.  '  The  majority  of  the  important  groups 
of  invertebrate  animals  were  already  clearly  differen- 
tiated/ and  the  Foraminifera,  Sponges,  Corals  (and 
Medusae),  Brachypods,  Snails,  Cephalopods,  and  Arthro- 
pods were  present.  These  groups  were  partially  again 
split  up  into  many  species  and  genera  :  the  Trilobites 
(Crabs)  formed  fifty  genera  with  150  species ;  the 
Echinidee  occur  in  three  types ;  the  Cephalopods,  the 
'  highest  type  of  the  Mollusc  class/  are  already  repre- 
sented (Orthoceratidae).  The  Crabs  proper  (independ- 
ently of  the  Trilobites)  form  two  well-separated  groups 
(Ostracoda  and  Malacostraca).1 

On  the  other  hand  no  remains  of  Vertebrates  have 
yet  been  found. 

In  the  pre-Cambrian  formations,  which  have  nearly 
everywhere  experienced  great  metamorphic  changes, 
fossils  are  found  only  now  and  then.  According  to 
the  latest  investigations  undertaken  by  J.  Walther 3 
on  the  spot  (in  California,  Scotland,  and  Norway,  the 
sites  of  the  most  important  discoveries  in  pre-Cambrian 
strata)  there  have  been  found,  as  the  most  ancient  traces 

1  Deperet-Wegner :    Die  Umbildung  der  Tierwelt,  p.   233.      Kayser : 
Lehrbuch  der  Geolog.  Formationskunde,  p.  75. 

2  Ueber  AlgcmJcische  (=pre-Camb.)  Sedimente,  Naturw.  Rundshau,  1910, 
p.  158. 


24  THE  THEORY  OF  EVOLUTION 

of  life,  worm-tubes,  trilobites,  brachypods,  and  snails 
(among  them  a  genus  which  still  exists — Pleurotomaria 
of  two  species),  these  representing  already  fairly  de- 
veloped organisms.  Other  finds  in  Brittany  are  dubious. 
But  obvious  limbs  of  starfish  (Crinoidse)  occur. 

The  pre-Cambrian  fauna  appears  therefore  to  be  about 
as  perfect  as  that  of  the  Cambrian  formation  itself. 

Conclusions  from  (1) : 

(a)  The  first  organisms  appear  together,  not  succes- 
sively, in  types  or  groups  clearly  separated  from  each  other. 

Most  of  the  invertebrate  classes  are  found. 

Many  forms,  it  is  true,  carry  the  impress  of  simplicity 
('  clumsiness  '  it  might  be  termed),  like  the  Crabs ;  the 
Snails  are  still  small  and  but  slightly  typical ;  the  Cepha- 
lopods  are  only  represented  by  puny  forms  with  a  flattish 
shell x  (in  contrast  to  the  manifold  crooked  and  orna- 
mented shells  of  the  later  representatives  of  this  group). 

(6)  Only  one  group  (Trilobites)  shows  already  a 
very  profuse  branching  into  divergent  differ entiated 
forms.  Fifty  genera  and  about  150  species. 

(c)  Monocellular  organisms  are  preserved — Fora- 
minifera — but  they  by  no  means  form  the  chief 
component  of  the  primary  fauna  (as  the  terrestrial 
evolutionary  hypotheses  demand) ;  (  from  the  beginning 
of  animal  life  we  are  already  infinitely  far  removed  ' 2 
i.e.  the  '  beginning  '  of  life  had  not  been  thus  imagined. 

1  Kayser  :  Lehrbuch  der  Geolog.  Formationskunde,  p.  80. 

2  E.  Koken:  Die  Vorweltundihre  EntwicJdungsgeschichte,  Leipzig,  1893, 
p.  82.     This  remark  of  Koken' s  is  to  be  understood  from  the  standpoint  of 
certain  hypotheses  of  evolution  which  prescribe  a  fauna  of  entirely  different 
character. 


KESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     25 

(d)  As  regards  the  origin  of  the  groups  already 
existent  in  the  Cambrian  and  pre- Cambrian  period 
we  shall  never  know  anything  certain,  not  even  if  other 
organisms  really  preceded  them,  as  is  demanded  as  a 
postulate  by  the  extreme  evolutionary  hypotheses.1 

In  the  meantime  is  the  pre- Cambrian  or  Cambrian 
fauna  to  be  scientifically  regarded  as  the  real  original 
fauna  ?  The  groups  already  existing  show,  in  many 
representatives,  about  the  medium  height  of  organiza- 
tion of  the  animals  of  the  present  day.  Of  a  fauna 
in  its  entirety,  of  a  lower  grade  and  still  older,  there 
have  been  in  any  case  no  remains  discovered  (see  c). 
If  such  really  existed  we  should  hardly  ever  be  likely 
to  learn  something  from  it  (see  d),  since  the  formations 
which  are  older  than  the  pre-Cambrian — nay,  even 
these  themselves  for  the  greater  part — are  throughout 
so  greatly  metamorphosed  that  all  and  any  fossils 
which  they  might  have  contained  would  be  destroyed. 

(2)  The  form  of  animal  life  in  the  post-Cambrian 
formations. 

The  justification  for  uniting  several  sedimentary 
formations  in  a  single  group  (formation,  e.g.  Silurian, 
Devonian,  etc.)  is  found  in  certain  peculiarities  which 
we  see  recur  in  the  history  of  organic  life  in  what 

1  Deperet-Wegner  :  Die  UmUldung  der  Tierwelt,  p.  312.  '  From  these 
facts  should  it  be  concluded  that  we  must  for  ever  desist  from  hoping  to 
solve  a  problem  so  passionately  discussed  as  that  of  the  commencement 
of  life  on  the  earth,  or  at  least  to  be  able  to  follow  it  further  back  ? 
Unhappily  it  must  be  granted  that  that  is  the  most  probable  prospect 
before  us.'  (This  remark  shows  also  that  a  so  highly  developed  fauna  was 
not  anticipated.) 


26  THE  THEORY  OF  EVOLUTION 

might  almost  be  termed  rhythmic  order.  These 
peculiarities  are  the  first  appearance  of  new  and  higher 
types  which  were  previously  absent  (larger  groups, 
e.g.  classes  or  families),  vigorous  development  of  some 
of  the  already- existing  types,  and  the  decay  and  dis- 
appearance of  other  and  previously  very  varied  ones. 

The  Cambrian  or  pre-Cambrian  formations  show 
in  a  general  way  organisms  for  the  first  time ;  they 
are  sharply  defined  according  to  depth.  None  of 
the  classes  of  Invertebrates  which  existed  were  as 
yet  freely  divided  into  genera  and  species,  they  show 
no  specialized  adaptation  to  the  various  environ- 
ments (i.e.  but  few  families,  genera,  and  species)  ;  the 
Trilobites  alone  form  an  exception. 

The  individuals  are  still  small  and  simply  con- 
structed ;  the  Cephalopods,  for  instance,  have  simple 
straight  shells  in  contrast  to  the  highly  complicated, 
curled,  and  ornamented  ones  of  the  Cephalopods  of  later 
formations.1 

All  at  once  there  appear,  in  a  definite  series  of  strata, 
the  first  fishes,  i.e.  the  first  representatives  of  the 
family  of  Vertebrates ;  the  first  land  plants  also  appear.2 
The  Corals,  Starfish,  and  Graptolites  (related  to  the 
Bryozoa,  but  long  extinct),  which  were  very  rare  in  the 
Cambrian  formation,  become  more  numerous. 

The  Trilobites  develop  more  abundantly,  the  more 

1  Good  tabulated  illustrations  (one  short  and  one  in  detail)  of  the 
chief  groups  of  animals  and  plants  from  these  three  points  of  view  are 
given  in  H.  Credner's  Elemente  der  Geologie  (1902),  pp.  363,  365. 

2  We  remark  once  and  for  all  that  '  first  appearance  '  is  intended  only 
to  mean  '  fresh  found.'     Perhaps  the  two  are  synonymous  ;  perhaps  not. 


RESULTS  OF  PAL^EONTOLOGICAL  RESEARCH     27 

perfect  forms  with  well-developed  eyes  and  with  the 
faculty  of  rolling  themselves  tip,  obtain  preponder- 
ance ;  the  Cephalopods,  certainly  only  a  branch  of  the 
Nautiloids,  become  plentiful  and  of  many  types ; 
the  Ammonites  are  almost  entirely  absent — their 
time  has  to  come. 

The  shells  of  the  Orthoceras  forms  are  somewhat 
convoluted. 

The  Crinoids  (rare  in  the  Cambrian  formation) 
become  very  numerous;  to  them  are  added,  but  at 
first  sparsely,  the  two  new  classes  of  Echinidae,  the 
sea  stars,  and  sea  urchin. 

The  Bryozoa  are  also  noticed,  but  they  are  far 
from  having  the  importance  they  later  acquired. 

In  short,  we  understand  why — in  view  of  the  first 
Vertebrates  and  land  plants,  in  view  of  so  many  new 
orders  and  families  appearing  within  classes  already 
existent,  and  in  view  of  the  great  number  of  families, 
genera,  and  species  into  which  other  classes  and 
orders,  as  it  appeared,  simultaneously  and  surprisingly 
quickly  ('  explosively ')  split  themselves  up — a  new 
'  creation/  the  Silurian,  can  be  spoken  of. 

We  cannot  go  through  the  formations  separately, 
but  confine  ourselves  here  once  more  to  the  deter- 
mination of  the  chief  results  which  are  necessary  to 
further  explanations.1 

1  E.  Kayser  (Lehrbuchder  Geolog.  FormationsJcunde),  after  discussing  the 
separate  formations,  gives  a  good  palaeontological  purview,  to  which  the 
reader  is  referred.  K.  von  Zittel's  Handbuch  der  Paldontologie,  Munich  and 
Leipzig,  1876-1893  (5  vols.),goes  more  into  detail.  Regarding  the  history 
of  the  Vertebrates  the  best  information  is  given  by  E.  Frieherr  Stromer  v. 


28  THE  THEORY  OF  EVOLUTION 

On  the  whole  the  higher  classes  of  vertebrates  in 
the  post-Cambrian  formation  follow  the  lower,  and 
often,  within  the  classes,  the  higher  forms  follow  the 
lower.  The  latter  applies  also  in  many  cases  to  the 
Invertebrates. 

The  vertebrate  classes  as  now  represented  are, 
beginning  at  the  lower,  the  Fishes,  Amphibia,  Eeptilia, 
Birds,  and  Mammalia. 

The  Fishes  appear  for  the  first  time  in  the  Silurian 
formation,  and  are  divided  into  three  different  groups  : 
these  are  the  Sharks,  which  rank  as  low  grade  ;  the 
other  groups  were  armoured,  clumsy  forms  which 
subsequently  disappeared.1 

The  Amphibia  appear  in  the  upper  Devonian.2 

The  Reptiles,  certainly  strange-looking  forms,  show 
themselves  for  the  first  time  in  the  upper  Carboniferous 
formation  ('  Sauravus  ').3  In  the  Permian  there  appear 
two  orders  of  Reptilia  which  have  died  out  except  one 
(genus  Hatter ia)  which  now  exists  in  New  Zealand  and 
has  always  been  regarded  as  a  stranger  in  our  animal 
world.  Quite  recently  came  the  discovery  of  three 
great  groups  of  '  well-developed  land  reptiles '  in 
the  Russian  Permian  formation.1* 

Reichenbach's  Lehrbuch  der  Paldontologie  (Naturwissenschaft  und  Technik 
in  Lehre  und  Forschung),  Leipzig -Berlin,  1909,  Part  1.  J.  Bumuller  handles 
the  question  on  briefer  lines  (Die  EntwicJclungstheorie  und  der  Mensch, 
Munich,  1907,  p.  50).  This  excellent  and  inexpensive  work  is  highly 
to  be  commended. 

1  E.  Kayser,  p.  138. 

2  Deperet-Wegner  :  Die  Umbildung  der  Tierwelt,  p.  229. 

3  Ibid. 

4  Ibid.  p.  230. 


RESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     29 

The  forms  which  most  nearly  approach  the  chief 
reptilian  order  of  the  present  day — turtles,  crocodiles, 
and  serpents — appeared  later. 

The  Birds  are  known  to  us  through  the  two  Archae- 
opteryx  from  the  Solnhof  Slate  (upper  Jura).  Remains 
of  birds,  as  generally  of  all  land  animals,  can  naturally 
be  but  seldom  preserved.  The  two  Archseopteryx  tell  us 
practically  nothing  at  all  of  the  history  of  the  Birds. 

The  Mammalia  appear,  as  a  class  regarded  generally, 
for  the  first  time  in  the  upper  Trias l  and  in  forms  which 
nearly  approach  the  lowest  orders  of  the  class  of  Cloaca 
and  Marsupials.3 

The  higher  orders  appear  later,  but  then  certainly 
and  simultaneously  and  partly  in  the  most  differentiated 
forms  such  as  the  whale  (Cetacese)  bats,  and  Probo- 
scidae  (Tertiary  in  the  Eocene  period).3 

Conclusions  from  (2)  :  The  higher  classes  of  the 
Vertebrates  appear  after  the  lower  (Birds  ?) ;  within  the 
classes  also  the  higher  orders  appear  later  than  the  lower. 

Many  groups  (it  might  perhaps  be  said  of  all,  were 
the  evidence  more  perfect)  show  always  at  their  first 
appearance  already  a  division  at  least  into  some  higher 

1  The  Mammalia  were  therefore  older  than  the  Birds,  the  first  remains 
of  which  come  from  the  later  Jura,  if  the  Archseopteryx  may  not  be 
regarded  as  shattered  examples  which  have  reached  us  altogether  by 
chance.     Possibly  the  birds  are  much  older. 

2  Marsupials  and  Cloaca  are  primitive  forms  because,  since  with  them 
the  development  of  the  embryos  is — entirely  with  the  Cloaca,  or  mainly,  as 
with  the  Marsupials — extra-uterine.     With  the  higher  orders  a  placenta  is 
formed,  and  the  development  is  entirely  inter-uterine. 

3  Further  particulars  concerning  the  classes  of  Vertebrates  are  to  be 
found  in  G.  Steinmann's  Die  Geologischen  Grundlagen  der  Abstammungslehre, 
p.  203. 


30  THE  THEORY  OF  EVOLUTION 

systematic  categories.  It  is  often  observed  that  sack 
groups  in  the  following  series  of  strata  '  suddenly ' 
extend  themselves  and  thereby  split  up  into  numerous 
families,  genera,  and  species.  As  a  set-off  other  forms 
often  contemporaneously  die  out. 

§  2.  Inter-relation  between  the  greater  systematic  groups 
(families,  classes,  and  partly  orders}. 

If  therefore  we  concede  that,  on  the  whole,  the 
higher  forms  chronologically  follow  the  lower,  do  they 
originate  therefrom  ? 

(1)  The  Invertebrates  appear  together  in  the 
Cambrian  formation,  but  clearly  separated  into  all 
the  families  and  most  of  the  classes l  which  exist 
at  present  (see  above,  page  23).  Meanwhile  we  are 
absolutely  compelled  to  regard  them  all  as  originally 
separated  groups. 

'  All  the  important  phylae  (families),  sharply  denned, 
reach  back  far  into  the  Cambrian  formation,  and  of 
those  periods  in  which  they  might  have  been  united 
we  have  no  records/  ~ 

We  have  known  for  a  long  time  that  the  majority 
of  the  great  groups  of  invertebrate  animals  are  already 
quite  distinctly  separated  in  the  Cambrian  era.3 

We  cannot  therefore  deduce  as  originating  from 
each  other  the  classes  of  Invertebrates  as  they  have 
been  preserved  to  the  present. 

1  Families,  for   examples,  are   the    Worms,  the  Ccelenterata  (corals, 
bryozoa,  medusae),  in  the  Sea  Urchins  (Echinodermata). 

2  E.  Koken  :  Paldontologie  und  Descendenzlehre,  p.  12. 

3  Deperet-Wegner  :  Die  Umbildung  der  Tierwelt,  p.  233. 


KESULTS  OF  PAL.EONTOLOGICAL  KESEAKCH     31 

(2)  Of  the  Vertebrates,  the  Fishes  (Silurian)  show  no 
connection  with  lower  forms  :  they  appear  as  suddenly 
existent. 

'  We  recognize  the  Fishes  as  the  oldest  Vertebrates, 
which  already  in  the  lower  Silurian  formation  appear 
as  clearly  separated  from  the  Invertebrates/  l  They 
are,  indeed,  not  only  different  from  the  Invertebrates 
from  the  beginning,  but  in  the  group  of  the  primary 
fishes  itself  '.  .  .  there  are  numerous  quite  different 
types  co-existing  but  separate  from  the  beginning/2 
The  same  remark  applies  to  the  first  Amphibia  and 
Kepti ha.3  It  is  true  that  in  the  Permian  system  (in 
the  Carboniferous  there  appear  a  few  representatives) 
a  peculiar  group  of  animals  widely  prevailed — the  so- 
called  Stegocephalse — which  possess  many  characters 
of  the  present  Amphibians  (free  larval  condition  and 
two  occipital  swellings)  and  others  of  the  present 
Keptilia  (scaly  covering)  in  combination.  In  their 
appearance  they  resemble,  for  instance,  salamanders 
(Amphibia)  or  lizards,  crocodiles,  and  snakes  (Eeptilia). 

But,  contemporaneously,  there  already  lived  true 
reptiles  (among  them  Hatteria  up  to  the  present  time) 
and  true  Amphibia  even  previously  (see  p.  28).  The 
Stegocephalae  cannot  therefore  be  regarded  as  the 
common  ancestors  of  the  Reptilia  and  Amphibia. 

With  regard  to  the  origin  of  the  present  reptilian 

1  Steinmann :  Die  Geologischen  Grundlagen  der  Abstammungslehre,  p.  203. 

2  Ibid.  p.  206. 

3  Ibid.     The  origin  of  the  Quadrupeds  is  still  not  cleared  up.— Koken  : 
Paldontologie  und  Descendenzlehre,  p.  241. 


32  THE  THEORY  OF  EVOLUTION 

orders  (Turtles,  Crocodiles,  Snakes,  and  Lizards)  nothing 
is  known.1 

The  first  birds,  Archseopteryx,  have  toothed  beaks, 
the  vertebrae  of  the  long  tail  remain  separated,  the 
free  digits  of  the  front  limb  (=  hand  or  wing)  carry 
claws.  These  are  characters  which  occur  now  in 
reptiles.  This  bird  has,  furthermore,  many  other 
peculiarities  confined  to  itself. 

From  this  it  was  concluded  that  birds  were  descended 
from  reptiles.  But  all  attempts  failed  to  trace  a  con- 
nection with  any  particular  reptile.2  The  nearest  birds 
(Cretacean)  can  by  their  habit  be  assigned  to  quite 
definite  bird  families — Laornis,  for  example,  to  the 
Geese — so  that  Steinmann  can  say  '  each  of  the  three 
well-recognized  types  of  Cretaceous  birds  represents  a 
separate  ancestry. ' 3 

The  Mammalia  show  from  the  beginning  '  two 
groups  of  lower  mammalia  quite  clearly  differentiated/  •* 
Then  they  almost  disappear  during  the  immense  Mesozoic 
period  (=  Secondary  formation  group),  and  appear 
again  at  the  commencement  of  the  Tertiary  (Eocene) 

1  J.  Bumiiller :  Die  EntwicTdungslJieorie  und  der  Mensch,  p.  23  (according 
to  Zittel's  investigations). 

2  Steinmann :  Die  Geologischen  Grundlagen  der  Abstammung&lelire,  p.  222  : 
'  From  the  older  strata  of  the  Jura  and  from  the  Trias  (which  come  next  into 
consideration)  we  know  practically  nothing  of  small,  long-legged  reptiles 
of  such  a  habit  as  the  Archeeopteryx  demands  as  ancestor.'     Deperet- 
\Vegner  :    Die   Umbildung  der  Tierwelt,   p.   231  :   '  The  Archseopteryx  is, 
however,  a  true  bird  in  its  entire  construction,  and  possesses  beyond  doubt 
a  long  line  of  ancestors  which  at  present  eludes  our  knowledge.' 

3  Steinmann :     Die    Geologischen   Grundlagen    der  Abstammungslehre, 
p.  225. 

4  Deperet-Wegner  :  Die  Umbildung  der  Tierwdt,  p.  281. 


RESULTS  OF  PAL^EONTOLOGlCAL  RESEARCH     S3 

period  '  almost  as  fully  typified  and  as  sharply 
defined  as  to-day,  particularly  also  such  as  were  of 
unusual  size  or  of  peculiar  travelling  powers  or  habits 
of  life,  such  as  Cetacese  (whales)  Sirens  (sea-cows) 
Bats,  etc/1 

Summarizing,  J.  Bumuller  says  3  e.  .  .  We  have  there- 
fore the  remarkable  fact  that  the  placental  Mammalia, 
which  appeared  first  in  the  Tertiary  period  (see  remark 
above,  p.  29),  is  already  split  into  all  the  ten  orders  in 
the  oldest  section  of  that  period,  viz.  the  Eocene.  .  .  / 
Where  are  the  predecessors  of  these  orders  ?  Where  are 
the  transitional  forms  between  them  and  the  Marsupials 
which  were  there  already  in  the  Trias  ? 

Deduction  from  §  2  :  Of  a  process  of  separation 
of  the  families  and  classes  of  the  Invertebrates  from 
each  other,  the  higher  from  the  lower,  we  know 
nothing  since  they  appear  contemporaneously  as 
sharply  separated  in  the  Cambrian  formation. 

That  the  higher  classes,  and  even  many  orders  of 
the  Vertebrates,  have  been  evolved  from  the  lower  ones 
is,  according  to  the  actual  results  of  investigation,  in 
no  single  case  other  than  probable.  A  single  apparent 
exception  here  is  that  of  the  Birds.  Archaeopteryx 
was  obviously  a  bird  :  the  entire  construction  of  the 
skeleton,  the  so  characteristic  form  of  the  front  and 
rear  limbs  (wings  and  legs),  the  possession  of  feathers, 
of  which  no  reptile  shows  the  slightest  trace,  separates 

1  Steinmann :    Die    Geologischen    Grundlagen   der    Abstammungslehre, 
p.  233. 

2  J.  Bumuller  :  Die  Entiuicklungstheorie  und  der  Mensch,  p.  76. 


34  THE  THEOKY  OF  EVOLUTION 

it  entirely  from  all  other  classes.  That  the  beak  con- 
tained teeth  while  the  present  birds  no  longer  possess 
them,  that  the  caudal  vertebrae  had  not  yet  become 
united  as  is  now  the  case,  shows  that  it  was  a  different 
bird  from  the  present  ones,  but  otherwise  demonstrates 
nothing.  We  are,  however,  accustomed  to  find  in  the 
first  representatives  of  any  type  divergent  and  (by  com- 
parison with  the  present  ones)  curious  characteristics. 

It  must  therefore  be  assumed  that  the  Birds  bore 
teeth  for  a  long  period  and  only  gradually  lost  them. 
In  that  case  we  should  have  here  a  so-called  apparent 
regression  (see  p.  44). 

§  3.  Some  palceontological  'laws'  according  to  which 
the  transformation  proceeded  within  defined 
(narrower)  groups  (families,  genera).1 

(1)  The  law  of  increase  of  size. 

In  the  previous  matter  we  have  repeatedly  called 
attention  to  the  fact  that  the  first  representatives 
of  a  newly  appearing  group  are  often  small  and 
insignificant  individuals  compared  with  the  later  and 
sometimes  gigantic  forms  within  the  same  group.  This 
is  observed  '  almost  invariably  in  all  classes  of  the  animal 
world,  but  we  find  more  numerous  and  clearer  applica- 
tions of  the  law  in  the  group  of  Vertebrates  than  in 
that  of  the  Invertebrates/  By  careful  investigation 
Neumayr,  Waagen,  Mojsisovics,  and  Hyatt  have  deter- 

1  We  rely  in  this  section  particularly  upon  Deperet-Wegner's  Die 
Umbildung  der  Tierwdt,  chaps,  ix.  and  x.,  where  the  whole  literature  of  the 
subject  is  dealt  with. 


EESULTS  OF  PAL^EONTOLOGICAL  RESEARCH     35 

mined  such  evolutionary  series l  as,  for  instance,  with 
Foraminifera,  Sea  Urchins,  Brachiopoda,  Ammonites, 
Nautilus  among  the  Invertebrates,  many  fish  groups 
(shark,  lungfish),  with  Amphibia,  Reptilia,  and,  before 
all,  also  for  groups  of  Mammalia.  '  Among  the  Mam- 
malia the  law  of  increase  of  size  is  demonstrated  with 
the  utmost  possible  clearness,  so  that  for  the  modern 
palaeontologist  it  may  be  used  as  a  veritable  touch- 
stone in  connection  with  the  reconstruction  of  genea- 
logical trees/  In  many  cases  the  entire  '  evolution ' 
of  the  offspring  is  confined  to  increase  in  size  :  the 
organic  characters  remain  almost  unchanged.2  The 
'  law '  is,  however,  not  general ;  for  instance,  it  does 
not  apply  at  all  to  insects  (see  p.  38). 

(2)  The  law  of  specialization  and  differentiation 
within  more  defined  (narrower)  groups. 

We  have  already  several  times  stated  that  the 
representatives  of  an  organic  class  on  its  first  appear- 
ance show  simple  forms  which  are  not  yet  '  specialized/ 
Frequently  such  groups  split  up  later  into  numerous 
new  forms,  species,  genera,  and  families.  It  has  now 
been  observed  that  this  rich  development  arises  through 
the  original  individuals  changing  in  quite  definite 
directions  :  for  instance,  in  the  Cephalopods  the  shell 

1  Deperet-Wegner  :  Die  Umbildung  der  Tierwelt,  p.  181. 

2  A  classic  example  is  Brachyodus  (Deperet-Wegner :  Die  Umbildung 
der  Tierwelt,  p.  185),  which  is  increased  from  the  size  of  a  hare  to  that  of 
a  rhinoceros,  and  yet  it  retains  the  generic  characters  perfectly  and  only 
forms  another  'species'  than  its  dwarf  ancestors.     Also  in  the  hypo- 
thetical evolutional  history  of  the  Horse,  the  increase  of  size  plays  an 
important  role  ;  it  is  true  that  in  this  case  it  is  accompanied  by  other 
important  modifications. 

D2 


36  THE  THEORY  OF  EVOLUTION 

tends  to  become  more  and  more  convoluted,  more  and 
more  decorated  with  lines  and  excrescences,  or  some 
definite  organ  is  added  and  thereby  indirectly  the 
entire  organism  becomes  more  and  more  specialized 
for  a  definite  function  (mode  of  progression,  transfor- 
mation of  the  limbs  for  swimming,  flying,  running, 
digging,  etc.),  and  as  this  proceeds  always  in  the  same 
direction  it  becomes  more  and  more  adapted  to  the 
particular  function  concerned.  With  these  phenomena 
is  associated  the  well-known  example  of  the  so-called 
horse-foot  series,  which  demonstrates  how,  from  a 
normal  five-toed  foot,  the  one-toed  foot  of  the  present 
horse  has  been  quite  gradually  evolved,  as  a  constantly 
one-sided,  and  therefore,  in  a  certain  sense,  a  more  and 
more  perfect,  adaptation  for  speedy  running.  With 
it  is  furthermore  associated  the  evolution  of  the  paddle 
hand  of  the  Sirens  (sea-cows),  the  evolution  of  defensive 
and  gripping  weapons — for  instance,  the  horns  of  the 
stag  which  from  small  beginnings  arrived  at  colossal 
dimensions  in  the  extinct  gigantic  deer ;  also  the  tusks 
of  the  Proboscidse,  etc.1 

'  Specialization  '  signifies,  therefore,  the  development 
in  one  direction  of  an  organ  or  of  the  entire  organism. 
What  causes  are  effective  are  not  always  demonstrable  ; 
probably  the  necessity  of  purposeful  adaptation  to 
changed  environments  was  the  reason. 

'  Differentiation  '  is  the  development  of  numerous 
variations  of  one  and  the  same  fundamental  type  by 
specialization  of  separate  individuals  in  different  direc- 

1  Deperet-Wcgner  :  Die  Umbildung  der  Tierwelt,  chap.  xx. 


RESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     37 

tions.  As  fundamental  types  we  regard  those  of  the 
first  individuals  which  have  become  known  to  us.  That 
is  perfectly  correct  if  at  least  the  first  representatives 
are  few  and  all  similar  as  between  themselves,  and 
if  it  can  be  accepted  that  precisely  those  individuals 
formed,  in  fact,  the  starting-point  of  later  forms  (species 
and  genera).  In  that  case  it  is  clear  that  one  type, 
originally  confined  to  one  or  a  few  species,  becomes 
varied  or  differentiated. 

With  the  numerical  increase  of  the  individuals  both 
animals  and  plants  naturally  incur  the  necessity  of 
dividing  their  resorts  or  habitats,  they  occupy  different 
elevations  in  valleys  or  on  the  mountains,  deeper  or 
shallower  water,  and  more  humid  or  drier  climates,  etc. 
This  gives  the  impulse  to  varied  specialization.  The 
type  itself  becomes  varied  by  the  varied  specialization 
of  the  separated  individuals. 

The  phylogeny  of  the  Insects  may  be  studied  more 
in  detail  to  elucidate  the  above.  For  this  group  we 
possess  A.  Handlirsch/s  great  work, '  Die  f ossilen  Insecten 
und  die  Phylogenie  der  rezenten  Formen/  l  a  compre- 
hensive presentation  and  consideration  of  the  whole 
of  the  discoveries  so  far  made. 

The  oldest  insects,  the  Palaeodictyoptera  (Fig.  5), 
appear  in  the  lower  strata  of  the  very  productive 
Carboniferous  system.  They  were  of  considerable  size, 
many  of  them  as  long  as  the  hand  or  even  the  arm, 
with  six  legs  and  four  or  six  wings.  The  vein  system 

1  Vol.  II,  Leipzig,  1906-1908.      An  exposition  by  Handlirsch  himself 
appeared  in  Die  Umschau,  1909,  p.  588. 


38 


THE  THEORY  OF  EVOLUTION 


of  the  wings  was  well  developed ;  the  antennae  consisted 
of  numerous  segments;  the  rear  segments  of  the  body 
frequently  bore  gill-like  appendages. 

By  the  appearance  of  their  masticating  and  well- 
developed  jaws  they  were  carnivorous.  Their  larvae 
lived  probably  in  water  like  the  present  Ephemeridae. 
The  body  was  equally  segmented  (homonomous). 

The  whole  of  the  primary  insects  form  together  the 

one  order  of  Palaeo- 

i  / 

dictyoptera,  but  this 
consisted  of  twenty-two 
families  and  115  species. 
The  numerous  orders 
of  the  insects  of  the 
present  day  are  still 
absent.  In  the  upper 
strata  of  the  Palaeozoic 
period  insects  appear 
which  '  undoubtedly 
present  a  definite  ten- 
dency towards  the  modern  insect  orders/  l  Handlirsch 
considers  them  as  '  transitional  groups  between  the 
primary  groups  and  those  to-day  existent,  the  Ortho- 
ptera,  Woodlice,  Dragon-flies,  Ephemeridae,  Hemiptera, 
etc/  In  the  old  terrestrial  formations,  however,  we 
find  already  true  Woodlice,  Ephemeridae,  and  Locusts : 
'  the  Palaeozoic  fauna  is  therefore  totally  different 
from  the  modern  and  much  more  uniform  ' 2  (Fig.  6). 


FIG.  5. — RECONSTRUCTION  OF  THE  PRIMARY 
INSECT  (reduced).     (After  Handlirsch.) 


1  Die  Umschau,  p.  589. 


Ibid. 


RESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     39 


Our  illustration  shows  such  a  transitional  group  from 
the  Palaeozoic  system  which  Handlirsch  regards  as 
the  ancestral  form  of  the  Scorpion  flies,  Phryganidae, 
Flies,  and  Butterflies. 

In  the  Mesozoic  system  the  primary  form  is  no 
longer  found  and  the 
transitional  forms  are 
scarcer.  '  Nearly  all  the 
insects  found  in  these 
formations  can  be  allo- 
cated without  difficulty 
to  the  now  existent 
orders,  although  they 
differ  sufficiently  from 
many  of  the  present  forms 
to  be  considered  separate 
families  or  at  least  genera. ' 

There  appear  true 
Locusts,  Grasshoppers, 
Stick  Insects,  Beetles, 
Phryganidee,  Dragon- 
flies,  Hemiptera,  Butter- 
flies, Bugs,  etc.,  so  that  at  the  end  of  the  Jura 
period  (Figs.  7-9)  all  the  chief  groups  of  the  insect 
world  are  existent  with  the  exception  of  the  Earwigs, 
Termites,  Woodlice,  Field-cricket,  and  the  true  Lice 
(infesting  warm-blooded  animals),  Fur-eaters  and 
Fleas  (Parasites).  Within  the  orders,  however,  there 
are  still  lacking  many  now  widely  extended  families, 
such  as  Wasps,  Ants,  Bees,  true  Flies,  Gall-wasps,  etc. 


FlG.    6. — A     TRANSITIONAL     FORM     FROM 

THE  CARBONIFEROUS  SYSTEM.     (After 
Handlirsch.) 


40  THE  THEORY  OF  EVOLUTION 

The  numerical  relations  differ  also  from  those  of 
to-day. 

That  which  is  lacking  in  the  Jura  '  we  find  already 
richly  represented  in  the  Tertiary  deposits.  All  fami- 
lies now  agree,  as  do  very  many  genera  and  even  several 
species,  with  those  now  existent,  so  that  the  difference 
consists  now  almost  entirely  in  the  numerical  relations 
and  in  the  geographical  distribution/  l 

According  to  the  above  the  whole  of  the  present 


FIG.  7. — BEETLE  FIG.  8.  —  PRIMARY   WOOD  FIG.  9. — DRAGON-FLY 

(Jura).  WASP  (Jura  Hymenoptera).  (Jura). 

FIGS.  7-9.     (After  Handlirsch.} 

insect  orders  with  their  subdivisions  have  arisen  by 
differentiation  of  one  original  type.  This  occurred 
through  changes  in  the  originally  similarly  segmented 
body — for  instance,  in  the  Beetles  and  Hymenoptera, 
into  three  clearly  divided  main  sections  :  head,  breast, 
and  rear  segments.  Other  recent  offshoots,  like  the 
Termites,  show  a  still  more  uniform  segmentation  of 
the  whole  body.  In  the  Thysanura  this  is  complete. 
The  formation  of  the  antennae,  also  the  number  of 
tarsi  and  the  venation  of  the  wings  afford  opportunities 

1  Die,  Umschau,  p.  590. 


KESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     41 

enough  for  specialization  and  particularly  also  the 
formation  of  the  jaws,  which  are  already  differentiated 
for  masticating,  stinging,  sucking,  etc. 

In  many  cases  the  specialization  was  associated 
with  regression,  with  reduction  of  the  number  of  wings 
and  segments. 

As  an  external  impulse  to  variation  Handlirsch 
cites  the  Permian  glacial  epoch  which,  particularly,  as 
a  result  of  the  general  cooling,  may  have  caused  the 
transition  of  the  larval  forms  into  perfectly  metamor- 
phosed ones  as  '  being  generally  better  fitted  for  cold 
seasons/  For  the  late  appearance  (and  origin)  of  the 
Wasps,  Ants,  Bees,  and  Gall-flies,  Handlirsch  considers 
that  in  the  appearance  and  rich  development  of  the 
flowering  plants,  a  sufficient  reason  is  to  be  found. 

Wasmann l  expresses  his  opinion  regarding  the 
history  of  the  origin  of  insects,  as  Handlirsch  presents 
it,  as  follows  :  '  In  the  hypothetical  history  of  insect 
origin  certainly  a  manifold  differentiation  and  specializa- 
tion of  the  insect  type  has  taken  place,  which  was 
connected,  partly  with  an  increased  development  of 
certain  characters,  and  partly  with  a  reduction  in  others. 
Of  an  enhancing  of  the  entire  organic  type  naught 
can  be  said.  ...  A  wingless  worker  ant  can  by  no 
means  be  considered  as  "  a  more  perfect  insect  "  than 
a  six-winged  Pabeodictyopteron  was.  The  primary 
insects  and  those  of  their  present  descendants  which, 
like  the  Ephemeridse,  have  retained  many  of  the 

1  Die  progressive  Artbildung  und  die  Dinarda-Formen  in  Natur  und 
Offenb.,  1909,  no,  6,  p.  333. 


42  THE  THEORY  OF  EVOLUTION 

original  characters,  may  well  be  considered  as  the  most 
primitive  insects,  but  not  as  the  lowest/ 

(3)  The  law  of  the  limitation  of  such  specializations 
in  one  direction — Explanation  of  the  extinction 
of  such  forms. 

(a)  The    almost    sudden    disappearance    of    many 
multifarious  groups  has  long  presented  a  particularly 
attractive    problem.     In    the    Primary    period    there 
appeared,    for    example,    Trilobites    in    the    Cambrian 
system,  they  passed  their  prime  in  the  Silurian  and 
Devonian,   and  entirely   disappeared  in   the   Permian. 
The   same   thing  is   observed   in   the    Primary  epoch 
with  the    Graptolites,    Cystoidse    and    Blastoidse    (sea 
urchins),  with  the  Tetracorals  and  Euryptidae  (gigantic 
crustaceans). 

In  the  Secondary  period  there  may  be  similarly 
observed  the  appearance  and  disappearance  of  the 
Belemnites  (Thunderbolts),  Hippurites,  and  the  gigantic 
Saurians  (Ichthyosaurus,  Plesiosaurus,  and  Pterosaurus). 

In  the  Tertiary  period  occurs  the  appearance  and 
entire  extinction  of  many  large  groups  of  Mammalia. 

(b)  It   has   been  endeavoured  to  account    for  this 
enigmatical  disappearance  of  entire  classes  and  orders 
of  animals  by  catastrophes  (Cuvier),  or  also  by  epidemics 
and  starvation  (Neumayer,  Quenstedt). 

But  the  two  '  laws  '  already  discussed  afford  quite 
another  explanation. 

It  had  always  been  noted  that  '  the  species  of  a 
group  find  themselves  on  the  eve  of  disappearance 


RESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     43 

precisely  when  they  have  attained  the  maximum  of 
prosperity,  either  with  regard  to  the  dimensions  of 
their  bodies  or  in  the  perfection  of  their  weapons  of 
attack  and  defence/  l 

In  the  end,  however,  horns  of  two  metres  in 
breadth,  as  were  borne  by  the  gigantic  deer,  must  be- 
come directly  detrimental ;  reduction  of  a  specialization 
carried  so  far  appears,  however,  to  be  impossible  (law 
of  the  irreversibility  of  evolution).  The  increase  in 
size  has  also  its  limits  ;  if  overstepped  the  size  leads 
to  clumsiness  and  unwieldiness.  If  the  environment 
then  be  altered,  such  forms,  so  peculiarly  modified  in 
the  one  suitable  direction,  are  doomed  to  extinction.2 

Such  environmental  changes  on  a  large  scale  certainly 
occurred.  We  may  consider  only  the  various  mighty 
ice  invasions  which  repeatedly  took  place  :  the  first 
certainly  occurred  already  in  the  pre-Cambrian  epoch,3 
another  in  the  Permian/  and  the  last  great  one  was 
that  of  the  Diluvium.  We  may  further  consider  the 
frequent  incursions  of  the  ocean,  and  the  climatal 
oscillations,  which  resulted  in  our  finding  in  one  and 
the  same  region  the  remains  of  tropical  or  sub-tropical 

1  Deperet-Wegner :  Die  Umbildung  der  Tier  welt,  p.  219. 

2  Recently  the  palaeontologist  R.  Homer  has  exhaustively  discussed 
the  question  of  Extinction  in  his  work   Das  Austerben  der  Arten  und 
Gattungen  sowie  der  grosseren  Gruppen  der  Tier-  und  Pflanzenwelt,  Graz, 
1911.     In  essentials  he  agrees  with  Deperet's  views. 

3  J.  Walther:  Ueber  algonkische  Sedimente,  in  Naturw.  Rundschau,  1910, 
p.  158.     E.  Kayser :  Lehrbuch  der  Geolog.  Formationskunde,  p.  50,  Supple- 
ment.   (Clear  traces  are  found  of  same  in  N.  America,  Norway,  and  China.) 

4  E.  Philippi :  Ueber  die  Permische  Eiszeit,  u.  Zentralblatt  fur  Mineralogie, 
Geologie,  und  Paldantologie,  1908,  p.  353.    The  author  regards  it  as  *  proved.' 


44  THE  THEOKY  OF  EVOLUTION 

animals   and  those   of    the  present   Siberian   or  high 
alpine  fauna  superposed. 

(4)  The  phenomena  of  regression  and  of  convergence 
(Law  of  Convergence). 

(a)  Regressive  Evidence. — Many  animals  experience 
during  their  individual  lives,  under  the  influence  of 
particular  conditions  (parasitism  for  example,  or  transfer 
to  an  established  mode  of  life),  a  clear  depreciation  of 
many  organs  through  regression  and  reversion.  The 
digestive  apparatus  can  be  entirely  transformed — for 
instance,  in  the  female  of  many  parasitic  crabs  (Ler- 
naiden),1  as  also  that  of  locomotion,  which  in  both  cases 
are  no  longer  purposeful  for  movement  from  place  to 
place  and  therefore  disappear  (Lernaiden  for  instance) 
or  serve  other  purposes  (direction  of  nutriment  towards 
the  mouth)  as  will  the  species  of  Lepas,  the  so-called 
'  Duck  Mussels  '  in  the  Crab  group  of  Centipedise. 

Palaeontology,  in  the  opinion  of  serious  investigators, 
has  now  afforded  some  evidence  of  the  way  in  which, 
in  the  course  of  geological  time,  a  reversion  of  some 
sections  of  organisms  gradually  occurred.  Thus  the 
presumed  parents  of  the  horse  of  to-day  possessed 
fully-developed  lateral  toes  which  now  appear  only 
as  '  sesamoid  bones 9  and  are  hidden  beneath  the 
skin.  It  is  furthermore  accepted  that  the  Birds,  whose 
oldest  representatives  in  the  Jura  and  the  Chalk  forma- 
tions all  possessed  teeth,  lost  them  gradually.  In 
young  parrots  and  in  the  embryos  of  other  birds  of 

1  R.  Hertwig  :  LcJirbuch  der  Zoologie,  Jena,  1907,  p.  382. 


RESULTS  OF  PALJEONTOLOGICAL  RESEARCH     45 

to-day  there  is  still  discoverable  traces  of  tooth-bearing 
jaws.1  Furthermore  the  so-called  medial  eye  on  the 
head,  which  was  well  developed  in  many  palseonto- 
logical  reptiles,  has  retrograded  and  been  lost.  In 
Hatteria — this  relic  of  a  long-vanished  world — the 
medial  eye  is  still  existent  but  is  hidden  under  an 
opaque  skin.2 

These  evidences  of  retrogression,  which  appear  in 
the  forms  of  the  present  day  as  so-called  (  rudimentary 
organs/  have,  in  the  opinion  of  palaeontologists,  con- 
tributed much  to  the  transformation  of  the  animal 
world.  The  alteration  frequently  extends  only  to 
a  system  of  organs  which,  by  reason  of  a  transfer  to 
a  new  mode  of  life,  have  become  superfluous,  and 
frequently  only  to  a  part  of  same  ;  hence  in  the  opinion 
of  many  investigators  the  so-called  fins  of  the  whale  are 
a  positive  adaptation  of  the  front  limbs  to  swimming, 
and  thereby  no  retrogression  but  a  ( specialization/ 
while  the  hinder  parts  (legs  and  pelvis)  have  dwindled 
and  now  only  remain  as  an  insignificant  bony  rudiment 
buried  within  the  fat  of  the  whale. 

This,  however,  brings  us  already  to  the  so-called 
convergence  evidence. 

(6)  Evidence  of  Convergence.— It  is  frequently 
observed  that  animals  which,  systematically,  stand 
far  apart,  exhibit  changes  in  the  same  direction  and 
develop  these  further,  so  that  by  their  further  evolu- 
tion they  approach  each  other  nearer  than  they  were 

1  Deperet-Wegner  :  Die  Umbildung  der  Tierwelt,  p.  202. 

2  Ibid. 


46  THE  THEORY  OF  EVOLUTION 

before :  they  converge  towards  each  other.  Thus, 
for  instance,  many  mussels  which  by  their  construc- 
tion belong  to  various  species  and  genera,  commence 
at  the  same  time  or  successively  to  alter  their  shells 
in  the  same  direction.  Since  now  it  is  the  shells  alone 
which  are  preserved,  in  those  cases  where  the  remainder 
of  the  varied  organism  has  left  no  trace  we  can  no 
longer  know  with  what  species  or  genera  we  have  to 
deal. 

Yet  the  similarity  thus  engendered  is  mostly  only 
superficial  since  it  extends  almost  always  only  to  the 
shells,  scales,  and  epidermal  plates,  as  we  see  in  the 
Molluscs,  Fishes,  and  Eeptiles ;  or,  since  only  some 
of  the  organs — for  instance,  those  of  locomotion — are 
similarly  formed,  the  peculiarities  of  the  whole 
organization  are  never  perfectly  eliminated.  It  is, 
therefore,  by  convergence  that  we  explain  how,  within 
quite  different  groups  of  mammalia,  a  most  deceptive 
similarity  of  the  jaw  construction  is  observed  ;  in  this 
case  this  is  undoubtedly  caused  by  habituation  to  the 
same  kind  of  nutrition.1 

By  convergence  is  explained  also  the  entire  '  fish 
resemblance  '  of  the  Whales,  which,  when  habituating 
themselves  to  life  in  the  water,  were  guided,  so  to 
speak,  by  the  water  inhabitants  par  excellence,  the 
Fishes — that  is,  they  changed  their  forelimbs  (arms)  into 

1  If  only  separated  plates  (shields)  or  separate  teeth  are  found  then  we 
cannot  tell  to  which  animal  group  they  should  be  assigned.  Hence  recently 
a  polygonal  epidermal  plate  was  ascribed  by  Filhol  to  an  extinct  armadillo 
(Mammalia),  but  later  an  almost  exact  replica  was  found,  but  this  time  on 
the  head  of  a  reptile  (Placosaurus). —  Umbildung  der  TierwelL  p.  208. 


EESULTS  OF  PAL^EONTOLOGICAL  RESEAKCH     47 

fins  (paddles)  and  their  hind  limbs  became  entirely 
useless.  The  tail  became  likewise  transformed  into 
a  rudder,  which,  indeed,  is  the  case  with  the  Fishes,  etc. 
Yet  mammals  they  remain  all  the  same,  since  the 
mammalian  nature  is  not  in  itself  contradictory  to 
an  aqueous  existence  ;  but  everything  that  was  specially 
adapted  for  a  land  life  must  be  transformed  to  fit 
the  new  water  one  and  that  only. 

Hence  they  converged  ever  more  and  more  in  ex- 
ternal features  towards  the  Fishes,  with  whom  otherwise 
they  are  not  at  all  related. 

Naturally  such  evidence  of  convergence  must  be 
established  or  rendered  probable  by  exact  comparison 
of  changes  in  both  the  converging  groups.  Of  the 
Whales  there  are  lacking  entirely  fossil  remains  of  any 
kind  whatever.1 

In  point  of  fact  so  far  no  evidence  of  convergence 
has  been  palaeontologically  determined,  by  which 
even  only  the  original  generic  characters  have  been 
perfectly  eliminated.2  '  On  the  whole  I  think/  says 
Deperet,  '  that  the  evidences  of  convergence  which 
were  asserted  in  connection  with  nearly  all  animal 
groups  were  greatly  overestimated.  In  the  majority 

1  Steinmann  (Die  Geologischen  Grundlagen,  etc.,  p.  235)  will  not  accept 
the  idea  of  descent  of  the  Whales  from   quadrupedal  ancestors.     He 
endeavours  to  explain  their  descent  from  definite  groups  of  the  great 
Mesozoic  Saurians.     There  is  much  to  be  said  for  his  opinion,  but  '  very 
convincing '  it  is  not. 

2  Deperet- Wegner :  Die    Umbildung   der  Tierwelt,  p.  205.     Professor 
Fleischmann   (Die  Darivinische   Theorie,   Leipzig,    1903,    p.  263)  writes, 
regarding  the  origin  of  the  whale,  a  veritable  satire,  most  delightful  to  read, 
but  which  avoids  all  explanation. 


48  THE  THEORY  OF  EVOLUTION 

of  cases  the  resemblances  of  this  kind  are  very  super- 
ficial and  can  be  easily  explained  by  the  process  of 
adaptation  to  functions  common  to  both/  l 

Conclusions  derived  from  palaeontology  : 

We  have  seen  that  the  changes  or  transformations 
which  are  experienced  by  the  organisms  never  exceed 
the  limits  of  the  families  and  classes,  nor  generally 
those  of  the  orders  (§  2). 

According,  therefore,  to  the  present  position  of  science, 
there  is  no  unlimited  transformation  in  the  animal  world. 

It  is  true  that  with  the  Vertebrates,  on  the  whole, 
the  higher  classes  appear  after  the  lower  (§  1).  To 
show  how  both,  viz.  the  appearance  after  each  other 
and  yet  no  derivation  from  each  other,  can  be  brought 
into  accord  is  reserved  for  the  evolutionary  hypotheses. 
We  will  express  a  supposition  relative  thereto  later  on. 

In  §  3  we  saw  in  what  way  originally  like  or  similar 
forms  could  arrive  at  varied  appearances.  This  happens 
through  an  ever-increased  adaptation  to  quite  definite 
modes  of  life  by  which,  in  some  cases,  the  whole  organ- 
ism is  transformed — generally,  however,  only  separate 
organs.  There  is  often  observed  also  an  increase  of 
size,  in  conformity  with  a  recognized  law,  mostly  in 
conjunction  with  other  changes,  but  in  a  few  there 
is  increase  of  size  alone. 

It  may  also  happen  that  animals  originally  widely 
separated  in  kind  become  more  similar  by  variation 
in  the  same  direction. 

1  Deperet-Wegner :   Die,  Umbildung  der  Tierwell,  p.  213. 


RESULTS  OF  PAL.EONTOLOGICAL  RESEARCH    49 

It  therefore  happens  that  the  appearance  of  the 
organisms  is  constantly  changing,  and  forms  appear 
which  are  new  and  specialized,  i.e.  adapted  to  quite 
definite  modes  of  existence,  nutrition,  habitats,  etc. 
But  in  no  case  does  the  entire  change,  which  the  organ- 
isms finally  show  in  comparison  with  the  original  form, 
go  so  far  that  offspring  and  ancestors  can  no  longer 
be  united  within  the  same  systematic  class.  Generally 
the  totality  of  the  descendants  and  ancestors,  despite 
all  '  evolution/  still  form  the  same  order,  the  same 
family,  and  sometimes  even  the  same  genus.  '  Genea- 
logical trees '  or  pedigrees  which  ignore  all  systematic 
classification  are  simply  illusory. 

The  '  evolutionary  series  '  (pedigrees)  of  some  organ- 
isms, the  course  of  which  may  be  followed  more  or  less 
without  hiatus,  never  present  such  considerable  devia- 
tions from  each  other  that  the  new  forms  (species  and 
genera)  must  be  arranged  l  in  separate  natural  families/  x 

B. — RESULTS  OF  PAL^OBOTANY   (EVOLUTION  OF  THE 
PLANT  WORLD). 

With  the  history  of  the  evolution  of  the  plant  world 
we  are  less  acquainted  than  with  that  of  the  animals. 
This  is  due  to  various  causes. 

In  order  that  organisms  may  be  preserved  in  a 
fossil  form  they  must  be  withdrawn  from  the  corrod- 
ing influence  of  the  atmosphere,  particularly  the  free 
access  of  oxygen.  This  happens  generally,  and  is  best 
effected,  by  deposition  of  mud,  sand,  or  even  of  other 

1  Daperet-Wegner  :  Die  Umbildung  der  TierweU,  p.  250. 


50 


THE  THEORY  OF  EVOLUTION 


organisms  under  water.     For  this  reason  land  dwellers 

o 

rarely  become  fossilized. 

For  the  investigation  of  the  old-world  fauna  this 
circumstance  is  less  serious  than  for  the  flora,  since 
the  greater  number  of  the  animals  are  and  were 
inhabitants  of  the  water  and  par- 
ticularly of  the  ocean.  But  of  the 
higher  plants l  which  inhabited  the 
sea  we  know  nothing. 

Hence  it  happens  that  formations 
which  are  exclusively  marine  and, 
particularly  for  our  present  inquiry, 
very  important  stratifications — the 
pre- Cambrian,  Cambrian,  Silurian, 
Mussel  Chalk,  and  others — only  now 
and  then  offer  examples  of  sub- 
merged land  plants.  With  regard 
to  the  flora  we  gather  exact  data 
only  from  those  periods  and  regions 
where  extensive  areas  of  land  were 
marshy  or,  owing  to  great  aerial 
humidity,  were  covered  with  forests.  Only  under  such 
circumstances  were  the  conditions  existent  for  such 
processes  as  led  to  the  formation  of  the  coal  seams,  in 
which  we  find  entire  generations  of  successive  growths,3 
and  these  in  the  best  condition.  It  must  also  be 
considered  that  none  of  the  primeval  plants  have 

'  Higher  plants '  we  only  accept  temporarily  in  the  sense  of  their 
higher  systematic  position,  as  they  are  recognized  generally  by  botanists. 

2  H.   Potonie:   Die  Entstehung  der  Steinkohle  und  der  Kaustobiolithe 
uberhaupt,  Berlin,  1910. 


FIG.  10. — SECTIONS   OF 

BEECH. 

a,  with  bark ;  b,  with 
bark  removed  show- 
ing bast ;  c,  with  bast 
removed  to  true 
wood.  (After  GolJian. ) 


RESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     51 


2a 


practically  survived  as  perfect  examples  or  in  the 
form  of  larger  connected  fragments,  but  mostly  are 
found  as  separated  portions  of  one  and  the  same 
plant  at  different  places — for  instance  the  stem  here, 
the  leaves  yonder, 
and  the  seeds  and 
fruit  somewhere  else. 
It  is  clear  that 
under  these  circum- 
stances it  is  only 
in  exceptional  cases 
that  the  properly 
associated  parts  can 
be  recognized  as 
such.1 

To  this  must  be 
added  that  one  and 
the  same  plant  occurs 
in  quite  different 
states  of  preserva- 
tion, with  or  without 
bark  (Fig.  10),  stone 
kernels,  pith  tubes, 
etc.,  so  that  quite 
different  forms  of  growth  may  present  themselves 
and  receive  also  different  names.  Fig.  10  will  help 
to  a  comprehension  of  this.  It  shows  us  three 

i  Dr.  W.  Gothan :  Entwicldung  der  Pflanzenwelt,  Osterwieck  am  Harz> 
1909,  p.  6.  This  little  volume  of  the  collection  Die.  Natur  is  much  to  be 
recommended.  We  shall  follow  it  generally  in  our  arguments.  Gothan 
obviously  relies  greatly  on  Potonie. 

E2 


FIG.  11. — REMAINS  OF  PLANTS  IN  SAMLAND 
AMBER. 

1.  Sambucus  (Elder)  Flower,  f  nat.  size. 
la.  The  same  magnified. 

2.  Portion  of  a  male  Oak'Catkin. 
2a.  The  same  magnified. 

3.  Cinnamon  Flower. 
3a.  The  same  magnified. 

(After  Gothan.} 


52  THE  THEOKY  OF  EVOLUTION 

conditions  which  may  be  easily  noted  in  the  same 
decayed  stem.  In  all  these  conditions  we  find  fossil 
trees.  Flowers  are  really  only  known  to  us  by  enclosure 
in  amber  (fossil  resin)  (Fig.  11). 

Nevertheless  it  is  possible,  though  certainly  only 
on  rough  lines,  to  conceive  an  idea  of  the  succession  of 
series  and  the  connection  of  the  greater  groups,  of  the 
process  of  transformation  within  separate  types  and  in 
some  degree  also  of  the  reasons  and  causes  of  same. 

§  1.    Brief    purview  of    the  chronological  succession    of 
the  larger  plant  groups. 

Gothan  adopts,  for  the  history  of  plant  life, 
a  somewhat  different  limitation  of  the  three  chief 
periods,  quite  logically  according  to  the  principles 
which  we  have  treated  more  in  detail  above.1 

According  to  this  the  Palaeozoic  era  closes  with 
the  lower  Permian,  the  Mesozoic  with  the  lower  Chalk 
where  the  Caenozoic  commences. 

(1)  Oldest  discoveries  of  plants. 

According  to  Gothan  2  the  graphite  masses  which 
are  found  even  in  the  Primary  rocks  (gneiss  and  Primary 
slate)  point  with  certainty  to  the  existence  of  organic 
growths.  Although  one  might  be  inclined,  owing  to 
the  dependence  of  the  animals  upon  plants,  to  deduce 

1  The  first  appearance  of  new  types,  high  development,  and  predomin- 
ance of  previously  sparsely  represented  ones  or  disappearance  of  other 
previously  most  diversified  forms.     (See  above,  p.  24.) 

2  Dr.  W.  Gothan :   Entwicklung  der  Pflanzenwelt,  Osterwieck  am  Harz, 
1909,  p.  15. 


RESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     53 

at  least  a  contemporaneous  origin  for  both,  yet  the 
occurrence  of  graphite  does  not  suffice  to  afford  a 
proof  of  this,  '  because/  as  Kayser  says,1  '  in  no  case 
should  the  accidental  chalk  and  graphite  deposits  of 
the  gneiss  be  regarded  as  proofs  of  organic  life  in  the 
Primary  period,  since  chalk  and  graphite,  as  it  can  be 
proved,  may  arise  also  on  inorganic  lines/ 

The  first  certain  traces  of  growth  in  recognizable 
remains  we  find  in  the  Silurian  formation.  The  alleged 
seaweeds  of  the  pre- Cambrian  and  Cambrian  systems 
must  to  a  large  extent  be  otherwise  explained. 

After  the  experiments  reported  by  Nathorsh  it  is 
impossible  longer  to  refrain  from  the  opinion  that  ca 
large  number  of  the  smaller  fossil  algae  are  either  the 
results  of  processes  in  rock  formation  or  animal  tracks, 
or  furthermore  are  produced  by  running  water  or  plants 
moved  by  water/  or,  as  is  stated  farther  on,  '  the  remains 
of  tissues  of  more  highly  organized  plants/2 

The  Silurian  remains,  fern  fronds,  and  large  masses 
of  algae  (bladder  algae — Siphonae),  show  us  that  there  were 
already  representatives  of  the  higher  systematic  groups. 
By  reason  of  the  simple  arrangement  of  the  veinlets  3  in 
the  fronds  the  first  ferns  are  designated  as  'primitive/  4 

1  Farmationskunde,  p.  21.     The    evidence   was   mainly   provided    by 
Weinschenk. 

2  A.  Schenk,  in  Zittel's  Handbuch  V,  p.  233.      By  this  the  existence 
of  vascular    plants  was    indicated.     More  details  cannot,   however,   be 
recognized  owing  to  the  great  decomposition  of  the  materials. 

3  The  veinlets  are  bundles  of  conducting  vessels  by  which  water  and 
earthy  salts  in  solution  are  carried  to  the  assimilating  tissues. 

4  More  details  are  given  in  §  3,  where  we  shall  treat  of  the  differentia- 
tion of  the  fern  type. 


54 


THE  THEORY  OF  EVOLUTION 


To  all  appearance  there  also  already  existed  in  the 
Silurian  era  the  predecessors  of  the  Sigillaria  (which 
developed  later  so  richly  in  the  Carboniferous)  (Figs.  12 
and  13)  in  the  form  of  Bothrodendrse,  if  the  age  of  the 

localities  of  the  finds  (Harz)   be 
correctly  estimated. 

Even  Grymnosperms  are  found 
already  in  the  group  of  Cordaitae  l 
which  also  play  a  very  prominent 
role  in  the  Carboniferous  system. 

(2)  The  further  development   of 
the  flora. 

In  the  Devonian  formation  the 


FIG.  12. — RECONSTRUCTED 
SIGILLARIA. 

a.  Flower.  6.  Leaves. 

st.  Rootstock  (stigmaria) . 


FIG.  13. — PORTION  OP  TRUNK  OF 
SIGILLARIA  SHOWING  VARIOUS 
STATES  OF  PRESERVATION. 

a.  Bark  entire. 

b  and  c.   Bark  removed. 


discoveries  of  land  or  rather  marsh  plants  become 
already  more  frequent.  With  the  ferns  there  appears 
a  further  group  of  the  highest  Cryptogams,  the  Proto- 
calamariacese  ;  these  are  the  Equisetum  trees — as  yet 
but  few  in  number  and  fairly  alike  among  themselves. 


1  Zittel's  Handbuch  V,  p.  251. 


RESULTS  OF  PAL^EONTOLOGICAL  RESEARCH     55 

By  the  evolution  of  numerous  variations  this  primary 
type  attains  its  period  of  maximum  development  also 
in  the  Coal  period. 

The  Cordaites  become  more  numerous ;  they  also 
begin  to  vary  in  form. 

In  the  Devonian  of  Bohemia  Potonie  has  found 
also  the  remains  of  Ginkgo-like  plants1  as  representa- 
tive of  a  further  group  of  Gymnosperms. 

In  the  coal  seams  of  the  Carboniferous  age,  accord- 
ing to  an  appropriate  remark  of  Potonie,3  tropical 
marshlands  (Sumpffiachmoore)  have  come  down  to  us 
in  a  fossilized  state,  and  by  both  these  terms — c  tropical ' 
and  (  marshland ' — the  flora  of  that  period  appears  to 
be  well  indicated. 

The  growths  which,  in  conjunction  with  flowering 
plants,  also  at  present  form  the  main  constituents  of 
such  '  reedbeds/  are  represented,  and  in  a  manner 
befitting  the  most  luxuriant  environmental  conditions, 
by  gigantic  tree-like  forms  of  the  three  classes  of 
Pteridophytes,  the  true  Ferns  ;  then  the  Club  Mosses 

1  J.   P.    Lotsy :    Vorlesungen  uber  Descendenztheorien  (Hit  besonderer 
BeriicJcsichtigung  der  Botanischen  Seite  der  Frage)  II,  Jena,  1908,  p.  466. 
The  Ginkgos  externally  resemble  our  leafy  trees.     The  only  species  still 
existent — Oinkgo  biloba  (on  account  of  the  two-lobed  leaves) — is  indigenous 
in  China  and  Japan,  but  as  quite  solitary  specimens.     It  may  frequently 
be  seen  in  our  parks.     They  form  a  quite  peculiar  group,  which  Lotsy  thus 
describes :   '  Gymnosperms  with  conifer-like  wood  with  male  and  female 
inflorescence  widely  differing  from  the  Cycads,  but  with  ovaries  and  seed 
resembling  those  of  Cycads.' — Lotsy :  Vortrdge  tiher  Bot.  Stammesgeschichte, 
II,  Jena,  1909,  p.  778.     (Not  to  be  confounded  with  the  work  above 
cited. )     (Cycads  and  conifers  are  two  chief  groups  of  recent  Gymnosperms. ) 
The  Ginkgo  was  therefore  no  more  a  transitional  form  in  the  Carboniferous 
period  than  it  is  to-day,  as  we  shall  see  later  on. 

2  Die  Entstehung  der  Steinkohle,  etc.,  p.  186. 


56  THE  THEORY  OF  EVOLUTION 

(Lepidodendron)    (Fig.     14),    and    Sigillaria1    and   the 
Calamites. 


FlG.  15. — A  RECONSTRUCTED  CORDAITE. 

FIG.   14. — A  RESTORED  LEPiDO-  The  flower  scapes  may  be  seen  on  the 

DENDRON.  separate  branches  between  the  leaves. 

The  Gymnosperms  are  represented  by  the  Corda- 
ites  (Fig.  15),  which  soon  disappeared ;  they  were 
large  trees  with  sometimes  gigantic  leaves,  which  there- 

i  Schuppenbaume  (lit.  scale  trees :  Lepidodendrse)  derive  their  name 
from  the  cushion-like  elevations  (scales)  on  the  bark  which  bear  the  scars  of 
the  fallen  leaves.  The  Sigillaria  (lit.  seal  trees)  do  not  show  these  cushions 
or  scales  ;  the  leaf  scars  lie  flat  upon  the  bark,  and  are  hexagonal. 


RESULTS  OF  PAL^ONTOLOGICAL  RESEARCH     57 

fore  do  not  agree  at  all  with  the  needles  and  various 
foliage  of  our  Gymnosperms  but  are  rather  remindful 
of  the  parallel-veined  ones  of  the  Monocotelydons 
(e.g.  the  Liliaceae). 


FIG.  16. — RECONSTRUCTION  OF  A  TRUNK  or  LYGINODEN- 

DRON  OLDHAMIANUM,  A  FERN-LIKE  GYMNOSPERM. 

(After  Scott.) 

The  three  smaller  branches  seen  at  the  top  of  the 
figure  with  contracted  apparent  leaves  are  regarded  as 
the  inflorescence,  with  the  empty  seed-vessels  at  the  ends 
of  the  stalks.  (After  Oliver.) 

Until  recently  it  was  a  standing  expression  in  all 
text-books  that  the  Palaeozoic  age,  and  particularly  that 
of  the  Coal  period,  formed  the  epoch  of  fern  growth, 
i.e.  of  seedless  plants.  Kecently,  however,  a  whole 
series  of  families  which  until  then,  owing  to  the  form 


58 


THE  THEORY  OF  EVOLUTION 


of  their  foliage,  had  been  regarded  as  true  ferns,  have 
had  their  systematic  classification  entirely  upset.  It 
was  found,  for  instance,  that  a  number  of  isolated  seeds 
could,  with  a  probability  bordering  on  certainty,  be 
associated  with  '  fern  '  leaves  and  '  fern  '  stems.1 

Oliver  and  Scott 
particularly  and 
Stur  previously  have 
done  meritorious 
service  in  the  deter- 
mination of  this 
most  important  dis- 
covery. 

Figs.  16  and  17 
show  a  '  fern '  stem 
and  the  seed  belong- 
ing thereto,  which 
in  exterior  form 
resembles  a  hazel  nut.  The  new  group  of  these 
Carboniferous  Gymnosperms  received  the  provisional 
names  of  '  Pteridospermen/  i.e.  seed-plants  with  fern- 
like  foliage.  They  are  not  intermediate  forms  since 
there  are  to-day  Gymnosperms  with  fern-like  leaves, 
e.g.  the  sago  or  fern  palms. 

We  observe  then,  in  the  history  of  the  plant  world, 
that  with  the  progress  of  palaeontology  the  systematic 

1  Compare  with  this  the  instructive  statement  by  F.  W.  Oliver :  Ueber 
die  neuentdeckten  Samen  der  Steinkohlenform,  in  the  Biol.  Zentralblatt,  1905, 
p.  401;  Lotsy:  Vortrdge  uber  Bot.  Stammesg.,  II,  p.  706;  Potonie,  in 
the  collected  work,  Die  Natilrlichen  Pflanzenfamilien-,  published  by  Engler 
and  Prantl :  I,  Part  iv,  p.  780. 


FJO.  17.— The  seed  (L.  Oldhamianum,  Fig.  16)  is 
enclosed  in  a  husk  which  is  covered  with 
glands.  (After  Biol  Zentralblatt.) 


RESULTS  OF  PAL^EONTOLOGICAL  RESEARCH     59 


groups  of  higher  standing  must  be  referred  to  an  older 
and  older  period.  '  It  is  not  long  ago/  says  Lotsy, 
'  that  it  was  thought  that  the  seed-bearing  plants 
were  of  comparatively 
recent  origin  and  that 
at  least  in  the  Coal 
period  they  were  en- 
tirely absent/  Now 
the  Cryptogams  (non- 
seed-bearing  plants) 
are  not  even  conceded 
predominance  in  the 
later  Palaeozoic  period 
(Fig.  18).  '  Gradually 
the  Ferns,  one  after 
the  other,  showed 
themselves  to  be  seed- 
bearers,  and  it  is  diffi- 
cult to  say  to  what 
number  relatively  this 
alteration  will  extend. 
It  will  probably  be  a 
large  one/  ] 

Yet  must  we  agree 
with  Gothan's  warning  against  over-hasty  conclusions.2 
The  true  fern  nature  of  a  leaf  is  certainly  only 
beyond  all  doubt  when  we  find  the  spore  heaps 
on  the  under  side  of  the  foliage  or  elsewhere,  since 
thereby  they  are  directly  shown  to  be  spore-bearing 

1  Biol  Zentralblatt,  1905,  p.  414.         2  Entwicklung  der  Pftanzenwelt,  p.  35. 


FIG.  18.— ANG,  Angiospermse;  CON,  Coni- 
ferse;  COR,  Cordaiteae;  CYC,  Cycado- 
phyta  ;  EQ,  Equisetinese ;  F,  Filicineae ;  G, 
Ginkgoales;  LYC,  Lycopodineae ;  PT, 
Pterido  sperm  se  or  Cycadofilices ;  S, 
Sphenophyllales. 
It  is  seen  that  the  Palaeozoic  seed-bearing 

plants — PT  and  COR — approximately  equal 

the  non-seed-bearing,  F,  LYC,  S,  and  EQ. 

(After  Oliver.) 


60  THE  THEORY  OF  EVOLUTION 

plants  (not  seed-bearing).  But  even  the  constant 
absence  of  spore-heaps  by  itself  is  no  proof  that  the 
leaves  belong  to  a  seed-bearing  plant,  since  ferns  can 
propagate  themselves  purely  vegetatively  by  stolons 
and  offsets. 

Lepidodendrons,  Sigillaria,  and  Cordaites  die  out 
in  the  Old  Red  Sandstone— that  is  in  the  formation  im- 
mediately succeeding  the  Carboniferous.1  As  separate 
individuals  and  species  here  for  the  first  time  appear 
clear  remains  of  Ginkgo  trees,  also  Conifers  (Walchia) 
which  are  related  to  the  Araucarias  2  and  Cycads. 

In  the  Permian  limestone  the  development  of 
the  new  forms  commences  vigorously,  the  gigantic 
Pteridophytes  and  the  Cordaites  have  disappeared, 
so  that  there  is  a  sufficient  reason  for  beginning,  with 
the  Permian  limestone,  a  new  period — the  Mesozoic— 
which  shall  be  '  the  era  of  the  Gymnosperms/ 

Angiosperms,  i.e.  flowering  plants  with  covered 
seeds,  which,  as  Monocotyledons  and  Dicotyledons, 
form  the  great  bulk  of  our  present  flora,  are  absent  in 
the  Mesozoic  period.  The  groups  of  Gymnosperms 
develop  more  and  more  the  forms  which  approximate 
nearest  to  our  present  ones.  In  the  Chalk  our  species 
are  already  to  be  found. 

In  the  lower  Chalk  there  appear  the  first  remains 
of  flowering  plants  :  therewith  begins  the  Csenozoic 

1  In  the  Red  Sandstone  we  meet  again  with  some  traces.     They  appear 
then,  however,  to  be  entirely  extinct,  i.e.   leaving  no  successors  even  of 
different  appearance. 

2  Araucarias  are  represented  by  the  so-called  '  monkey  puzzles  '  which 
are  frequently  cultivated. 


RESULTS  OF  PAL^ONTOLOGICAL  RESEARCH    61 

period.  f  These  new  plants,  almost  from  the  very 
commencement,  appear  in  such  quantities  that  the 
Gymnosperms,  which  earlier  predominated,  to  say 
nothing  at  all  of  the  Ferns,  etc.,  had  to  retreat  to  the 
background/  l 

The  classification  of  the  separate  families  depends 
upon  the  leaves,  which  in  most  cases  naturally  cannot 
secure  absolute  certainty.  Stems  are  rare  and  the 
flowers  we  know  really  only  by  enclosures  in  amber. 
The  Catkin-bearers  and  the  Laurel  family  are  in  any 
case  very  old  groups.  Since  the  Oligocene  period 
we  find,  in  ever  greater  numbers,  specie's  similar 
to  or  quite  like  the  present  ones,  and  often  quite 
'  specialized/  In  the  Pliocene  there  already  lived,  for 
example,  the  Silver  Poplar,  the  Aspen,  the  Red  Beech, 
the  Mountain  Maple,  etc. 

Conclusions  from  §  1. 

(1)  The  earliest  history  of  the  plant  world  is  so  far 
entirely  unknown  to  us ;    we  know  neither  when  the 
first  growths  appeared,  nor  how  they  looked. 

(2)  It  must  be  accepted  that  already,  at  the  time 
when    the    Cambrian    and    pre-Cambrian    formations 
were  deposited  and  the  animal  world  was  already  so 
grandly   developed,    a  rich   flora   of  some   kind    also 
existed,  since  the  animal  world  is  dependent  upon  the 
plant  world. 

(3)  Despite  the  great  imperfection  of  the  evidence 
obtained,   and  the   fact  that   it  is    only  remains    of 

1  Gothan  :  Entwicklung  der  Pflanzenwelt,  p.  86. 


62  THE  THEORY  OF  EVOLUTION 

inhabitants  of  damp  and  humid  habitats  that  have 
been  preserved  in  great  numbers  which  do  not  permit 
of  an  absolutely  certain  decision,  it  is  very  probable 
that  the  Gymnosperms  followed  the  Pteridophytes 
and  the  Angiosperms  the  Gymnosperms.1 

§  2.  Inter-relations    between    the   larger  groups,  families 
(series),  and  classes. 

As  above  for  the  animal  world,  we  put  the  question 
also  here,  whether  the  larger  groups  were  derived 
from  each  other  in  succession,  so  that,  for  instance,  the 
Angiosperms  represent  only  a  higher  development  of 
the  Gymnosperms. 

(1)  In  the  system  generally  in  use,  there  stand  upon 
the  lowest  step  the  so-called  Thallophytes  (Algse  and 
Fungi),  then  follow  the  Mosses,  the  Ferns  (really  ferns), 
Club  Mosses,  Equisetums,  and  Hydropterides  (Water- 
Ferns),  the  Gymnosperms,  and,  finally,  the  Angiosperms 
(Monocotyledons  and  Dicotyledons). 

Whence  the  Ferns,  the  first  indubitable  plant  re- 
mains, come,  no  one  knows.  In  the  pre-Silurian  forma- 
tions we  know  certainly  of  no  mosses  which,  purely  a 
priori,  come  next  to  them  in  consideration,  and  not 
even  of  clear  traces  of  Thallophytes  which  permit  of 
any  recognizable  connection  with  ferns. 

1  By  '  Ferns,'  '  Gymnosperms,'  and  '  Angiosperms  '  we  mean  here  only 
those  foliage  plants  or  trees,  in  short,  those  forms  which  the  layman  finds 
so  named  only  in  botanical  works.  Science  differentiates  all  these  plants 
by  a  double  generation  (of  which  more  later).  The  sense  of  our  above 
remark  is  simply  that  Ferns,  Gymnosperms,  etc.,  followed  each  other 
successively. 


KESULTS  OF  PAL^EONTOLOGICAL  RESEARCH     63 

(2)  The    G-ymnosperms    are   themselves    very   old 
forms  :    judging  only  by  the  palseontological  remains, 
they  belong  to  the  oldest  flora.     Of  a  genetic  connec- 
tion with  ferns  or  other  plants  there  is  naught  to  be 
said. 

The  new  class  of  (  Pteridosperms  '  of  the  Carboni- 
ferous formation  changes  nothing  in  this  respect, 
since  despite  the  fern-like  foliage  they  form  no  inter- 
mediate link  between  Ferns  and  Gymnosperms  but, 
as  seed-bearing  plants,  are  pure  Gymnosperms.  Even 
to-day  we  have,  among  the  Cycads,  which  are  true 
Gymnosperms,  forms  with  fern-like  foliage  ;  and  one 
Cycad  (Stangeria  paradoxa)  (a  species  now  existent) 
ranked  long  as  a  fern,  until  its  flowers  were  discovered.1 

The  determination  of  the  systematic  classification 
must,  even  according  to  Potonie,2  who  is  a  strong 
advocate  of  transitional  forms,  be  made  dependent 
upon  the  discovery  of  the  seed  or  of  the  spore  heaps. 
If  seed  be  found  then  the  foliage  and  stems  appertain- 
ing thereto  are  those  of  true  seed-bearing  plants,  in 
the  other  case  they  are  true  ferns.  He  himself  grants 
that  agreement  in  many  anatomical  characters— thick- 
ness of  growth,  venation,  form  of  leaf — may  all  be 
attributed  to  '  adaptation  to  the  same  mode  of  existence/ 

(3)  Eepresentatives  of    the    true  flowering    plants 
or    Angiosperms  c .  .  .  appear    at  first    in  the    Chalk 
and  in  forms  of  such  high  organization  as  to  agree 

1  Gothan,  p.  35. 

2  Engler  and  Prantl  :   Die  Naturlichen  Pflanzenfamilien,  I,  Part   iv, 
p.  789. 


64  THE  THEOKY  OF  EVOLUTION 

with  the  Dicotyledons  of  the  present  day.  Precursors 
of  these  first  Dicotyledons  belonging  to  older  forma- 
tions are  entirely  unknown  to  us/  l  We  have  already 
emphasized  above  the  fact  that  the  highest  systematic 
group  appeared  at  the  outset  as  a  numerous  one  and 
in  genera  and  families  which  are  still  existent.  With 
regard  to  the  relations  of  the  Angiosperms  to  the  Grymno- 
sperms  Reinke  says  :  3  '  No  closer  relations  of  any  kind 
can  be  traced  between  the  oldest  Angiosperms  and  the 
Gymnosperms.  Both  chief  sections  of  flowering  plants 
are  as  sharply  separated  in  their  fossil  types  as  they 
are  as  living  plants/ 

(4)  It  should    also   be  considered   that  as   regards 
the  history  of  the  Mosses  and  the  oldest  Thallophytes 
we   know  practically   nothing,   despite   that   the   con- 
ditions of  preservation  for  the  associated  mosses  were 
favourable,   growing  as  they  often  did  in  damp  and 
humid  habitats.3    Hence  it  is  seen  that  regarding  the 
historic  (phyletic)  development  of  the  flora  we  can  say 
nothing  with  certainty. 

(5)  The   question  whether  within  the  limits  of  one 
and  the  same  type — for  instance  the  Lepidophyte  class — 
the  higher   orders  appear  after  the  lower  cannot  be 
determined  in  the  absence  of  objective  evidence.     It 
appears,  however,  to  be  very  probable  that  the  changes 

1  Reinke :  Naturwiss.  Vortrdge,  Vol.  I,  p.  28. 

2  Reinke  :   Philosophic  der  Botanik,  Leipzig,  1905,  p.  135. 

3  Gothan  :   Entwicldung  der  Pflanzenwelt,  p.  96.     Even  in  the  Carboni- 
ferous formations  mosses  cannot  be  clearly  made  out.     '  The  question  of 
fossil  mosses,  owing  to  these  circumstances,  has  been  a  source  of  much 
brain-racking  among  the  palaeontologists.' 


KESULTS  OF  PAL^EONTOLOGICAL  KESEARCH      65 

which  the  Lepidophytes,  or  the  Equisetae  for  instance, 
experienced  in  the  course  of  geological  periods  represent 
a  simple  change  of  form,  a  specialization  of  one  and 
the  same  grade  of  organization  in  varied  directions. 
The  reasons  for  this  we  will  at  once  present. 


§  3.  Description  of  changes  actually  observed  and  the 
probable  causes  of  same  ('  Palceontological  Law 
of  Evolution '). 

The  transformation  of  the  plant  world  is  much  less 
than  is  generally  supposed.  It  is  true  that  we  read  in 
all  tuition  books  that  the  Coal  flora,  the  New  Ked  Sand- 
stone flora,  and  others,  are  fundamentally  different  from 
each  other  and  from  that  of  the  present  day.  In  the 
wall  cartoons  of  Potonie  this  is  shown  in  the  clearest 
way.  These  pictures  show  exactly  the  flora  actually 
found  in  the  formations  concerned,  but  as  regards  the 
extent  of  the  transformation  established  in  single 
definite  groups  a  mere  comparison  between  two  or 
more  such  '  landscapes  9  can  teach  us  very  little. 

This  is  because,  first  of  all,  in  most  cases  it  is  only 
parts  of  the  flora  concerned  which  are  shown — for 
instance,  moor  plants  :  consequently  moor  should  be 
compared  with  moor.  Furthermore,  the  climate  at 
the  time  concerned  must  be  considered  :  the  tropical 
flora  of  the  Coal  era  has  its  descendants  mostly  in  the 
tropics.  Finally  it  must  not  be  forgotten  that  plant 
groups  can  die  out  and  become  extinct  and,  indeed, 


66 


THE  THEORY  OF  EVOLUTION 


have  done  so  frequently.1  It  would,  then,  be  vain  to 
look  for  representatives  of  such  types.  The  presence 
of  a  single  group  of  this  kind,  especially  when  it  is 
numerically  strong,  naturally  gives  to  a  formation 
quite  a  different  appearance  in  comparison  with  all 
others  in  which  the  group  is  lacking. 


Fit;.  19. — a,  CALAMITES   Luckowic.      &,  ASTERO- 
CALAMTTES    scrobiculcttus.     Kulm.    Astero-cala- 
mitcs   belongs    to    the  Protocalamariacese  and 
shows  the  course  of  the  furrows  as  described. 
(After  Gotlmn.) 

If  this  be  borne  in  mind,  then  the  transformation 
of  the  plant  world  loses  much  of  its  '  magnificence/ 

With  this  preliminary  remark  we  will,  by  several 
examples,  show  of  what  kind  are  the  transformations 
observed  and  to  what  causes  they  may  be  imputed. 

1  As  such  extinct  plant  forms  there  are  regarded  for  instance  the 
Cordaites  of  the  Coal  Age,  and  mostly  also  the  Lepidodendron  and  Sigillaria 
and  other  smaller  sections.  Steinmann  (Die.  Gcolog,  Grmidlagen  der  Abstam- 
mungslelire,  1908,  p.  20)  will  not  hear  of  '  dying  out '  in  the  sense  of 
actual  disappearance.  Therein  he  goes  too  far,  since  the  extinction  of 
extremely  specialized  forms  involves  no  improbability. 


EESULTS  OF  PAL^ONTOLOGICAL  RESEARCH    67 

(1)  The  Law  of  Specialization  (Differentiation). 

(a)  The  Calamariacese  Series. 

In  the  Devonian  formation,  probably  already  in 
strata  which  may  be  ascribed  to  the  Silurian  period, 
there  are  found  the  first  remains  of  Equisetse — the  so- 
called  Protocalamariacese.  In  the  upper  productive 
coal  formations  these  primary  Equisetse  become  Cala- 
mariacese.  How  did  that  occur  ?  The  Protocalamari- 
aceae  show  clearly,  in  the  stone  kernels  preserved,  the 
impressions  of  the  main  vein  fascicles  running  upwards 
in  the  stem  in  the  form  of  longitudinal  furrows  (Fig.  19) 
which,  as  opposed  to  those  of  the  Calamariaceae  in  the 
separate  nodes  of  the  stem,  lie  exactly  in  line  with 
each  other  ;  in  the  Carboniferous  forms,  on  the  other 
hand,  each  furrow  ends  between  two  of  the  furrows  of 
the  upper  node.  Now  it  can  be  accepted  as  quite 
certain  that  this  alteration  had  a  definite  purpose 
because,  as  Haberlandt  in  his  excellent  work1  points 
out,  the  formation,  position,  and  direction  of  the  vas- 
cular bundles  stand  in  the  closest  possible  relation  to 
the  physiological  needs.  To  what  new  life  conditions 
these  old  Equisetse  conformed  thereby  we  naturally 
cannot  say  with  our  present  knowledge.  This  question 
can  only  be  solved  by  constant  consideration  of  the 
present  '  adaptive  evidence/ 

If  we  now  consider  that  the  Protocalamariaceoe 
groups  only  occur  in  the  oldest  strata  of  the  coal 

1  G.  Haberlandt :  Physiologische  Pftanzenanatomie,  Leipzig,  1909,  p.  338, 

F2 


THE  THEORY  OF  EVOLUTION 


formations  and  in  the  Devonian 1  formation,  widely 
extended  over  the  world  it  is  true,  but  only  in  a  few 
and  similar  forms,  while  the  Calamariaceae  appear  in 
several  families  and  individually  in  greater  number, 
we  come  near  to  the  conclusion  that  under  the  luxurious 
conditions  of  existence  in  the  Carboniferous  era 2 

a  wide  development 
of  the  Calamariaceae 
type  took  place  in 
various  directions  ac- 
cording to  the  nature 
of  the  habitat.  That 
would  be  a  case  of 
differentiation  of  a 
type. 


(6) 


The     Fern 

Series. 


FIG.  20. — a,  SPHENOPTERIDIUM  furcillatum  ; 
Silurian  ;  Heffen,  Nassau.  6,  S.  dissectum  ; 
Kulm ;  Rothwalthersdorf,  Lower  Silesia. 
Primary  venation.  (After  Gotlian.) 


The  classification 
of  the  fossil  ferns  is 
effected  for  purely 
practical  reasons  ac- 
cording to  the  '  venation '  and  according  to  the 
mode  of  attachment  of  the  pinnae  (subdivisions)  to 
the  stalk.  The  oldest  ferns,  the  Archeeopteridse,  show 
a  fan-like  venation ;  all  the  veins  are  of  the  same 
thickness  and  radiate  from  about  one  point 3  (Fig.  20). 

1  According  to  Zittel:    Handbuch  der  Paldontologie,  V,  p.  176.    Gothan 
puts  a  note  of  interrogation  against  Devonian. 

2  Potonie :  Die  Entstehung  der  Steinkohle,  etc.,  p.  152. 

3  Gothan  :  Entwicklung  der  Pflanzemvelt,  p.  21, 


RESULTS  OF  PAL^ONTOLOGICAL  RESEARCH      69 


With  the  chronologically  later  ferns  the  venation 
becomes  feathered,  i.e.  there  are  continuing  main  veins 
with  lateral  branching  minor  ones  (Fig.  21). 

In  the  rich  Carboniferous  flora  there  then  appear 
fronds  with  reticulated  venation  in  which  the  lateral 
branch  veins  are  united  together  by  numerous  short 

b 


FIG.  21. — a,  PECOPTERIS  creopteridia,  Saar 
district,  b,  c,  d.  Fronds  (parts  of)  of  various 
ferns,  showing  spore  heaps  on  the  under 
side.  (After  Gotfian.) 


FIG.  22. — a,  ALETHOPTERIS  Serli, 
Saar  district,  b  shows  reticulate 
venation.  (After  Gothan.) 


connective  ones  (anastomosing)  (Fig.  22,  b).  From 
the  purely  comparative  point  of  view  the  reticulate 
venation  is  decidedly  an  advance  over  the  feathered 
venation,  and  this,  in  its  turn,  over  the  fan  venation.1 

1  Haberlandt :  Physiologische  Pftanzenanatomie,  Leipzig,  1909,  p.  348. 
Haberlandt  describes  two  chief  types  of  venation  in  leaves.  The  first,  in 
which  the  veins  proceed  separately  (without  anastomosing),  appears  as  a 
rule  in  such  leaves  as  never  require  much  water  or  nutriment  on  account 
of  their  smallness  or  trifling  transpiration,  and  show  assimilative  activity. 
The  second  type  (reticulated)  appears  in  leaves  of  the  opposite  character. 
*  Thus  (by  this  venation)  the  leaf  area,  with  the  least  possible  length  of 
veins,  becomes  uniformly  and  by  the  shortest  way  supplied  with  water 
and  nutritive  salts '  (p.  349). 

\ 


70 


THE  THEORY  OF  EVOLUTION 


Since  now  chronologically  also,  from  the  Silurian 
to  the  upper  productive  coal  measures,  the  said  evolu- 
tionary forms  follow  each  other,  therefore  the  Ferns 
appear  to  present  an  evolutionary  series  and  the 
preliminary  of  the  transformation  itself  to  have  been 
a  differentiation  of  the  original  Archseopterid  type. 
The  external  cause  we  cannot  discuss,  since  with  the 
palseontological  evidence  we  have  only  to  compare 
the  results  of  vital  processes  with  each  other. 


•-:g 

I 


FIG.  23. — a,  &IGILLAJUA  Brardi  (leiodermic)  from  the  upper  productive  Car- 
boniferous formation  of  Wettin.  b,  8.  Blob  ay  (rhytidolepic)  from  the 
middle  productive  Carboniferous  formation  of  the  Ruhr  district,  c,  S. 
elegant  ula  (' favularic,'  ex  same),  d,  SYRJXGODENDROX  (state  of  preserva- 
tion), c  and  d  show  how  different  states  of  preservation  occur  by  removal 
of  separate  bark  layers.  (After  Got  ha  n.) 

(c)  The  Sigillaria  Series. 

A  similar  transformation,  though  caused  by  changed 
external  conditions;  we  can  follow  up  with  the  fossil 
Sigillaria, 

According  to  the  arrangements  of  the  leaf  scars 
the  Sigillaria  have  been  classified  as  '  favularic  '  when 
they  stand  quite  close  together  in  sloping  lines, 
'  rhytidolepic  '  when  they  appear  in  longitudinal  rows 
with  furrows  between,  '  leiodermic  '  where  the  scars 
stand  quite  separated  on  the  bark  without  longitudinal 


RESULTS  OF  PAL.EONTOLOGICAL  RESEARCH     71 

divisions  (Fig.  23).  In  the  said  succession  the  Sigillaria 
form  actual  guides  l  for  the  various  successive  geological 
horizons.  In  this  way  they  divide  themselves  and 
form  as  a  whole  a  connected  series  by  descent.  The 
actual  causes  and  the  purpose  of  the  described  trans- 
formation must  be  deduced  from  observations  of  the 
plants  at  present  living. 

The  G-inkgos  show,  particularly  in  the  Jura  forma- 
tion, a  great  multiformity  in  the  make  of  the  leaves 
which  are  of  value  as  indicative  characters  for  the 
various  systematic  species  and  genera  (specialization). 
In  a  general  way  separate  links  may  be  determined 
in  the  transformation  of  many  other  families  which 
eventually  have  led  up  to  the  present  ones,  but  regard- 
ing the  details  of  the  process  we  are  not  sufficiently 
instructed.3 

(2)  Phenomena  of  Convergence  (p.  45). 

By  convergence  is  understood  the  formation  of  like 
or  very  similarly  constituted  organs,  or,  if  the  organs 
already  exist,  of  similarities  of  structure  and  form  in 
organisms  which  according  to  their  total  type  belong  to 
different  systematic  categories.  Under  some  circum- 
stances the  limitations  of  such  converging  groups  may 
naturally  be  rendered  difficult. 

It  has  long  been  remarked  that,  for  instance, 
the  Carboniferous  flora  appears  outwardly  of  a  fairly 

1  Gothan  :  Entwicklung  tier  Pflanzenwett,  p.  41. 

2  Reinke  :  Philosophic  dcr  Botanic,  p.  136.     '  Actual  transitional  forms 
between  Tertiary  species  and  living  species  cannot  be  followed  up  with  the 
desired  clearness.'     (Reinke  speaks  here  of  flowering  plants.) 


72  THE  THEORY  OF  EVOLUTION 

uniform  stamp,  which  can  easily  induce  the  idea  of 
close  relationship  and  in  some  cases  has  even  led  to  the 
putting  forward  of  mixed  types  or  transitional  forms. 
Now,  however,  we  can  impute  many  peculiarities 
of  the  great  groups  of  the  Carboniferous  flora  to  con- 
vergence without  conflicting  with  the  facts  observed. 
The  increase  of  thickness  of  the  stem  by  means  of  a 
constantly  present  embryonal  tissue  (Cambrian)  in 
many  of  the  Lepidophytes  and  the  Calamariacese, 
the  possession  of  large  subterranean  rhizomes  *  (Stig- 
maria),1  the  club-like  thickening  of  the  stem  below, 
the  possession  of  a  smooth  trunk  without  bark,  the 
formation  of  stomata  on  the  stem  or  in  organs  proper 
(Pneumatophora),  can — nay,  must — be  regarded  as 
adaptive  factors  to  the  like  environmental  conditions. 
The  proof  of  this  has  been  provided  by  Potonie  in  his 
work  already  mentioned  ~  in  the  most  convincing  manner 
by  the  comparative  study  of  the  Carboniferous  flora 
and  that  of  an  existing  tropical  marshland.  Indepen- 
dently of  the  systematic  differences  between  the  fossil 
and  the  present  moor  flora — in  the  Carboniferous  era 
Pteridophytes  and  Gymnosperms  and,  in  the  equivalent 
tropical  moorland  of  Sumatra,  Dycotyledons — the 
peculiarities  of  both  flora  are  unequivocally  explained 
by  the  mode  of  life  under  the  same  conditions. 

1  Rhizomes  (root-stocks)  are  extensions  or  thickenings  of  the  under- 
ground stem,  from  which  the  roots  proper  issue.     The  '  stigmaria  '  are  very 
widely  projecting  twice-branched  formations,  whose  surface  is   covered 
with  round  scars  (whence  the  name  stigmaria)  spirally  arranged,  which 
stand  far  apart  from  each  other,   and  sometimes  bear  round  rootlets. 
E.  Frans  :  Der  Petrefactensammler,  Stuttgart,  1910,  p.  48. 

2  Die  Entstehung  der  Steinkohle,  u.  s.  w.,  pp.  152, 166,  and  169  (tables). 


RESULTS  OF  PAL.EONTOLOGICAL  RESEARCH     73 

It  does  not  therefore  follow  from  the  fact  that  in 
the  Carboniferous  formation  many  ferns  formed  actual 
trunks,  that  they  are  really  related  to  the  Gymnosperms 
(Pteridosperms).  On  the  other  hand  there  may  be 
Gymnosperms  (the  said  Pteridosperms)  with  fern-like 
foliage.1 

In  the  coal  strata  of  the  Tertiary  formation  the 
flora  of  the  present-day  moors  is  much  more  similar, 
'  since  these  formations  contain  many  genera  and  species 
of  plants  which  still  exist/  In  North  America  we  have 
to-day  '  very  extensive  moors  with  a  plant  community 
of  which  a  considerable  number  of  species  are  the  same 
as,  in  the  Miocene  period,  occupied  our  moors/  3 

(3)  Phenomena  of  Retrogression  (p.  44). 

If  our  present  Equisetse  be  compared  with  the 
Calamariacese  of  the  Carboniferous  period,  which  are 
closely  allied,  a  general  degeneration  of  those  gigantic 
tree-like  growths  might  be  assumed.  In  nearly  all 
educational  books  indeed  we  find  the  same  observation 
—that  our  Equisetums,  as  small  insignificant  weeds, 
of  such  great  uniformity  of  make  that  all  the  species 
only  form  one  genus,3  are  the  degenerated  dwarfed 
descendants  of  those  fossil  trees.  If  that  be  so,  we 

1  In  this  case  it  is,  in  addition,  quite  immaterial  whether  the  fern  type 
of  the  leaf  be  regarded  as  evidence  of  convergence  or  not,  since  even  to-day 
Gymnosperms  exist  with  such  foliage — the  Cycads  (Fern  Palms) — which, 
however,  are  not  therefore  regarded    as    '  intermediate    forms.'     Oliver 
(Biol  Zentralbfatt,  1905,  p.  403)  constantly  speaks  of  *  intermediate  forms  * 
(Zwischenformen). 

2  Potonie  :  Die  Entstehung  der  Steinkohle,  etc.,  p.  185. 

3  Warming :  Systematische  Botanik,  p.  151. 


74 


THE  THEORY  OF  EVOLUTION 


have  certainly  here  a  good  example  of  a  general  retro- 
gression before  us.  That  would  not  be  an  impossibility, 
since,  supported  by  the  comparative  study  of  the  present 
moorland  flora  and  the  fossil  one,  the  thickening  of  the 
stems,  the  abundant  ramification  of  the  lateral  growths, 

the  form  of  the 
leaves,  which  are 
not  increased  in 
area  but  only  split 
up  (Fig.  24),  may 
all  be  imputed  to 
the  influence  of  the 
favourable  environ- 
ment in  the  Carbon- 
iferous period.  If 
such  conditions 
cease,  naturally  all 
the  special  con- 
forming structural 
arrangements  cease 
also.  Therefore  the 
lack  of  thickened 

stems,  the  reduction  of  leaf  area,  and  the  reduced 
branching  of  the  present  forms,  can  scarcely  be  called 
an  actual  degeneration.  But  in  the  Carboniferous 
period  there  were  in  all  probability  weed-like  small  forms 
as  well  as  the  gigantic  ones  ;  l  and  from  these  we  might 
well  attempt  to  deduce  the  modern  Equisetae.  Certain 
it  is  that  the  existence  of  small  club-mosses  is  proved. 

1  Gothan  :  Entivicklung  der  Pflanzenwelt,  p.  51. 


Fie.  24. — CALAMAKIA  FOLIACE.    (After 

a,  Asterophyllites  equisdiformi-s  :  Carboni- 
ferous, Harz.  b,  Annular  ia  splienophyl- 
Idides ;  ZAvichau.  c,  A.  radial  a  ;  Lo\\er 
Silesia.  The  leaves  have  not  assumed  scale- 
like  forms  as  have  the  present  ones. 


RESULTS  OF  PAM;ONTOLOGICAL  RESEARCH   75 

The  Calamites  we  no  longer  find  in  the  following 
formations,  but  throughout  the  whole  Mesozoic  forma- 
tions we  find  true  Equisetse  (like  the  modern  ones  with 
slender  branched  foliage),  as  also  in  the  Permian,  Red 
Sandstone,  Jura,  etc.,  which  alter  but  little.  Among 
these  are  large  forms,  of  which  we  retain  an  example  in 
the  present  Equisetum  giganteum,  ten  to  thirty  feet  high. 

It  is  to  be  expected  that  from  the  outset  retro- 
gressive phenomena  should  play  a  considerable  role 
in  the  history  of  the  plant  world  and  largely  contri- 
bute to  shape  new  forms,  but  it  might  be  difficult 
to  produce  the  necessary  fossil  proofs.  We  deduce 
this  rather  from  the  so-called  '  rudimentary '  structures 
of  the  present  plants,  particularly  parasitic  ones. 

Conclusions  deduced  from  palaeolithic  botany. 

If  it  be  granted  that  the  forms  of  growth  of  syste- 
matically higher  rank  appeared  chronologically  subse- 
quently to  the  lower,  yet  there  is  absolutely  no  indicative 
proof  in  the  case  of  any  one  group  (family  or  class) 
that  they  were  developed  from  the  lower  forms.  In 
this  botanists  are  entirely  in  agreement  in  so  far  that 
no  one  speaks  of  an  actual  '  proof  '  which  can  be  pro- 
duced in  the  shape  of  fossil  evidence  of  transitionalforms.1 

1  See,  for  instance,  Zittel's  great  work,  the  fifth  volume  of  which  is 
elaborated  by  two  distinguished  botanists,  Schimper  and  Schenk.  The 
expressions  used  of  '  possibility,'  '  perhaps,'  etc.,  evidently  show  that  no 
proof  has  been  afforded.  Furthermore,  see  Reinke,  ISchwendener,  Haber- 
landt,  Potonie,  Gothan,  Steinmann,  Kothen,  Deperet,  Kerner  v.  Marilaun, 
and  Neumayr.  Certainly  in  many  works  we  must  differentiate  between 
what  the  authors  represent  as  actual  results  of  investigation  in  their  special 
lines  and  what  they  add  thereto  regarding  '  general  problems.' 


76  THE  THEORY  OF  EVOLUTION 

On  the  other  hand  it  is  probable — in  some  cases  very 
probable— that  by  adaptation  to  varied  environments 
a  type  which  has  once  appeared  branches  off  into  divi- 
sions of  varied  appearance — as  with  the  Lepidophyton 
of  the  Carboniferous  period  for  example.  We  must 
therefore  accustom  ourselves,  with  plants  as  with  the 
animals,  to  speak  rather  of  a  c  transformation '  and 
alteration  of  form  than  of  an  actual  higher  evolution.1 

1  '  Higher  evolution/  in  the  strictest  sense  of  the  words,  would  be  correct 
if  (1)  an  objectively  based  division  into  higher  (more  perfect)  and  lower 
(more  imperfect)  grades  of  organization  of  the  animal  and  plant  kingdoms 
be  accepted,  and  (2)  if  such  a  higher  grade  has  been  formed  from  such  a 
lower  one.  The  second  premiss  we  must  dispute,  the  first  we  will  discuss 
hereafter. 


1 


SECTION  II. 

THE    EXPLANATORY    DOMAIN    OF    THE    HYPOTHESIS 
OF    EVOLUTION. 

CHAPTEK  I. 

INTRODUCTION. 

ACCORDING  to  what  we  have  so  far  stated  in  connection 
with  palaeontology  the  object  of  an  evolutionary  or 
transformation  hypothesis  is  fairly  well  defined. 

In  the  first  place  we  have  to  inquire,  by  observa- 
tion of,  and  experiment  with,  the  organisms  of  to-day, 
whether  they  are  generally  capable  of  transformation, 
what  causes  are  thereby  involved,  and  of  what  kind 
are  the  changes  ascertained. 

Thereby  we  arrive  at  the  first  and  entirely  indispen- 
sable basis  of  any  attempt  whatever  at  scientific  ex- 
planation through  observation.  The  second  part  of  the 
task  involved  would  be  to  imagine  the  same  causes  as 
effective  in  the  past,  alone  or  in  connection  with  other 
influences  of  similar  kind,  and  then  to  compare  the 
chronologically  successive  organisms  of  ascertainable 
form  and  structural  conditions  with  those  still  subject 
to  observation.  If  both  show  the  same  peculiarities, 
then  we  may  conclude  with  perfect  right  that  the  modi- 
fications of  the  primeval  animals  and  plants  were  really 
brought  about  by  those  causes  or,  better  expressed, 


78  THE  THEOKY  OF  EVOLUTION 

were  induced  by  them.  If  the  changes  of  form  of  the 
fossils  remain  within  the  limits  of  those  alterations 
which  we  at  present  observe  in  the  recent  organisms, 
or  can,  with  great  probability,  deduce  from  them,  then 
are  we  certain  that  our  explanation  is  correct.  If  they 
extend  farther,  we  must  inquire  whether  an  increase 
in  the  intensity  and  the  duration  of  that  influence  may 
not  explain  the  great  scope  of  the  deviations.  The 
certainty  of  our  deductions  certainly  is  decreased 
thereby.  How  far  the  application  of  these  principles 
may  be  carried  is  not,  however,  left  open  to  choice 
which  might  be  satisfied  with  a  mere  glimmer  of  possi- 
bility and  probability :  we  must  act  within  the  limits 
set  by  Nature  and  by  Science,  regarding  which  we  have 
already  said  what  is  needful  when  discussing  the  results 
of  palseontological  research. 

This  truly  scientific  standpoint  is  that  assumed 
by  many  eminent  palaeontologists,  such  as  Neumayr, 
Waagen,  Zittel,  Koken,  Steinmann,  Deperet,  Kerner, 
Marilaun,  Keinke,  and  Wasmann. 

We  believe,  however,  that  in  many  cases,  especially 
in  advanced  '  reading  circles/  such  a  standpoint  is  re- 
garded as  simply  '  naive  '  :  one  is  accustomed  there 
to  see  quite  other  and  deeper-seated  questions  treated 
after  a  certain  '  dogmatic  method/  in  books  on  evolu- 
tional history,  which  commence  with  these  purely 
scientific  problems  and  proceed  to  the  most  subtle 
questions  of  world-wide  breadth  (Weltanschauung). 
Why  we  do  not  do  that,  we  will  explain  as  follows. 
In  the  first  place,  a  word  on  the  so-called  '  palseonto- 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS         79 

logical  methods/  This  is  certainly  that  method  which 
adheres  to  the  historical  development  of  the  entire 
evolutional  problem,  and  therefore  also  that  which 
repeats  the  original  thoughts  and  permits  the  newly 
introduced  extensions  thereof  to  be  determined.  This 
was  the  method  adopted  by  an  eminent  palaeontologist 
— Ch.  Deperet — in  his  work  so  frequently  mentioned, 
and  the  honourable  reception  which  the  book  also 
experienced  among  German  savants l  shows  that  no 
one  found  any  objection  to  the  plan  adopted. 

This,  however,  does  not  imply  that  palaeontology 
is  alone  called  upon  to  finally  determine  the  limits  of 
transformation.  Thus  the  possibility  of  the  descent 
of  one  plant  type  from  another,  despite  the  perfectly 
negative  results  of  palaeontology,  is  by  no  means  dis- 
proved. In  many  cases  a  decision  cannot  be  arrived 
at  by  the  study  of  fossils  alone  because,  for  instance, 
the  petrifactions  of  the  pre-Cambrian  formation — even 
if  they  existed  in  larger  numbers — are  in  any  case 
shattered  or  destroyed,  and  indubitable  plant  remains 
are  not  so  far  known  from  pre-Silurian  formations. 
Under  these  circumstances  what  can  be  said  regarding 
the  earlier  history  of  the  Ferns  or  the  Trilobites  ?  It 
will,  however,  well  be  conceded  that  it  is  inadmissible  to 
speak  of  and  appreciate  only  the  favourable  side  of  the 
results  of  palseontological  research — viz.  the  abundant 
evidence  in  favour  of  manifold  new  forms — and  to  be 
silent  regarding  the  lack  of  any  probable  tangible 

1  The  book  was  very  favourably  spoken  of  by  Freeh,  Koken,  Steinmann, 
R.  Hoernes  and  other  paleontologists. 


80  THE  THEORY  OF  EVOLUTION 

evidence  of  the  transition  of  one  family  into  another, 
or  one  class  into  another,  both  in  the  animal  and  plant 
kingdoms.  Both  must  be  considered  in  the  same  way, 
unless  the  other  indices  for  the  evolution  of  organisms — 
comparative  anatomy,  embryology,  animal  and  plant 
geography,  etc. — lead  to  such  strong  indirect  proof 
that  the  negative  results  of  palaeontology  in  separate 
cases,  or  even  generally,  may  be  ignored.  In  this 
case  the  theory  or  hypothesis  could  really  serve  as 
an  explanation  of  an  occurrence  without  the  occurrence 
concerned  being  a  support  to  the  hypothesis.1 

Then,  for  example,  the  conclusion  that,  despite 
everything,  a  definite  class  must  have  been  derived 
from  another,  could,  considered  purely  theoretically, 
become  an  actual  scientific  postulate. 

The  '  scientific  postulates  ' — here  the  theory  of  evolu- 
tion— we  meet  with  now  very  often  in  contemporary 
literature.  Many  of  these  we  cannot  at  all  recognize 
as  such,  since  a  condition  absolutely  essential  for  the 
statement  of  a  postulate  is  left  out  of  consideration. 
For  instance,  no  trouble  is  taken  at  the  outset  to  ascer- 

1  Only  in  this  sense  is  Naegeli's  expression  correct  :  '  It  was  not  my 
intention  to  discuss  all  branches  of  the  doctrine  of  descent  .  .  .  Therefore 
the  otherwise  generally  treated  theme  of  geographical  extension  and  the 
palaiontological  evidence  have  been  almost  entirely  neglected  by  me, 
because  the  existing  demonstrated  facts  show  themselves  to  be  of  manifold 
significance,  and  because  their  explanation  may  be  much  rather  expected 
by  means  of  a  correct  theory  than  that  they  should  contribute  appreciably 
to  the  foundation  of  one.'  (Meclianiscli-pliysiolog.  Theorie  der  Abstam- 
mungslehre,  Munich  and  Leipzig,  1884,  v.).  Naegeli  in  point  of  fact  pro- 
ceeded in  the  said  work  on  purely  a  priori  lines,  since  what  '  is  '  he 
spoke  of  as  '  becomes,'  expressing  actual  facts  connected  with  the  present 
organisms  in  evolutional  historical  fashion. 


DOMAIN  OF  EVOLUTIONAKY  HYPOTHESIS       81 

tain  whether  the  facts  concerned  really  come  within 
that  category,  from  which  alone  the  basis  of  an  evolu- 
tionary hypothesis  can  be  formed.  An  example  in 
another  direction  will  explain  what  we  mean.  Let  it 
for  instance  be  conceded  that  the  physicists  justifiably 
claim  the  existence  of  ether  and  that  of  definite 
vibrations  of  its  smallest  molecules  because  thereby 
they  obtain  a  satisfactory  conception  of  the  phenomena 
of  light,  electricity,  etc. ;  therefore  it  is  scientifically 
perfectly  justifiable  to  employ  the  hypothesis  of  the 
ether  experimentally  also  to  account  for  other  natural 
processes,  provided  of  course  that  the  new  batch  of 
facts  requiring  explanation  can  be  comparable  with 
the  phenomena  of  light  and  electricity. 

But  no  one  could  seriously  attempt  to  use  the  ether 
hypothesis  in  order,  say,  to  explain  consciousness, 
memory,  and  the  will,  since  consciousness  by  its  entire 
nature  has  absolutely  nothing  to  do  with  a  material 
state  of  vibration.  The  basis  of  such  an  attempt  could 
be  formulated  in  the  following  way :  f  Since,  by  the 
recognition  of  a  material  ether  and  of  definite  vibra- 
tions of  its  molecules,  we  have  received  an  acceptable 
idea  of  light,  the  rapidity  of  its  transmission,  refrac- 
tion, etc.,  therefore  it  is  a  scientific  postulate  that  there 
be  recognized  also  consciousness,  and  action — in  short 
the  said  capacities — as  ethereal  vibrations,  even  though 
all  possibility  is  lacking  of  saying  how  it  is  done/ 

Unfortunately  the  formulating  of  many  evolutional 
'  postulates  '  is  similarly  framed  ! 

It  is  a  quite  inadmissible  procedure  to  put  forward 


82  THE  THEORY  OF  EVOLUTION 

things  and  processes  in  the  explanatory  formula  of  an 
evolutionary  hypothesis  as  the  postulate  of  the  same, 
when  such  things  or  processes  cannot  be  recognized  in 
their  entire  nature  as  the  results  of  an  evolutionary 
process.  That  would  be  the  case  if,  for  example,  in 
the  whole  of  our  experience  of  the  accessible  world 
absolutely  nothing  could  be  found  which  reasonably 
could  be  regarded  as  a  foundation,  as  an  undeveloped 
'  latent '  form — in  short,  as  a  beginning  of  that  which 
it  is  desired  to  explain,  since  '  evolution/  in  itself, 
signifies  development  and  extension  of  a  thing  or  con- 
dition which  at  least  can  be  suggested  -as  existent.  If 
two  things — of  which  the  one  has  the  perfection  or 
capacity  under  consideration,  the  other  possessing 
neither  even  as  a  commencement — exist  together,  these 
may  have  manifold  relations  to  each  other  and  naturally 
may  affect  each  other,  but  through  '  evolution '  they 
have  no  connection. 


CHAPTER  II. 

LIMITATION    OF    THE    EXPLANATORY     DOMAIN      OF     THE 
EVOLUTIONARY  HYPOTHESIS. 

Preliminary  Observation. 

THE  opinion  is  generally  held  that  the  natural  objects 
which  surround  us  may,  in  the  first  place,  be  divided 
into  two  great  and  quite  different  groups — the  animate 
and  inanimate.  The  animate,  again,  are  divided  into  the 
so-called  animals  and  the  plants,  and  these  are  treated  as 
separate  branches  of  natural  science.  The  animal  king- 
dom and  that  of  the  plants  are  again  divided  by  systems, 
agreeing  in  their  main  features,  into  stocks,  classes, 
orders,  families,  genera,  species,  and  sub-species,  etc. 

It  is  therefore  indubitable  that,  for  the  acceptance 
of  such  a  threefold  division  in  the  things  themselves, 
some  sort  of  starting-point  must  exist,  otherwise  it 
would  have  been  impossible  to  establish  associated 
but  strictly  separated  scientific  branches,  since  the 
definition  of  those  branches  is  effected  according  to 
the  difference  of  their  objects.1 

1  It  can  well  be  said  that  most  students  of  nature,  in  such  division  of 
the  natural  objects  into  separated  groups,  perceive  the  expression  of  actual 
relationship.  Otherwise  there  could  not  be  understood  the  standpoint  of 
the  chemist  and  physician  with  regard  to  *  pure '  biological  questions,  and 
that  of  the  physiologist  and  biologist  with  regard  to  '  pure  '  chemico- 
physical  ones.  The  physician  considers,  because  he  leaves  the  construction 
and  activity  of  organisms  to  the  biologist  and  physiologist,  that  he  is 
thereby  limited  in  his  particular  domain,  and  vice  versa  the  students  of  the 
organic  branches  have  their  own  methods  and  domain  of  investigation. 

G  2 


84  THE   THEORY  OF  EVOLUTION 

According  to  many  evolutional  theorists  these 
contrasts  between  the  organic  and  the  inorganic  (animate 
and  inanimate),  between  animals  and  plants,  between 
families  and  classes  within  the  same  kingdom,  should 
not  be  of  such  a  kind  as  to  be  inexplicable  by  '  evolu- 
tion/ The  acceptance  of  a  genetic  connection  is  indeed 
a  '  postulate  of  the  evolutionary  doctrine/  This  we 
must  contest,  since  there  are  lacking — at  least  so  far  as 
the  origin  of  life  from  the  inorganic  world  and  the 
evolution  of  animals  from  plants  are  concerned — all 
the  conditions  for  the  acceptance  of  a  '  postulate/ 

§  1.  We  are  not  justified  in  regarding  the  origin  of 
organisms  upon  our  Earth  as  the  result  of  an 
evolutionary  process. 

It  is  no  part  of  our  task  to  consider  here  all  the 
attempts  which  have  ever  been  made  to  explain  the 
appearance  of  life  upon  our  planet.  Fechner  and 
W.  Preyer,  for  instance,  accept  the  priority  of  life  and 
deduce  the  inorganic  from  the  organic.  According  to 
them  the  lifeless  bodies  were  '  the  signs  of  the  dead 
primeval  gigantic  organisms,  whose  breath  perhaps 
was  glowing  iron  vapour,  their  blood  molten  metal,  and 
their  food  perhaps  the  meteorites/ 

Several  eminent  physicists — HelmLolz,  W.  Thomson 
(Lord  Kelvin),  and  most  recently  Svante  Arrhenius— 
represent  the  '  opinion  '  that  organisms  have  ever  been 
associated  with  the  inorganic  material,  and,  pervading 
the  universe,  spread  the  germs  of  life  wherever  a  world 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS       85 

anywhere  became  capable  of  providing  a  habitat  for 
organic  existence.1 

This  idea  owes  its  origin  to  the  '  impossibility  that 
lifeless  material  can  pass  into  living/  3  The  investiga- 
tors named  do  not  therefore  rank  with  our  opponents  : 
their  opinion  implies  rather  '  a  fundamental  difference 
between  living  and  inorganic  substance  and  a  duality 
in  infinitum.' 3 

Such  attempts  at  explanation  have  naturally  not 
met  with  much  approbation  because  they  belong  to  the 
'  merry  realm  of  speculation '  and  are  absolutely 
beyond  proof. 

Now  and  again  the  belief  arises  in  the  doctrine  of 
'  spontaneous  generation/  the  most  acceptable  attempt 
at  explanation  of  the  origin  of  life  on  our  planet.  This 
implies  the  spontaneous  generation  of  living  bodies 
(organisms)  from  the  ordinary  (inorganic)  materials 
as  the  effect  of  ordinary  chemical  and  physical  powers, 
either  under  special  or  also  under  the  conditions  ruling 
at  the  present  time.4  As  a  rule  '  special '  environmental 
conditions  are  demanded  which  do  not  now  present  them- 
selves, but  no  details  of  such  specializations  are  given. 

1  Reinke  :    Die  Welt  als  Tat,  Berlin,  1905,  p.  344.     See  also  E.  v.  Hart- 
mann :  Das  Problem  des  Lebens,  Bad  Sachsa  i/Harz,  1906,  p.  178 ;   and 
H.  Muckermann  :  Grundriss  der  Biologic,  I,  Freiburg,  1909,  p.  144. 

2  0.  Hertwig  :  Attg.  Biologic,  p.  272. 

3  Reinke  :  Die  Welt  als  Tat,  Berlin,  1905,  p.  345. 

4  According  to  Naegeli  (Mechan.-Physiol.  TheoriederAbstammungslehre, 
87)  this  generation  occurs  in  the  '  warmer  seasons '  even  to-day  and  in 
our  own  regions,  principally,  however,  '  in  the  warmer  climates,  and  in  the 
old  primeval  time  after  the  cooling  of  the  earth  down  to  breeding  heat.' 
Usually  the  possibility  of  spontaneous  generation  is  only  attributed  to  the 
earliest  times. 


86  THE  THEORY  OF  EVOLUTION 

Such  an  origin  of  organic  life  must  be  denied  in 
the  name  of  Science,  because 

(1)  Between  organisms  and  inorganic  material  there 
is  an  essential  difference,  so  that  the  inorganic 
material  cannot  develop  itself  into  an  organism. 

For  the  comprehension  of  our  argument  the  mean- 
ing of  the  words  (  organism '  and  e  life '  must  be 
examined  more  closely.  The  simplest  and  most  general 
definition  which  is  afforded  by  modern  biologists  is  as 
follows  : 

An  organism  is  essentially  a  whole   composed 
of  material  and  functionally  varied  parts. 

Both  elements  of  the  signification — manif  oldness  and 
unity — are  clearly  expressed  in  the  word  '  organism/ 
The  ending  '  ism '  points  to  a  collection  of  organs. 
'  Organ  '  is  a  tool  for  a  denned  service  :  all  tools  together 
form  the  one  whole. 

The  peculiar  way  in  which  this  whole  is  in  itself 
active  is  termed  '  life/  It  can  be  briefly  denned  as 
1  the  definite  co-operation  of  all  the  limbs  (parts)  deter- 
mined by  constant  consideration  for  the  whole/  So 
comprehended  this  definition  suits  all  natural  bodies 
which  are  usually  considered  as  living,1  even  the  simplest 

1  There  are  other  and  very  good  definitions  of  *  Life.'  Scholastic 
philosophy  particularly  has  very  thoroughly  treated  the  doctrine  of  life. 
Since,  however,  we  have  desired  to  touch  upon  the  problem  of  life  only  in 
so  far  as  is  necessary  for  a  critical  examination  of  its  origin — as  it  is  pre- 
sented by  many  modern  naturalists — we  may  content  ourselves  with 
brief  indications.  For  the  use  of  many  very  indefinite  expressions  we  must 
hold  the  naturalists  concerned  responsible. 


DOMAIN  OF  EVOLUTIONAKY  HYPOTHESIS      87 

which  we  so  far  know — the  cells — whether  they  be  indi- 
vidual and  independently  existing  beings  (monocellular), 
or  constituents  of  a  so-called  '  higher  '  organism.  Since 
for  the  first  time  Briicke  (1861)  has  demonstrated  the 
ultimate  morphological  and  physiological  units  of  which 
the  organs  in  animals  and  plants  consist — viz.  the  ( cells ' 
—to  be  an  aggregation  of  varied  kinds  of  parts  connected 
together  by  definite  laws,  the  organic  cells  have  also 
been  designated  as  organisms — elementary  organisms. 

This  term  is  very  unhappily  chosen,  since  a  liver 
cell  or  a  kidney  cell  cannot  be  termed  an  (  organism ' 
in  the  sense  of  an  independently  existing  and  active 
whole.1  Since,  however,  the  expression  has  become 
widely  spread,  and  used  especially  by  most  of  the 
defenders  of  spontaneous  generation  (Urzeugung),  we  will 
accept  it  for  the  time  being.  It  is  important  for  us  to 
remember  that  the  cell — that  is,  the  absolute  or  relative 
ultimate  unit  of  living  matter  itself — is  composed  of 
many  varied  elemental  parts  which,  like  the  organs  in 
a  higher  organism,  co-operate  in  the  vital  process.3 
If,  therefore — precisely  because  the  cell  consists  of 
many  varied  and  co-operating  parts — it  has  been  termed 
an  organism,  that  then  is  a  proof  that  our  definition  is 
accepted  by  the  biology  of  to-day.  We  can,  therefore, 
proceed  upon  that  basis. 

In  the  definition  of  '  life  '  we  spoke  of  the  '  definite 
co-operation  of  all  the  parts  determined  by  constant 

1  See  E.  Wasmann  :  Die  moderne  Biologic  und  die  Entwcklungsffieoric; 
p.  190. 

2  O.  Hertwig :  Attgemeine  Biologie,  II. 


88  THE  THEORY  OF  EVOLUTION 

consideration  for  the  whole/  That  is  shown  by  the  fact 
that  each  part  works  for  all  others  precisely  as  it  does  for 
itself :  thus  the  lungs  breathe  for  all  the  tissues,  and 
digestion  is  effected  for  the  benefit  of  all,  and  so  on. 

Thereby  each  organ  is  itself  also  dependent  upon 
the  normal  execution  of  all  other  functions.  If  there 
arise  an  increase  of  activity  in  any  organ  that  is  so 
because  the  whole  or  some  particular  part  requires  it. 
In  short  there  is  shown  clearly  in  every  part  a  striving 
to  remain  preserved  in  conjunction  with  the  whole  or 
the  necessity  of  perishing  with  it. 

M.    Heidenheim !    very    beautifully    describes    this 

relation  of  the  separate  components  to  the  whole  :  '  In 

the  more  highly  organized  creatures  the  cells  present 

themselves  as  subordinate  parts  of  the  whole,  which 

have  lost  the  freedom  of  existence  and  of  action,   a 

condition  which  is  designated  by  H.   Spreuzer  as  an 

"  integration  "  of  the  individual,  because  it  has  become 

an  integral  part  of  the  whole.     In  connection  therewith 

there   is   the   extremely   varied   differentiation    of   the 

specifically  functional  cells.  ...  It  is  this  change  of 

constitution  which,  in  the  theoretical  sense,  confirms 

and  determines  the  dependent  relations  of  the  whole, 

the  integration  of  the  individual  and  the  subordination 

of  the  cells  to  the  position  of  mere  tools  which  serve  for 

the  vital  work— the  "  life."  ' 2 

1  Plasma    und    Zelle,  8th  volume   of    Handbuch    der  Anatomic  des 
Menschen,  published  by  Bardeleben,  Part  I,  Jena,  1907,  p.  29. 

2  Heidenheim   contests  in   this   work   with   powerful   arguments   the 
doctrine  that  a  complex  organism  is  a   cell  community  (Zellestaat) :   see 
particularly  p.  49. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS       89 

From  the  above  it  is  understood,  when  it  is  said  of 
the  organisms,  that  they  constitute  a  purpose  in  them- 
selves. Observation  indeed  shows  us  that  they  attain 
no  other  object  than  self-preservation  or  increase  in 
number  by  the  reproduction  of  like  beings.  We  see  the 
same  if  we  more  closely  observe  their  behaviour  towards 
inorganic  material  and  the  universally  effective  powers 
of  Nature.  The  organisms,  it  is  true,  are  thoroughly 
dependent  for  their  existence  on  the  chemico-physical 
powers  and  the  inorganic  materials,  but  their  relation 
to  these  is  so  regulated  that  they  utilize  and  profit  by 
such  influences  and  effects  as  are  consistent  with  their 
own  maintenance.1  Furthermore  the  living  bodies 
cannot  effect  any  material  work  at  all  independently 
of  the  material  and  the  peculiar  powers  which  accrue 
to  it  also  from  outside  ;  but  the  chemical  materials,  for 
example,  are  so  arranged,  and  in  their  activity  so  ruled, 
that  they  only  act  in  such  a  manner  and  at  such  a  time, 
how  and  when,  as  is  necessary  to  the  organism  for  its 
purposes. 

From  this  generally  conceded  dependence  upon  the 
use  of  material  energies  it  might  be  concluded  that  the 
organism,  after  utilizing  same,  must  come  to  a  stand- 
still ;  but  that  is  not  so.  The  living  body  obstinately 
maintains  itself  in  its  active  condition,  since  it  rejects 
the  exhausted  material  and  seeks  and  assimilates  a 
new  supply.  With  the  fresh  material  it  forms  highly 

1  Naturally,  however,  we  will  not  deny  that  all  organisms  can  bo 
destroyed  ;  they  are  not  absolute  existences.  The  purposeful  '  utilization  ' 
of  the  inorganic  materials  and  powers  is  evident  in  the  normal  life — that 
suffices  perfectly. 


90  THE  THEOKY  OF  EVOLUTION 

complex  and  highly  changeable  chemical  combinations 
and  thus  creates  new  springs  of  energy.  This  continuous 
exchange  of  material,  by  which  nothing  else  is  attained 
and  striven  for  than  the  self-maintenance  and  multipli- 
cation of  its  individuality,  shows  itself  in  the  most 
striking  way  in  the  external  appearance  and  is  therefore 
utilized  by  many  investigators  in  their  definitions. 
Thus,  for  instance,  0.  Hertwig  states  :  f  Life  (using  a 
general  expression)  displays  itself  therein  that  the  cell, 
by  virtue  of  its  own  organization  and  under  external 
influences,  suffers  constant  changes  and  develops  powers 
by  which  its  organic  substance,  on  the  one  hand, 
under  definite  expressions  of  energy  is  destroyed,  and, 
on  the  other,  is  again  renewed/  l 

All  that  has  so  far  been  stated  shows  that  the 
organisms  possess  a  power  of  their  own  to  strive  to 
attain  certain  purposes  and  that  they  only  convert 
and  use  inorganic  material  in  their  own  interest. 

This  conception  is  entertained  also  in  one  or  another 
form  by  the  majority  of  modern  biologists,2  as,  for 
instance,  by  Cl.  Bernard,3  0.  Hertwig,4  K.  E.  v.  Baer, 

1  Attg&meine,  Biologie,  p.  65. 

2  Christian  philosophy  has  always  taught  this  and  has  never  accepted 
that  enigmatical  '  vital  force  '  which  should  be  a  particular  form  of  energy, 
but  has  conceded  to  the  organism  a  substantial  principle  as  having  a 
purposeful  striving  power. 

3  Lemons  sur  les  Phenomenes  de  la  Vie-,  I,  Paris,  1879,  p.  51.     '  The  vital 
force  (here  =  cause  of  unit  direction)  directs  phenomena  which  it  does  not 
produce  ;     the   physical   agents  produce  phenomena  which  they  do  not 
direct.'    II,  p.  524  :  '  The  ultimate  element  of  the  phenomenon  is  physical, 
the  arrangement  is  vital.' 

4  Allgemeine  Biologic,  pp.  16,    18,    65.     The   same  :    Der   Kampf  urn 
Kernfragen  der  Entwicklungs-  und  Vererbungslehre,  Jena,  1900,  pp.  75,  80. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS        91 

Heidenheim,  Pfeffer,1  Bunge,3  Reinke,3  H.  Driesch,4 
Strasburger,5  and  practically  and  actually  by  all  botanists 
and  zoologists,  even  those  who  theoretically  still  regard 
life  as  a  chemico-physical  process  of  peculiar  complexity. 

Conclusions  from  the  above. 

1.  '  Life/  in  the  next  place,  is  understood  quite 
generally  by  modern  naturalists  as  a  peculiar  mode  of 
activity  which  we  only  find  in  the  so-called  organisms, 
i.e.  in  systems  which  exteriorly  are  contained  within 
themselves  and  which  consist  of  chemically  varied  and 
structurally  differentiated  parts.  It  consists  essentially 
therein  that  all  parts  of  such  an  organism  naturally 
act  together  or  are  active  as  instruments  in  the  service 
of  the  whole  and  on  their  own  initiative. 

That  there  are  natural  bodies  which  display  the 
activity  described,  in  contrast  to  others  in  which  it 
does  not  exist,0  is,  for  01.  Bernard,  '  a  fact  to  be 
no  longer  disputed ' ;  for  0.  Hertwig,  '  a  fact  and 

1  Pfeffer's  decision  in  the  Pfianzenphysiologie,  Leipzig,  1897  and  1904, 
we  will  give  hereafter  under  the  discussion  on  stimuli. 

2  Lehrbuch  der  Physiologic  des  Menschen,  II,  Leipzig,  1905,  p.  7.     '  In 
the  activity,  therein  lies  the  enigma  of  life.' 

3  Einleitung  in  die  Theoretische  Biologie,  Berlin,  1901,  sections  3  and  4  ; 
also  Die  Weltals  Tat,  Berlin,  1905,  chaps,  xxii.  and  xxiii. 

4  We  will  treat  later  on  of  Driesch  in  detail. 

5  The  well-known  Lehrbuch  der  Botanik  fur  Hochschulen  maintains  this 
opinion  and  establishes  it  excellently. 

6  01.  Bernard  (Lemons  sur  les  Phenomenes  de  la  Vie,  p.  50)  calls  the 
'  wonderful  subordination  and  the  harmonious  co-operation  of  the  vital 
activities  '  a  fact  to  be  no  longer  disputed   ('  le  mot  importe  peu,  il  suffit 
que  la  realite  du  fait  ne  soit  pas  discutable').     O.  Hertwig  (Kampf  um 
Kernfragen,  etc.,  p.   80) :    '  That  the  living  substance  ...  in  accordance 
therewith  (i.e.  with  its  organization),  develops  peculiar  ways  of  working,  is, 
in  my  eyes,  a  fact  and  no  mystical  conception  as  Verworn  regards  it.' 


92  THE  THEORY  OF  EVOLUTION 

no  mystical  conception  as  Verworn  regards  it/1 
In  an  organism  all  parts  thus  show  '  final  change 
relations  '  (finale  Wechselbeziehungeri)  which  are  lacking 
in  inorganic  material.2 

2.  The  result  which  is  attained  in  all  cases  by  this 
co-operation  is  exclusively  the  maintenance  and  repro- 
duction of  the  organism  itself.  This  result  is  rendered 
possible  by  the  capacity  of  the  organisms  to  utilize  and 
assimilate  the  inorganic  material  whenever  it  is  required. 
This  capacity  is  shown,  for  instance,  in  the  purposeful 
selection  of  the  material  which  normally  is  taken  up, 
in  the  exclusion  of  poisonous  matter  3  and  the  ejection 

1  Verworn  maintains — it  is  true,  casually — in  Allgemeine  Physiologic, 
Jena,  1901,  the  essential  similarity  of  the  vital  processes  and  the  chemico- 
physical   ones,    but   he   thinks   in   the   next   place   only   of   the    '  bodily 
phenomena  of  life  '  (p.  7) ;   the  physical  form  a  problem  of  their  own.     On 
p.  106  he  concedes  '  that  the  living  substance  cannot  be  associated  with  the 
chemical  without  being  killed.'     Then  is  the  life  departed  !     The  most 
superficial  conception,   at  least  in  some  places,  we  have  found  in   the 
otherwise  excellent  work  Traite  d'Histologie  (published  by  H.  Prenant, 
Bourn,  and  Maillard),  I,  4.     Prenant  must  have  had  here  an  opponent  in 
view,  who  has  maintained  all  sorts  of  nonsense.     On  p.  18  he  himself 
describes  the  peculiarity  of  life  as  the  struggle  for  the  maintenance  of  a 
type  associated  with  constant  protoplasmic  change. 

2  C.  v.  Hartmann  :  Das  Problem  des  Lebens,  p.  206.     In  cell-like  forms  of 
inorganic  nature  '  each  part  is  as  it  is,  and  must  be,  according  to  effective 
molecular  local  forces,  but  it  is  not  a  serviceable  member  of  a  higher  whole. 
Between  the  parts  there  occur  certainly  causal,  physico-chemical  changes, 
but  no  final  change  relations  by  which  each  part  serves  all  the  others  and 
all  of  them  together  minister  to  the  whole.' 

s  G.  v.  Bunge :  Lehrbuch  der  Phi/siologie  d.  Menschen,  II,  p.  5.  '  We 
know  that  the  epithelial  cells  of  the  bowel  never  permit  the  entrance  of  a 
\vhole  series  of  poisons  although  these  in  the  fluids  of  the  stomach  and 
bowel  are  quite  easily  dissolved.  [Thus  the  mechanico-chemical  conditions 
for  absorption  are  determined  ! — Remark  by  author.]  We  know  even, 
that  if  we  inject  these  poisons  direct  into  the  blood  they  become,  on  the 
other  hand,  ejected  through  the  walls  of  the  bowel.'  For  other  very 
strong  proofs  of  the  utilization  of  the  natural  forces,  see  the  same,  p.  3. 


DOMAIN  OF  EVOLUTIONAKY  HYPOTHESIS      93 

of  the  matter  exhausted  by  the  organism  itself,  in  the 
increase  and  diminution  of  the  functions  proper  to  the 
whole  or  to  the  parts,  with  the  consequent  morpho- 
logical changes  of  form — the  so-called  '  adaptations/ 

A  result  or  an  object  that  under  certain  circum- 
stances may  be  enforced  through  adaptations,  is 
obviously  one  striven  for,  one  with  a  purpose  :  the 
preservation  of  the  organism  is  thus  the  peculiar 
purpose  of  life  ;  or  in  other  words,  the  organism  is  at 
once  the  bearer  and  the  purpose  of  life.1  It  is  the 
bearer  because  the  possibility  of  life  depends  upon 
its  organization ;  and  it  is  the  purpose  because 
nothing  else  is  attained  and  striven  for  than  its 
preservation — of  its  individual  self  for  a  period, 
and  of  its  species,  so  far  as  in  it  lies,  for  ever. 

That,  likewise,  must  be  conceded  by  biologists  and 
physiologists,  since  it  is  never  a  question  of  another 
result  or  purpose  when  the  subject  treated  of  in 
the  textbooks  is  the  vital  properties  of  organisms 3 
(or  the  cell,  which  is  regarded  as  the  simplest  form  of 
organism). 

3.  It  is  granted  by  investigators  that  all  material 
products  of  labour  which  are  observed  in  an  organism 
result  from  utilization  of  purely  inorganic  energies. 
It  is,  however,  equally  certain  that  all  material  activity 
is  directed  to  a  single  end — the  preservation  of  the  whole. 

1  Here  it  is  a  question  of  the  so-called  '  inner  '  (i.e.  inherent)  purpose  in 
things  which  is  striven  for  by  them  directly  (finis  internus}.     The  question, 
Why  organisms  exist  ?  would  be  one  concerning  their  external  purpose 
(finis  externus). 

2  See,  for  instance,  Bl  O.  Hertwig  :    Allgemeine  Biologic,  p.  65. 


94  THE  THEORY  OF  EVOLUTION 

Cl.  Bernard  describes  in  a  classical  fashion  this 
double  side  of  vital  activity  :  '  La  force  vitale  dirige  des 
phenomenes,  qu'elle  ne  produit  pas,  les  agents  physiques 
produisent  des  phenomenes  qu'ils  ne  dirigent  pas/  l 

4.  By  these  words  there  is  a  new  deduction  expressed, 
viz.  that  the  conduct  and  constant  regulation  ('  direc- 
tion ')  of  the  inorganic  powers  must  have  a  special 
course  of  their  own.  Cl.  Bernard  uses  for  this  the 
words  '  force  vital '  (vital  force),  but  does  not  think  of 
embracing  therein  any  of  the  other  known  forms  of 
energy  of  equal  power,  but  can  only  identify  them  with 
the  organizations  themselves. 

J.  Reinke  calls  the  cause  (or  causes)  of  the 
purposeful  direction  of  the  purely  material  energies 
'  Dominants/  and  explains  the  term  as  follows  :  '  In 
the  organisms  work  is  done  by  energy — by  the 
Dominants  the  work  to  be  done  by  energy  is  deter- 
mined/ £  '  Their  existence  is  therefore  a  necessity, 
because  without  them  only  purposeless  forces,  first 
hand  (erster  Hand),  would  be  active  ;  we  see,  how- 
ever, in  point  of  fact,  that  both  the  chemical  and 
the  constructive  processes  in  plants  and  animals 
proceed  purposefully  and  in  unison/  3 

H.  Driesch  demands  the  acceptance  of  '  Entelechia/ 
The  word  (  Entelechia  '  signifies  the  inner  conformity 
of  living  bodies  ;  in  a  wider  sense, '  the  actual,  elementary 

1  Cl.  Bernard :  Lemons  sur  les  Phenomenes  de  la  Vie,  I,   p.   51.     Vital 
force  directs  phenomena  which  it  does  not  produce  ;  the  physical  agents 
produce  phenomena  which  they  do  not  direct. 

2  Die  Welt  als  Tat,  p.  292. 

3  Ibid. 


DOMAIN  OF  EVOLUTIONAKY  HYPOTHESIS       95 

natural  agency  which  expresses  itself  in  them/  '  Ente- 
lechia  utilizes  the  factors  of  the  inorganic  in  order 
to  produce  that  which  is  suitable  to  the  particular 
species  concerned  and  to  regulate  its  preservation/  l 
'  Entelechia  is  that  something  which  carries  its 

purpose  in  itself  (o  e-^eu  ev  eavrw  TO  reXo?)/  2 

Since  we  are  not  idealists,  the  '  Dominants '  and 
'  Entelechia '  do  not  signify  for  us  any  symbols  and 
abstractions  (Reinke),  but  actual  things  which  we, 
with  the  philosophy  of  past  ages,  call  the  '  soul/  As 
evidence  there  suffices,  however,  the  confession  that 
in  the  activity  of  the  organism  there  asserts  itself  a 
principle  which  stands  above  inorganic  matter  and 
forces. 

An  organism  is  thus  a  natural  body  which  by  virtue 
of  a  directive  and  regulating  principle  conducts  material 
activities  and  products  of  such  on  a  plan  and  regulates 
these  actively  and  purposefully  to  an  end  which  is 
inherent  in  the  organism  itself. 

5.  Since  the  inorganic  material,  left  to  itself,  never 
betrays  the  trace  of  a  tendency  to  form  such  a  system  in 
which  the  separate  parts  are  only  instruments,  there 
is,  between  organisms  and  combinations  of  inorganic 

1  Der  Vitalismus  als  Geschichte  und  als  Lehre,  Leipzig,  1905,  pp.  242,  246. 
He  treats  this  subject  very  fully  in  the  Philosophic  des  Organischen,  II, 
p.  137.     H.  Driesch  appears  to  have  made  the  study  of  life  his  particular 
task.     His  evidences  of  the  autonomy  of  life  in  his  many  works  and 
writings  are  executed  with   a  marvellous   expenditure   of   thought,  but 
are  inaccessible  to  ordinary  men  through  the  many  new  terms  and  his 
mathematico-analytical  methods. 

2  Philosophic  des  Organischen,  I,  p.  145.     The  word  is  borrowed  from 
the  writings  of  Aristotle. 


96  THE  THEORY  OF  EVOLUTION 

matter  and  their  mode  of  action,  a  fundamental 
elementary  difference. 

A  fundamental  difference  cannot  be  bridged  over 
by  evolution,  which  by  its  meaning  indicates  a  need 
of  a  starting-point  as  basis  for  a  perfection  to  be 
developed.  Therefore  spontaneous  generation  in  the 
usual  sense  of  the  term  is  excluded.  The  inorganic 
materials  can,  taking  them  absolutely,  perhaps  form 
those  chemical  combinations  which  appear  in  the 
organism ;  but  they  cannot,  by  themselves  (sponte), 
adopt  a  direction  and  a  higher  purpose,  nor  pro- 
duce Dominants  and  Entelechia,  because  these  stand 
above  them  and  have  nothing  to  do  with  material 
energy. 

We  have  thus,  in  the  activity  of  living  bodies  and 
in  the  behaviour  of  non-organized  matter  left  to  itself, 
learnt  to  know  two  kinds  of  natural  phenomena,  both 
of  which  are  alike  elementary  (primary).  Elementary 
natural  processes  cannot  be  deduced  from  each  other  : 
there  can  be  no  question  of  bringing  living  organisms 
and  unvivified  matter  into  genetic  connection  by  evolu- 
tion. Everything  that  we  know  of  the  origin  of  the 
present-day  organisms  agrees  therefore  entirely  with 
this,  viz.  that  the  phrase  omne  vivum  ex  vivo  (and 
omnis  cellula  ex  cellula)  stands  unshaken — nay,  is  more 
firmly  established  than  ever. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS       97 

(2)  The  attempts  to  demonstrate  as  possible  a  genetic 
connection  between  vivified  and  non-vivified  matter, 
or  even  to  describe  the  course  of  the  process,  must 
be  regarded  as  perfectly  vain. 

It  is,  in  short,  clear  that  no  investigator  considers 
that  through  chemical  structures  of  the  most  complicated 
sort  there  can  be  explained  the  origin  of  a  new  substance 
or  of  a  directing  '  something '  that  stands  above  the 
properties  of  matter.  Although  this  '  something  '  may 
be  clearly  equally  effective  as  the  purely  energetical 
processes  in  the  organism,  and  therefore  formally 
demands  a  scientific  explanation,  it  is  only  too  often 
overlooked.  The  organism  itself  is  alone  regarded,  and 
it  is  believed  that  thereby  the  second  element  of  vital 
phenomena,  the  constant  purposeful  direction  of  the 
purely  chemico-physical  processes,  has  been  traced 
to  a  sufficient  cause.  But  that  is  not  the  case. 

(i)  No  organization,  which  is  regarded  only  as  a 
peculiar  chemico-physical  quality  or  structure  of 
inorganic  matter,  explains  life. 

The  term  '  organization/  as  it  is  particularly  used  by 
0.  Hertwig  and  Cl.  Bernard,  is,  in  point  of  fact,  a  purely 
biological  one,  and  means  '  the  albumen  bodies  which 
build  up  the  protoplasm  and  all  its  innumerable 
derivatives  .  .  .  and  stand  in  nearer  and  ordered  rela- 
tions to  each  other  and  constitute  the  being  of  the 
organism/  L  '  Organization  '  means,  thus,  '  ordered 

1  O.  Hertwig  :   Attgemeine  Biologie,  p.  16. 


98  THE  THEOBY  OF  EVOLUTION 

relations/  It  signifies  also,  even,  according  to  Hertwig — 
and  the  same  may  be  said  of  other  naturalists  who  come 
here  into  consideration1 — that  it  is  not  merely  by  the 
existence  of  a  definite  physical  aggregate  condition,  or 
by  a  stiff  internally  connected  mechanism,  as  is  the 
case  in  a  machine,  or  by  peculiar  chemical  combinations, 
that  life  can  be  explained.  That  the  phenomena  of 
life  can  be  referred  to  the  properties  of  the  liquid  aggre- 
gate condition  0.  Hertwig  denies  '  emphatically  '  and 
refers  in  that  connection  to  many  other  investigators.2 
The  '  structures/  however,  also  explain  nothing,  since 
all  the  coarser  structures  observed  in  cells — tissues, 
threads,  network  structures,  and  seed  structures- 
have  shown  themselves  long  since  to  be  temporary 
forms,  conditions  of  the  protoplasm,  or  the  morpho- 
logical expression  of  a  particular  function.  They  can 

1  Even  Prenant,  the  author  of  the  first  section  of  vol.  i.  of  the  Traite 
d* Histologie,  can  only  classify  the  combinations  of  matter  which  take  place 
in  protoplasm  according  to  their  purpose  and  their  vital  importance.      He 
defines  six  groups  —foodstuff,  reserve  and  excreted  products,  and  rigorously 
specialized  instruments,  e.g.  myelin,  chlorophyll,  haemoglobin — supporting 
material  and  active  material.     Not  a  word  of  chemico-physical  points  of 
view  which,  for  instance,  arise  in  connection  with  aggregate  conditions  or 
definite  molecular  groups.     He  introduces  this  grouping  by  the  words  : 
'  On  peut  cependant  [since  '  chemical  '  is  not  concerned],  etablir  une  classifi- 
cation biologique  parmi  les  differentes  substances  trouvees  dans  les  cellules ' 
(see  p.    10).    See  also  particularly  E.  B.  Wilson :    The  Cell  in   Develop- 
ment and  Inheritance,  New  York,  1900,  p.  316.     This  work  is  certainly  the 
best  that  has  been  written  on  general  biology.     Furthermore,  O.  Hertwig  : 
Allg.  Biologie,  p.  26  ;  E.  Wasmann  :  Moderne  Biologie,  chap.  iii. 

2  Allgemeine  Biologie,  p.  16 :  '  With  Naegeli  and  many  other  investigators 
we  share  the  conviction  that  the  complicated  phenomena  of  the  vital 
processes— before  all,   those  of   inheritance — are   not   explicable   by  the 
qualities  of  liquids  or  matter  in  solution.     Wiesner  is  justified,  therefore,  in 
terming  the  attempt  to  refer  the  peculiarities  of  the  living  substance  to 
qualities  of  liquids  a  surprising  one.' 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS        99 

be  permanently  together  in  different  cells  of  the  same 
organism  and  stand  obviously  in  the  closest  connection 
with  the  separative  function  of  the  separate  organs  ; 
they  may  arise  successively  in  one  and  the  same  cell, 
according  to  varied  functional  conditions — for  instance, 
times  of  rest  and  activity.  This  applies  also  to  the 
structure  of  the  nuclear  substance.1 

According  to  the  latest  views  of  the  study  of  the  cell 
we  cannot  speak  of  '  organs  '  of  the  cell  in  the  sense  of 
formations  permanently  existing  and  indispensable  for 
definite  objects  (e.g.  cell  division).  That  is  true  for 
the  cell  skin,  the  centrioli,  the  '  chemical  central-bodies/ 
the  nucleoli,  and  the  rest  of  the  included  constituents, 
and  even  for  the  nucleus.  It  is  no  longer  correct  to 
refer  to  the  nucleus,  in  the  definition  of  the  cell,  as  one 
of  the  equivalent  parts  of  the  rest  of  the  cell  contents. 
The  nucleus  does  not  appear  at  all  in  an  enclosed  bladder 
in  many  unicellular  organisms,  but  only  the  so-called 
nuclear  substance ;  during  each  cell  division  it  is 
perfectly  dissociated  individually,  but  it  is  not  essential 
that  it  has  a  definite  structure.  The  cell  is  therefore 
that  more  or  less  exclusive  and  independent  mass  of 
vivified  matter  in  which  alone  the  vital  functions 
are  exercised.  The  cell  assimilates,  the  cell  divides 
itself,  etc.,  the  nucleus  and  the  centrioli  being  only 
integral  constituents  of  the  total  mass.  Wilson 
expresses  this  as  follows :  e  A  minute  analysis  of 

1  St.  Maziarski :  Sur  les  changements  morphologiques  de  la  structure 
nucleaire  dans  les  cellules  glandulaires,  in  Archiv  fiir  Zellforschung,  IV, 
Leipzig,  1910.  p.  443. 

H  2 


100  THE  THEORY  OF  EVOLUTION 

the  various  parts  of  the  cell  leads  to  the  conclusion 
that  all  cell  organs,  whether  temporary  or  permanent, 
are  local  differentiations  of  a  common  structural 
basis/1 

Furthermore,  the  acceptance  of  submicroscopic 
structures,  for  instance,  in  the  sense  of  a  connected 
filamentary  structure  as  a  mechanical  basis  of  the 
vital  processes,  is  of  no  assistance,  since  there  cannot 
obviously  be  attributed  to  such  hypothetical  structures 
any  such  qualities,  as  for  instance,  of  rigid  '  mechanism ' 
structure,  from  which  the  actually  observed  new 
formation  and  transformation  of  the  so-called  cell 
organs  (centrioli,  nucleus,  filamentary  structures  in  the 
protoplasm)  could  not  result.  The  cell  clearly  disposes 
quite  freely  of  its  material,  it  builds  from  its  common 
basis  the  centrioli,  always  completes  its  nuclear 
substance,  forms  new  nucleoli  and  dissolves  all  this 
again  according  to  whether  it  requires  one  of  these 
organs  precisely  for  a  particular  office  or  not. 

Conclusion. — There  is  in  the  cell  no  rigid  mechanical 
structure  either  in  the  protoplasm  (cytoplasm)  or  in 
the  nucleus.  The  '  organization  '  is  in  fact  only  the 
purposeful  co-operation  of  all  constituents  of  the  cell 
contents  (regarded  as  elementary  organism)  or  the 
displayed  subordination  of  all  parts  in  the  service  of 
the  whole  shown  in  the  activity  of  the  cell ;  '  organiza- 
tion '  is  thus  in  the  meantime  a  purely  biological  term, 
i.e.  it  expresses  only  a  peculiarity  of  the  activity  of 

1  E.  B.  Wilson :   The  Cell,  p.  327. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      101 

the  organism,  not  a  chemical  formula  or  a  material, 
rigid,  mechanical  system. 

No  conceivable  organization  is  by  itself  a  sufficient 
cause  of  the  purposeful  direction  of  all  the  constituents 
of  an  organism  and  of  its  power,  at  first  hand,  for  the 
best  benefit  of  the  whole.  So  far  as  a  structure  is 
observed  in  any  way,  it  shows  itself  as  the  effect 
of  a  function.  The  functions  are  the  primary  factors, 
or  rather  the  whole  which  utilizes  material  matter  and 
energies  for  the  common  benefit. 

What,  furthermore,  does  the  expression  of  the 
'  chemist '-  (  This  particular  material  group  of  matter 
is  the  foundation  for  the  eye  ' — mean  ?  How  can  the 
tendency  to  development  which  makes  itself  quite 
evident  in  a  fertilized  egg  be  brought  under  a  structural 
formula  ?  What,  for  the  chemist,  is  '  growth  '  and  evo- 
lutional energy  ?  *  Is  a  chemical  formula  imaginable 
which  can  express  '  inheritance  '  ?  *  What  formula 
has  conscience,  and  what  structure  and  organization 
can  present  it  graphically  ?  All  that,  however,  belongs 
to  '  life/  and  should  be  explained. 

1  Reinke  :  Die  Welt  als  Tat,  p.  293. 

2  Bunge  well  expresses  this  (Lehrbuch  d.  Physiol.  d.  Menschen,  II) :  '  But 
we  can  perfect  the  aids  to  investigation  !  We  can  increase  the  powers 
of  the  microscope  !  The  cell,  which  appears  structureless  to-day,  will  show  a 
structure  to-morrow.  .  .  .  And  the  nucleus  also  is  no  longer  structureless. 
.  .  .  But — a  complex  structure  is  no  explanation  :    it  is  a  new  enigma. 
How  has  this  complex  structure  originated  ?     Will  it  perfectly  solve  the 
great    enigma,    the    greatest    of    all — the    enigma    of    inheritance — the 
inheritance  through  a  small  cell  ?  ' 


102  THE  THEORY  OF  EVOLUTION 

(ii)  The  attempts  to  present  the  process  of  evolution  in 
a  concrete  form  demonstrate  the  impossibility  of 
spontaneous  generation. 

(a)  The  attempt  of  Naegeli1  to  render  comprehen- 
sible the  origin  of  the  simplest  organisms  from  inorganic 
matter  must  be  regarded  as  a  complete  failure.  The 
'  being  originating  from  spontaneous  generation  '  must, 
according  to  him,  '  be  in  the  first  place  perfectly  simple  ' 
1  without  external  form  and  without  internal  members/ 
pure  albumen,  which  then  nourishes  itself.  That 
'  scarcely  merits  the  name  of  an  organism,  but  it 
may  be  the  commencement  of  a  series  which  leads  to 
an  organism/  '  Growth  and  reproduction  gradually 
acquire  by  inner  relations  greater  definition/  etc. 
In  this  way  '  gradually  all  qualities  of  the  monad  are 
newly  generated/ 

Shortly  stated,  the  entire  allegation  is  to  the  effect 
that  a  cell,  as  it  now  is,  is  first  analysed  and  then  again 
brought  together  piece  by  piece,  whereby  nourishment 
and  reproduction  gradually  come  in  as  firmly  established 
peculiarities.  The  first  really  living  being  that  we  know 
of  (according  to  Naegeli  the  '  monad  ')  '  must,  in  the 
organized  arrangement  of  its  parts,  be  already  far 
advanced  and  therefore  have  a  long  series  of  ancestors 
behind  it/  Certainly  !  That,  however,  which  existed 
before  the '  monad '  was  the  purely  hypothetical '  probien ' 
which,  if  they  lived,  must  also  have  had  that  organic 

1  Naegeli  :   Theorie  d.  Abstammungslehre,  pp.  83,  86. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      103 

arrangement  and  a  long  line  of  ancestors,  and,  if  they 
had  not  these,  did  not  live  at  all,  but  were  (  drops  of 
albumen  of  the  most  perfect  simplicity/  l 

(b)  The  hypothesis  recently  put  forward  by  Meresch- 
kowsky,3 of  the  two  kinds  of  plasma,  only  concerns  us 
here  in  so  far  that  it  also  tries  to  explain  spontaneous 
generation. 

As  claims,  '  which  unavoidably  must  be  made  for 
the  first  organisms/  Mereschkowsky  cites  minute  sub- 
microscopic  size,  absence  of  organization  (?),  capacity 
of  standing  high  temperatures,  of  living  without  oxygen, 
of  forming  albumen  and  carbo-hydrates  (starch  and 
sugar)  out  of  inorganic  matter,  and  great  resistance 
against  strong  salt  solutions  and  poisons.  All  this  we 
see,  so  he  continues,  demonstrated  in  the  bacteria. 
Therefore  they  must  have  been  the  first  organisms. 
It  may  be  that  the  bacteria  were  the  first  organisms, 
but  from  Mereschkowsky 's  statement  that  by  no  means 
follows.  But  since  these  original  beings  were  organisms 
—the  visible  organism  we  will  willingly  accept  as  non- 
present — and  sturdily  maintained,  nourished,  and  re- 
produced themselves,  they  were  consequently  perfect 
living  beings  with  an  organization  in  the  biological 
sense.  How,  however,  did  these  living  organisms  arise 
from  albumen — particularly  the  power  of  reproduction, 

1  Naegeli :   Theorie  d.  Abstammungslehre,  p.  86. 

2  Prof.    Dr.     C.    Mereschkowsky    (Bid.    Zentralbl.,     1910,   p.   278  : 
Theorie  der   zwei   Plasmaarten  als   Grundlage  der   Symbiogenesis,   einer 
neuen  Lehre  von  der  Entstehung  der  Organismen)  explains  the  origin  of 
all  higher  organisms  ^by  symbiosis  of  mycoplasma  and  amcebo plasma.     In 
a  general  way,  as  this 'doctrine  is  put  forward,  it  is  not  to  be  taken  seriously. 


104  THE  THEORY  OF  EVOLUTION 

this  stubborn  tendency  to  self-preservation  ?  These 
arose,  according  to  Mereschkowsky,  in  the  following 
way  :  As  gradually  the  conditions  for  the  formation 
of  new  mycoplasma  became  more  unfavourable  '  the 
albumen  began  to  decompose,  to  decay,  and  it  could 
no  longer  build  anew.  By  virtue  of  this  there  conse- 
quently disappeared  the  conditions  for  the  formation 
of  living  mycoplasma,  and  the  further  development  of 
life  could  only  proceed  on  the  principle  of  omne  vivum 
e  vivo.  There  arose  at  once  one  of  the  main  differentia- 
ting peculiarities  of  life— the  capacity  of  reproduction, 
i.e.  of  commencing  new  beings  from  living  parts  of  the 
old  ones,  since  only  such  particles  of  albumen  could 
flourish  which  possessed  this  faculty  ^  and  had  such  not 
been  produced,  then  there  would  have  been  no  life  on 
the  earth.' l 

Thus,  because  albumen  commenced  to  decay,  the 
principle  of  omne  vivum.  e  vivo  had  to  arise,  since,  had 
it  not  arisen,  there  would  have  been  no  life.  Is  that  a 
scientific  explanation  of  spontaneous  generation  ? 

Such  attempts  render  J.  Reinke's  words  comprehen- 
sible which  he  wrote  of  Naegeli :  c  Thereby  I  think  I 
have  shown  .  .  .  that  the  grounds  put  forward  by  him 
for  the  occurrence  of  spontaneous  generation  can  hold 
water  so  little  that  they  make  the  spontaneous  origin 
of  organisms  appear  as  absolutely  unthinkable/ 3 

We  cannot,  therefore,  see  how  0.  Hertwig  3  can  term 


1  Biol  Zentralbl,  1910,  p.  362,         2  Reinke  :  Die  Weltals  Tat,  p.  337. 
»  Allgemeine  Biologie,  p.  270. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      105 

the  acceptance  of  spontaneous  generation — for  which 
he  himself  can  find  no  grounds  at  all — a  philosophical 
need. 

With  the  reason  for  this  Hackel  should  provide  him  ; 
he  says :  '  We  must  regard  this  hypothesis  as  the 
immediate  consequence  and  the  necessary  completion 
of  the  generally  accepted  theory  of  the  earth's  forma- 
tion of  Kant  and  Laplace ;  and  we  find  therein,  in 
the  totality  of  natural  phenomena,  such  a  compelling 
logical  necessity  that  we  must  therefore  regard  this 
deduction,  which  to  many  appears  a  very  bold  one,  as 
incontrovertible. ' 

The  theory  of  the  earth's  formation,  of  Kant  and 
Laplace,  has  as  '  immediate  consequence '  that  the 
life  on  the  earth  once  began  and  was  not  always  there, 
and  that  is  all ;  regarding  spontaneous  generation 
the  theory  states  nothing. 

Regarding  the  '  totality  of  the  natural  phenomena  ' 
which  here  comes  into  question,  we  can  quote,  also 
according  to  Hertwig's  own  investigations,  the  following 
sentence  :  '  In  the  "  totality  of  the  natural  phenomena  " 
which  here  actually  come  into  consideration,  we  find 
such  a  compulsive  logical  necessity  that  we  must  regard 
the  denial  of  spontaneous  generation  as  incontro- 
vertible/ 

To  these  '  natural  phenomena  '  belongs  in  the  first 
place  the  experimentally  determined  fact,  accepted 
by  all  biologists  ('  axiom '  as  it  is  often  called),  that 
life  now  only  arises  from  the  living. 

To  this  belongs  the    '  impossibility '   of   regarding 


106  THE  THEORY  OF  EVOLUTION 

vital  activity  as  a  chemico-physical  process  even  of 
the  most  complicated  kind,  or  of  regarding  the  organism 
as  merely  a  machine  composed  of  material  parts  held 
together  by  material  forces.1 

It  is  important  to  note  also  the  '  phenomenon  '  that 
all  attempts  have  entirely  failed  to  render  spontaneous 
generation  more  comprehensible  by  means  of  the 
natural  forces  known  to  us,  even  with  the  aid  of  quite 
'  peculiar  '  conditions.  Lord  Kelvin  speaks  of  physical 
'  hocus-pocus/  Helmholz  and  Arrhenius  seize  upon 
the  boldest  hypotheses  in  order  to  avoid  '  spontaneous 
generation/  Reinke  and  E.  v.  Hartmann  find  that 
precisely  these  '  attempts  '  show  the  inconceivability 
of  it.  0.  Hertwig  confesses  that,  '  owing  to  the  present 
position  of  natural  science,  the  investigator  has  cer- 
tainly no  better  prospect  of  results  in  obtaining  living 
from  non-living  material  than  Wagner,  in  Goethe's 
"  Faust,"  of  brewing  a  "  homunculus  "  out  of  a  retort/ 
This  firm  conviction  is  therefore  certainly  based  upon 
the  totality  of  the  natural  phenomena. 

Nor  do  we  avoid  the  c  miracle '  (and  certainly  this 
time  a  true  one)  by  accepting  '  spontaneous  generation/ 
Every  living  organism  shows  to-day  the  persistent 
striving  to  combat,  by  constant  contrivance  (Mauserung), 
the  ageing  and  hardening  tendency  of  its  material  basis,2 
by  fresh  formation  of  highly  complex  and  unstable 

1  Allgemeine  Biologie,  p.  159.     '  Therefore  [by  reason  of  the  "  essential " 
differences  between  mechanical  action  and  vital  activity],  it  is  an  entirely 
vain  endeavour  to  imagine  that  an  organism  can  be  understood  on  the 
principles  of  mechanics.' — Hertwig. 

2  E.  v.  Hartmann  :  Das  Problem  des  Lebens,  p.  204, 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      107 

(labile)  chemical  combinations.  If,  therefore,  the 
organisms  arose  from  inorganic  matter,  then  they  must 
be  struggling  constantly  with  ever-increasing  energy 
against  their  own  nature,  which  compels  them  to  form 
the  most  stable  connections  possible.  f  Every  smallest 
increase  in  the  complication  of  the  chemical  combination 
and  in  the  instability  (labilitdt)  is  contrary  to  natural 
laws,  in  so  far  as  mechanical  conditions  are  not  accepted, 
as  they  cannot  arise  by  themselves  in  conformity  with 
inorganic  laws/ l  If,  despite  this,  '  spontaneous  genera- 
tion '  has  occurred,  then  there  has  happened  a  '  miracle  ' 
in  the  sense  of  modern  natural  science — i.e.  a  breach 
of  Nature's  laws.3 

(c)  Into  the  attempts  to  explain  the  origin  of  life 
by  comparison  with  liquid  crystals  and  by  all  sorts  of 
experiments  with  gelatine  and  artificial  trees,  we  shall 
not  enter.  If  a  liquid  crystal  actually  lives,  why  is 
it  not  left  to  its  fate,  so  that  it  may,  like  bacteria, 
go  further  and  reproduce  itself  ?  That  two  '  liquid  ' 
crystals  run  together  is  very  natural ;  but  it  is  naive 
to  speak  of  copulation  in  the  sense  of  a  melting  of  cells. 
If,  perhaps,  reduction  division  occurs,  have  the  crystals, 
by  complicated  and  wonderfully  purposeful  processes, 
become  desirous  of  and  capable  of  fertilization  ? 

The  '  artificial  plants  '  constitute  certainly  a  very 
amusing  and  interesting  experiment,  similar  to  the 
well-known  'Pharaoh's  serpent'  in  chemistry;  but  if 

1  E.  v.  Hartmann  :  Das  Problem  des  Lebens,  p.  192. 

2  Reinke  says  somewhere  that  if  a  spontaneous  generation  be  accepted 
it  might  also  be  maintained  that  water  formerly  flowed  uphill  and  not 
down. 


108  THE  THEORY  OF  EVOLUTION 

it  is  desired  to  originate  life  thereby,  the  words  of  Lord 
Kelvin,  the  great  physicist,  apply:  'No  hocus-pocus 
of  electricity  or  physics  could  make  a  human  cell/1 

Rhumbler  also — certainly  a  reliable  and  creditable 
investigator — says  of  the  pseudo  organisms :  '  The  whole 
of  the  pseudo  organisms  resemble  the  true  ones,  even 
under  the  most  favourable  conditions,  only  in  the  sense 
of  similar  or  like  configuration  and  in  similar  or  like 
distribution  of  the  aggregate  parts.  Thereby  the 
inorganic  substance  does  not  approach  the  peculiar 
existence  of  the  organic  by  a  hair's  breadth,  any  more 
than  does  any  other  physiological  model  its  living 
original — or  let  us  say,  for  better  exemplification,  than 
a  model  of  a  heart  consisting  of  a  rubber  bag  and  the 
necessary  pumping  apparatus  would  approach  a  living 
heart  whose  beating  only  is  represented  by  the  model/ 3 

§  2.    We  are  not  justified  in  bringing  animals  and  plants 
into  genetic  connection. 

By  animals  we  understand,  as  a  preliminary, 
organisms  like  Mammalia,  Birds,  Fishes,  Worms;  by 
plants,  Trees,  Ferns,  Mosses.  All  that  falls  under  the 
general  category  of '  life/  as  we  have  already  stated,  em- 
braces these  beings.  But  a  dog  behaves  in  many  vital 
ways  differently  from  a  fruit  tree — for  instance,  in  the 
activity  which  he  exhibits  in  seeking  food  or  the  other  sex. 
In  it  we  observe  vital  expressions,  which  are  similarly 

1  See  the  excellent  monograph,   An   ties   Lebens  Schwelle,   Prof.   E. 
Klein,  Luxemburg,  1909,  p.  19. 

2  Ibid.  p.  16. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      109 

executed  as  are,  by  man,  those  actions  which  are  con- 
sciously done,  and  which  he  wills  to  do  in  order  to  attain 
a  certain  object  which  he  recognizes  as,  and  feels  to  be, 
desirable.  The  necessary  movements  in  such  a  case- 
movements  of  the  whole  body  from  place  to  place, 
or  movements  of  certain  parts  (the  hand  for  instance) — 
are  then  so  regulated  as  the  external  impulses  in  the 
particular  case  require.  The  behaviour  of  a  hungry 
dog  who  rushes  towards  a  piece  of  meat  may  serve  as 
an  example.  The  meat  is  obviously  his  recognized 
object,  since  thereto  he  directs  his  staring  eyes,  as 
we  men  are  accustomed  to  do  when  we  have  observed 
something.  Thither  he  wishes  to  go,  since  he  resists 
if  he  is  restrained ;  he  drags  at  the  chain,  always  in  the 
direction  towards  the  meat,  if  he  be  withheld ;  he  feels 
strongly  this  striving  within  himself,  since  he  howls 
and  whines  if  he  be  hindered  in  reaching  the  desired 
object.  In  short,  he  behaves  like  a  man,  who  in  an 
analogous  case  allows  himself  to  be  guided  only  by 
his  sensual  appreciation  and  impulses.  Since,  therefore, 
the  dog  shows  all  expressions  of  a  conscious  sensual 
action,  we  must  concede  to  him  also  the  pre-supposition 
implying  sensual  appreciation  and  impulse ;  otherwise 
we  have  an  insoluble  enigma  before  us. 

This  is  so  because  unconscious  purposeful  move- 
ments either  do  not  come,  in  such  cases,  at  all  into  con- 
sideration— as  for  instance  the  automatic  ones — or  they 
are  not  sufficient — as  with  the  reflex  ones.  '  The  reflex 
respond  to  each  impulse  with  machine-like  regularity, 
always  in  the  same  way,  without  the  slightest  deviation  : 


110  THE  THEORY  OF  EVOLUTION 

their  action  is  monotonous.' l  The  dog,  however,  who 
strives  after  his  food  takes  account  of  the  hindrances 
as  they  present  themselves — he  acts  individually  to 
a  definite  end  ;  for  that  there  suffices  no  organism  of 
machine-like  arrangements,  and  therefore  there  is  no 
reflex  activity. 

All  organisms,  however,  do  not  behave  like  the  dog  ; 
there  are  many  to  which  none  of  the  three  criteria  apply 
which  are  used  in  comparative  physiology  in  the  search 
for  conscious  ('  psychic  ')  vital  expressions,  and  which 
require  the  acceptance  of  true  recognition  and  voluntary 
power  of  striving.  There  are  lacking,  namely,  in  the 
first  place  the  easily  observable  external  signs  of  spon- 
taneous (voluntary)  movements  seen  in  the  larger 
organisms  ;  a  use  or  a  necessity  for  the  vital  impulse 
appears,  furthermore,  to  be  excluded,  since  reflex  and 
other  arrangements  in  the  construction  secure  the 
undisturbed  performance  of  all  the  vital  functions ; 
finally  the  '  organs/  which  may  resemble  animal  ones, 
show  themselves  in  the  clearest  way  to  be  arrangements 
for  the  reception  of  definite  external  e  impulses/  The 
first  two  criteria — the  lack  of  voluntary  motion  and 
the  absence  of  any  necessity  for  the  vital  impulse- 
can  be  deduced  directly  from  the  absence  of  sense 
faculties  in  '  plants  ' ;  the  third— the  possession  of 
special '  organs  ' — proves  nothing,  if  it  be  not  previously 
declared  what  has  to  be  proved.  Since,  however, 
there  are  frequent  references  to  the  new  investigations, 

1  F.  Lucas:  Psychologic  der  niedersten  Tiere,  Vienna  and  Leipzig,  1905, 
p.  11. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      111 

particularly  by  Haberlandt,  into  the  '  sense  organs  of 
plants/  we  will  go  more  closely  into  the  matter. 

What,  in  the  opinion  of  modern  biologists — 
and  particularly  also  of  Haberlandt — is  '  excitability ' 
(ReizbarJceit)  and  what  does  its  presence  imply  for  the 
organism  which  possesses  it  ? 

What  signifies  the  construction  of  particular '  organs  ' 
for  the  reception  of  special  stimuli,  such  as  that  of  light, 
mechanical  pressure,  breakage,  gravity,  etc.,  for  the 
possession  of  actual  sense  faculties — recognition  and 
voluntary  power  of  effort  ? 

From  what  has  already  been  said  regarding  the 
relation  of  the  organisms  to  inorganic  matter  and 
the  general  forces  of  nature,  such  as  light,  warmth, 
gravity,  there  is  a  double  deduction. 

Firstly,  the  organism  needs,  if  it  will  be  active, 
an  influx  of  energy  from  outside  ;  secondly,  it  uses 
this  energy  for  its  own  purposes,  such  as  building 
material  for  instance,  the  formation  of  digestive 
(assimilating)  tissues,  of  conducting  systems  for  the 
nutritive  matter  through  the  whole  body,  of  germ 
cells  from  which  new  individuals  of  its  kind  result,  etc. 

Oxygen,  hydrogen,  carbonic  acid,  sulphur,  phos- 
phorus, lime,  and  the  other  elements  which  exist  in 
the  organism,  also  light,  energy,  electricity,  gravity, 
have  quite  obviously  in  themselves  no  tendency  to 
build  tubes  for  water  conduction  or  blood  circulation, 
or  a  leaf  which  breathes  and  assimilates,  or  an  egg  and 
seed-cell  of  a  fir  tree.  If,  despite  this,  the  chemical 
material  is  necessary  so  that  the  activity  of  the  organism 


112  THE  THEORY  OF  EVOLUTION 

may  be  excited  and  rendered  possible,  then  can  they 
only  be  regarded  as  '  impulsions/  as  building  material 
and  sources  of  energy  ;  they  form,  as  is  very  significantly 
expressed,  '  stimuli ' — i.e.  impulses  and  material  for 
carrying  on  the  life  of  the  organism.  The  capacity  of 
the  living  body  to  respond  to  an  external  impulse 
with  vital  expressions,  such  as  growth,  formation  of 
fruit,  or  attractive  or  repulsive  movements,  is  called 
'  excitability  '  (Reizbarkeit) . 

1  Excitability/  taken  in  this  sense,  signifies  thus 
as  much  as  vital  capability  in  general  and  is  the  peculiar 
mode  of  reaction  of  all  organisms  in  response  to  external 
influences  in  contrast  to  the  behaviour  of  inorganic 
bodies  under  like  influences.  We  are  not  alone  in 
this  conception  :  it  is  put  forward  and  established  by 
very  eminent  biologists,  such  as  Pfeffer,  Strasburger, 
0.  Hertwig,  Sachs,  and  others. 

In  the  '  Lehrbuch  der  Botanik '  of  Strasburger, 
Noll,  Schenk,  and  Schimper !  so  extensively  used  in 
the  German  high  schools,  there  is  the  following  defi- 
nition of  '  excitability ' :  '  It  is  shown  thereby  that  ex- 
ternal or  internal  impulses  given  to  the  living  organism 
act  as  dissociating  stimuli  and  induce  activities 
which  it  effects  with  means  over  which  it  has  control 
or  which  it  is  capable  of  obtaining,  and  in  a  manner 
determined  by  its  construction  and  by  its  needs.  Even 
in  the  smallest  and  simplest  organism  of  which  we 
know,  the  vital  processes  depend  on  such  stimuli/ 

1  Lehrbuch  der  Botanik  fur  Hochschulen,  Jena,  1900,  p.  4. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      113 

According  to  Pfeffer l  the  stimuli  are  associated 
with  the  whole  of  the  vital  action,  and  there  is  perhaps 
no  single  action  '  in  which  these  do  not  and  must  not 
play  a  role  .  .  .  they  are  thus  a  general  quality  of 
all  living  substance/ 

Haberlandt  calls  '  all  organisms,  animals  and  plants, 
excitable/  3  Then  follows  almost  word  for  word  the 
definition  given  above  by  Strasburger.  Similar  opinions 
were  already  held  by  Treviranus ;  Haberlandt  says 
of  him,3  '  that  he  had  correctly  grasped  the  signification 
of  vital  excitation/  Treviranus,  however,  attributes 
the  whole  vital  process  to  stimuli. 

The  term  '  excitability '  may,  however,  be  more 
narrowly  defined,  as  is  done  by  Haberlandt  in  his 
work  '  Sinnesorgane  im  Pflanzenreich/  He  discusses 
therein  the  special  arrangements  of  many  plants  where- 
by '  the  sudden  deformation  of  the  sensitive  proto- 
plasm which  is  essential  to  the  "  excitation  "  becomes 
particularly  easy  and  marked.  This  is  also  the  most 
general  building  principle  of  this  apparatus/  4< 

Many  plants  have  thus --and  this  Haberlandt  has 
described  in  a  masterly  fashion  and  determined  by 
experiment — special  apparatus  for  receiving  definite 
stimuli  —  for  instance,  mechanical  contacts.  Such 

1  In    Pflanzenphysiologie,    I,    Leipzig,    1897,    p.  10,    Pfeffer   objects 
*  emphatically  '  to  the  assumption  that  only  certain  striking  phenomena 
of  motion  were  due  to  excitation,  as,  for  instance,  the  sudden  movement  of 
the  sensitive  plant  Mimosa  pudica  (p.  11). 

2  G.  Haberlandt:  Physiologische  Pflanzenanatomie,Lei$zig,  1909,  p.  520. 

3  Sinnesorgane  im   Pflanzenreich  zur  perzeption  mechanischer  Reize, 
Leipzig,  1906,  p.  4. 

4  Parenthesized  in  the  original. 


114  THE  THEORY  OF  EVOLUTION 

apparatus  are  particularly  favourably  placed  in  the 
organism,  and  their  entire  anatomical  structure  shows 
clearly  that  their  object  is  that  the  external  influences 
shall  act  vigorously  and  directly  upon  the  right  spot. 
Does  this  afford  any  proof  that  the  actions,  which 
are  produced  by  such  'organs/  are  accompanied  by 
consciousness  ? 

Quite  certainly  this  is  not  the  case.  According  to 
Haberlandt  himself  a  similar  capacity  for  perception 
of  mechanical  excitation  exists  in  other  plants,  but 
'  diffused ' — for  instance  in  all  the  cells  of  a  leaf  or 
leaf  tissue  or  stalk.1  The  development  of  particularly 
localized  apparatus  with  the  exclusive  function  of 
responding  to  excitation  increases,  it  is  true,  the  general 
'  faculty  of  perception  '  and  can  be  adapted  to  special 
purposes — as,  for  instance,  sudden  and  powerful  move- 
ments, but  it  alters  the  nature  of  the  excitability 
absolutely  not  at  all. 

So  long,  therefore,  as  it  is  not  shown  that  'excit- 
ability '  implies  quite  general  '  psychical '  qualities, 
there  is,  by  those  organs,  nothing  gained  at  all  for 
the  acceptance  of  conscious  vital  phenomena  in  plants. 
A  careful  study  of  the  illustrations  enables  us  also  to 
recognize  without  difficulty  the  typical  form  of  reflex 
mechanism,  not  only  in  the  organs  for  mechanical 
stimuli  but  also  those  of  gravity  and  light. 

Furthermore  Haberlandt  quite  emphatically  remarks 
that  for  him  the  '  psychical '  side  of  the  sensitiveness 
'  is  an  accompanying  or  parallel  phenomenon  outside 

1  Physioloyische  Pflanzenanaiomie,  p.  520. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      115 

the  scope  of  his  investigations/  [?]  For  us  that  is  not 
the  case,  since  here  it  is  not  a  question  whether  the 
plants  really  have  organs  for  the  reception  of  stimuli, 
but  whether  they  have  sense  organs.  We  can  and  must 
separate  these  questions,  since  with  us  men  there 
occur  purposeful  excitations  which  happen  uncon- 
sciously (for  instance  reflex  action),  and  such  as  we 
voluntarily  produce,  with  consciousness  due  to  an 
internal  or  external  stimulus.1  Among  the  animals  also 
we  have  both  kinds  of  movements ;  to  the  plants  there- 
fore we  must  apply  the  psychological  criteria  in  order  to 
settle  the  question.  That,  however,  was  not  the  case 
with  Haberlandt ;  his  text  and  his  illustrations  permit, 
moreover,  of  only  the  one  deduction — that  we  have  to 
deal  with  indubitable  mechanisms,  with  reflex  actions. 

Conclusion. — There  are,  therefore,  organisms  which 
show  clear  expressions  of  conscious  vital  action,  of 
sensible  recognition  (sensations  and  feelings),  and  striving 
power,  and  others  in  which  such  expressions  are  never 
observed,  not  even  in  the  most  imperfect  state.  The 
first  we  call  '  animals/  the  second  '  plants/  Conscious- 
ness we  cannot,  however,  regard  as  something  of  secon- 
dary importance,  since  '  the  entry  of  the  conscience 
into  the  series  of  vital  phenomena  must  not  appear 
to  us  as  an  incomprehensible  miracle  but  as  something 
natural  and  easily  comprehensible,  and  that  is  the  case 
if  consciousness,  from  the  very  commencement,  already 
at  its  first  appearance  has  a  definite  task  to  fulfil  in 
the  service  of  the  whole  organism  like  every  other 

1  See  Wasmann  :  Instinkt  und  Intelligenz  im  Tierreich,  1905,  p.  6. 

12 


116  THE  THEORY  OF  EVOLUTION 

vital  phenomenon/  l  The  entire  vital  activity  depends, 
then,  in  animals  upon  their  sense  faculties,2  since 
reflex  action  alone  would  not  suffice  either  for  obtaining 
food,  or  for  protection  against  attack,  or  for  reproduc- 
tion. In  plants,  on  the  contrary,  it  is  positively  provided 
for  that  they  have  always  their  nutrition  surrounding 
them  —  air,  water  and  salts  in  solution  —  and  that  the 
pollen  reaches  the  female  flower  by  self-pollination  or 
with  the  aid  of  the  wind  or  even  of  insects  specially 
fitted  for  the  office.  Consciousness  is  here  positively 
superfluous. 

We  came  earlier  to  the  conclusion  that  in  each 
organism  a  single  principle  is  to  be  accepted  which 
stands  above  matter  and  utilizes  its  materials  and 
energies  unitedly,  since  inorganic  material  never  shows 
the  trace  of  a  tendency  to  collect  into  mutually  co- 
operating systems  with  a  purposeful  division  of  the 
vital  functions.  Now  we  have  learnt  to  know  of 
organisms,  the  animals,  into  which  a  new  factor  in 
vital  activity  is  purposefully  interposed  —  i.e.  sensible 
recognition  and  voluntary  power  of  action.  That  is,  that 
there  is  a  principle,  which  in  the  dog,  for  instance,  leads 
and  directs  the  life,  and  possesses  also  the  sense  faculties, 
since,  exactly  like  the  other  faculties,  they  are  utilized 
to  one  and  the  same  vital  end.  Thus  the  entire  f  psyche  ' 
of  the  animal  is  another  than  that  of  the  plants,  which 
display  no  consciousness.  Should,  therefore,  a  plant 


1  F.  Lucas:  Psychologic  der  niedersten  Tiere,  Vienna  and  Leipzig,  1905, 
p.  18. 

2  See  Wasmann  :    Die  psychischen  Fahigkeiten  der  Ameisen,  1909,  p.  5. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      117 

become  an  animal,  the  whole  nature  of  its  principle 
must  be  transformed,  and  only  when  this  transforma- 
tion is  complete  can  consciousness  show  itself  for  the 
first  time.  A  thing  '  a/  however,  which  can  only  become 
a  thing  c  b '  by  a  total  alteration  of  its  whole  being,  abso- 
lutely excludes  all  connection  with  '  b  '  by  gradual  evolu- 
tion ;  because  though  evolution  may  effect  development 
of  a  basis  or  the  improvement  of  a  completed  object  if 
the  necessary  evolutional  tendency  leads  thereto,  it 
cannot  effect  new  and  higher  modes  of  existence. 
Animals  and  plants  cannot  therefore  be  brought  into 
genetic  connection ;  the  question  of  the  origin  of  the 
animals  from  plants  forms  no  problem  of  tbe  hypothesis 
of  evolution. 


§  3.  We  are  not  justified,  in  the  present  state  of  our 
knowledge,  in  bringing  the  families  and  classes  of  the 
animal  and  plant  worlds  into  genetic  connection. 

(1)  Introductory  remarks,  on  the  systematic  treatment 
of  animals  and  plants. 

The  systematic  division  of  the  animal  kingdom 
has,  since  Cuvier,  been  effected  mainly  according  to 
two  points  of  view1 — according  to  their  affinity  to  a 
definite  type  (form  of  construction),  and  according  to 
the  height  of  their  organization.  The  type  arises 
from  the  mutual  relative  positions  of  the  organs  in  the 
organism  and  the  symmetry  of  the  whole  ;  the  height 

1  See,  e.g.,  B.  R.  Hertwig :  Lehrbuch  der  Zoologie,  Jena,  1910,  p.  104. 


118  THE  THEORY  OF  EVOLUTION 

of  the  organization  from  the  degree  of  perfection — i.e. 
from  the  greater  or  less  strictly  executed  distribution  of 
the  separate  vital  functions  to  special  tissues,  i.e.  organs. 

The  '  type  '  determines  by  itself  alone  nothing  as 
regards  the  perfection  of  the  animal ;  the  degree  of 
differentiation  in  separate  tissues  and  organs  yields,  how- 
ever, an  objective  criterion — i.e.  one  based  on  reality— 
of  the  height  of  organization.  That  applies  particularly 
also  to  the  differentiation  of  the  nervous  system.1 
According  to  the  '  plan  of  construction  '  and  the  height 
of  organization  there  is  effected  also  at  present  the 
systematization  of  the  animals  and  plants  into  a  few 
well-defined  groups. 

As  a  rule  the  zoological  textbooks  divide  the  animal 
kingdom  into  seven,  nine,  and  even  more  families 
(Stamme).  R.  Hertwig  holds  to  seven  in  his  well-known 
'  Lehrbuch  der  Zoologie/  E.  Selenka 3  adopts  ten 
and  distinguishes  them  as  follows  : 

I.  Monocellular  Protozoa  (1) 

II.  Leaf  animals  (Metazoa)  witli  cellular 
differentiated  tissues  and  organs: 

1.  No  bodily  cavity  as  blood  reser- 
voir ;  Coelenterata  : 
(a]  Bodies  non-symmetrical  Spongise  (Sponges)  (2) 

1  Recently  here  and  there  the  biologists  have  been  denied  all  right  to 
speak  of  various  grades  of  perfection  or  heights  of  organization,  or,  at  the 
best,  they  are  yielded  to  only  for  practical  reasons  (by  reason  of  the  division 
of  matter).      See  B.  Franz  in  Biol.  Zentralblatt,  1911,  p.  1 :     '  What  is  a 
higher  organism  ?  '     We  shall  refer  again  to  this  article. 

2  Zoologisches  Taschenbuch,  I,  Lepizig,  1897,  p.  1.  For  quick  information 
the  two  volumes  of  this  handbook  are  much  to  be  recommended  ;   they  will 
always  provide  a  clear  and  short  grounding  in  the  systematic  arrangement. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      119 

(b)  Bodies  four  to  six-rayed ;  possess  ^          Cnidaria  (3) 

stinging  cells  J  (Polyps  and  Medusae). 

2.  Body  cavities  (at  least  as  a  split) ; 

Coelomata  : 

Echinodermata  (4) 


(Sea  Urchins,  Starfish) 


(a)  Body  five-rayed  (symmetrical)  ; 

body  wall  strengthened  with  a 
lime  skeleton 

(b)  Body  laterally  symmetrical,  bi- 

lateral : 

(a)  Central  nervous  system  is  not 
a  dorsal  tube ;  no  internal 
axial  skeleton  : 

A.  Body    without   limbs,    or, 

limbed,  without  divided  ex-  j-  Vermes  (Worms)  (5) 
tremities 

B.  Bodies    without    limbs,    with  \ 

r  Mollusca  (6) 

three    pairs     mam     ganglia  .      ,      «     ., 

\>       x  HSoft  animals,  Snails, 
(nerve   cell    agglomerations)  i  v        0     . , 

-^  t  u  11  Squids,  etc.) 

with  toot,  mantle,  and  shell  } 

C.  Bodies   limbed    with   divided)          Arthropoda  (7) 

extremities  /  (Insects,  Spiders,  Crabs) 

(ft)  Central  nervous  system  in 
spine  ;  bodies  limbed  : 

A.  As  axial  skeleton  only  a  chorda 

dorsalis  (dorsal  chord,  a  soft  \ 
rod);   Chordata  Tunicata  (8) 

Limbs   and  Chorda    confined  (  (Mantelthiere,     Seeschei- 
to    hinder    parts    of    body  j  den). 

Limbs  extend  throughout  the  (         ^eptocardii  (9) 
b  I  (e.g.      Amphioxus,      the 

Lancelet  fish) 

B.  With  the  Chorda  is  associated  )    yertebrata  /10j 

the   spinal  column   and  the     (the  yertebrates) 
skull  / 


120 


THE  THEORY  OF  EVOLUTION 


For  the  tabulation  of  subdivisions  (classes  of  the 
family)  no  generally  available  criteria  can  be  given. 
A  textbook  of  geology  should  be  read  in  that  connec- 
tion ;  as  concerns  systematic  arrangements  Selenka's 
'  Zoologisches  Taschenbuch  '  is  the  best. 

We  will  now  give  an  example  from  the  last-named 
work.1  Many  of  the  characters  described  must  be 
simply  taken  as  '  given/  They  contribute  much  to  the 
total  habit,  but  we  cannot  speak  of  higher  or  lower 
forms. 

Typical  Differences  between  Reptiles  and  Mammalia. 
KEPTILES.  MAMMALIA. 


Skin  scaly,  offering  no  pro- 
tection against  cold ;  temperature 
changeful  (Poikilotherm). 


Skin  protected  from  cold  by 
hairy  coat  or  cushion  of  fat  ; 
temperature  even  and  high. 


Larger  and  smaller  circulation,  Perfectly    separated;     active 

mostly    and    imperfectly    sepa-  assimilation, 
rated ;  slow  assimilation. 

Lungs  sack-like,  of  small  super-  Lungs    alveolar,     with    large 

ficies  reaching  to  the  abdomen  ;  surface  confined  by  diaphragm 

chest  small.  (breathing    muscle)    in   thorax ; 

chest  broad. 

Mainly  dependent   on  animal  Manifold  provision,  hence  dis- 

food    and    warm    climate.     The  tribution   more   extended.     The 

ovum    is    developed    by    aerial  ovum  is   hatched   by   maternal 

temperature.  warmth. 


Teeth  alike  ;  persistent  change 
of  teeth  (polyphyodont).  Vege- 
tarians are  monophyodont  or 
anodont  (Tortoises). 

1  Selenka  :  Zoologisches  Tascheiibuch,  I,  p.  190. 


Teeth  dissimilar  ;  stomach  re- 
lieved by  grinding  of  food  ;  jaw 
typically  diphyodont. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      121 


KEPTILES. 

Front  of  brain  small,  olfactory 
centre  well  developed. 


One  olfactory  muscle. 

Neck  immoveable  ;    one  con- 
dyle  (swelling  behind  head). 

Oviparous  ;    eggs  with  shells 
and  with  abundant  yolk. 


MAMMALIA. 
Front    of    brain    large ; 


all 


Allantois  (an  embryonal  for- 
mation) is  the  urine  bladder 
and  breathing  organ. 


organs  of  sensation 
higher  sensitive  centres  in  the 
brain ;  gradual  progress  in 
intelligence  (?). 

Three  or  more  olfactory  glands. 
Neck  moveable ;  two  condyles. 

Viviparous  ;  eggs  with  little 
yolk  or  none.  Ovum  is  con- 
stantly nourished  by  maternal 
secretions  (uterine  mucus,  uter- 
ine milk,  blood  serum  and,  later, 
milk). 

Allantois  is  only  the  bladder 
(many  marsupials)  or  also  the 
bearer  of  the  embryonal  placental 
vessels. 


Greater   abundance   of   forms         Greater   abundance   of   forms 
in  the   Permian   formation   and     in  the  recent  Tertiary  formation, 
until  those  of  the  Jura  and  the 
Chalk. 

The  orders  in  the  class  of  the  Mammalia  are  deter- 
mined essentially  on  the  basis  of  different  construction 
of  the  extremities  and  of  the  jaw. 

The  plants  are  generally  divided  into  five  series 
or  families.  This  is  done  mainly  according  to  the 
degree  of  differentiation  in  the  first  place  of  the  greater 
groups  of  tissue — the  roots,  stem,  leaf  and  flower — then 
according  to  the  greater  or  less  perfect  distribution 
of  work  in  the  organ  formation  and  the  purposeful 


122 


THE  THEOKY  OF  EVOLUTION 


constitution  of  the  separate  tissues  (conduction,  as- 
similation, protection,  etc.),  and  according  to  the 
reproductive  arrangements. 

Warming  l  establishes  five  series. 
1.  Thallophyta  or  Sessile  Plants. — One  or  more 
celled  plants  of  simple  construction, 
almost  always  without  limbs  in  the 
root,  stem,  and  leaves  (such  an 
undivided  plant  body  is  styled 
Thallus),  and  always  without  vas- 
cular bundles  2 — Algae,  Fungi,  and 
Lichens. 

2.  Bryophyta  or  Mosses. — Small 
plants  with  thallus  or  leaved  stalks, 
but  without  true  roots 3  and  with 
vascular  bundles.  The  group  of 
Mosses  is  sharply  differentiated  from 


FIG.  25.  — A  Moss— 
Hypnum  Purum.  k, 
the  spore  capsule  ,  ,,  ,, 

with  its  stalk,  seated      the  following  groups  by  the  peculi- 

on  the  '  moss  plant- 
let  '    and     produced 


from      a      fertilized 
ovum. 


arity  of  its  reproductive  changes. 
The  green   moss    plant — that  is 

what  the  layman  generally  under- 
stands by  '  moss  ' — produces  in  separate  receptacles 
both  ova  and  motile  antherozoids.  The  ova  receptacles 
are  called  archegonia,  those  of  seed  cells  antheridia. 

1  Handbuch  der  systematischen  Botanik,  German  edition,  Berlin,  1902, 
p.l. 

2  Vascular  bundles  are  essentially  bundles  of  conducting  tubes  for  the 
transport  of  water  and   the  dissolved  earthy  salts   contained   therein   to 
the  leaves  and  other  organs. 

3  '  True  '  roots — i.e.  roots  with  varied  tissues.     The  Mosses  have  only 
'  Rhizoids' — i.e.  threads  formed  of  like  rows  of  cells  or  even  only  of  undivided 
protoplasmic  tubes.     Rhizoids  are  therefore  imperfect — '  pseudo  ' — roots. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      123 

From  the  fertilized  ovum  the  green-leaved  moss  plant 
is  not  immediately  produced,  but  it  forms  in  the  first 
place  another  '  plantlet ' — the  sporogonium  (Fig.  25). 
When  complete  it  consists  of  a  stalk  (seta)  which 
carries  a  capsule  at  its  tip.  The  stalk  is  sunk  within 
the  mother  plant,  without,  however,  an  actual  con- 
nection by  growth  existing.  In  the  capsule  there  are 
finally  numerous  spores  which  are  newly  formed  out  of 
an  '  indifferent '  tissue. 

By  the  bursting  of  the  capsule  the  spores  are  hurled 
out,  and  only  from  these  are  there  again  developed 
the  green  '  moss  plants/ 

In  regular  succession  there  thus  arise  individuals 
which  produce  the  sexual  cells  proper — viz.  ova  which 
need  fertilization,  and  seminal  threads  (antherozoids 
in  the  plants  concerned),  and  form  others,1  the  spores  3 
or  germ  cells,  protected  by  a  firm  skin,  which  never 
require  to  be  fertilized,  at  least  not  with  seminal  threads, 
in  order  to  develop.  This  regular  succession,  one  after 
the  other,  of  a  sexual  and  asexual  generation,  is  termed 
'  alternation  of  generations/ 

1  Is  the  Sporogon  an  actual '  individual ' — i.e.  a  new  actual  plantlet — or 
an  organ  of  the  mother  plant  for  the  formation  of  reproductive  cells  ? 
It  is  very  difficult  to  decide  the  question,  but  for  our  description  it  has 
no  importance,  since  we  here  consider  only  the  actual  differences  which 
can  justify  us  in  determining  separated  types.     For  the  actual  plant  (not 
organ)  nature  there  speak  the  formation  of  various  tissues  with  separate 
vital  functions,  assimilation  tissues,  breathing  apparatus  (stomata),  and 
the  circumstance  that  the  germ  cells  (spores)  are  newly  developed  from 
indifferent  material.     The  spores  are  therefore  not  the  immediate  product 
of  the  self -dividing  fertilized  ovum  cell. 

2  It  would  go  too  far  to  enter  exactly  into  the  definition  of  the  '  spore.' 
The  definition  given  above  in  any  case  suits  the  plant  spores  generally. 


124 


THE  THEORY  OF  EVOLUTION 


3.  Pteridophytes  or  Ferns. — Plants  with  stalk, 
leaves,  and  true  roots ;  vascular  bundles  without  '  true ' 
vessels.1  The  alternation  of  generation  is  quite  differ- 
ent from  that  of  the  Mosses.  The  green  plants  (which 
the  layman  only  knows  as  the  Fern)  carry  spore- 
containing  vessels  (in  which  there  is  no  ovum  as 


A 


B 


FIG.  26. — NEPHRODIUM  filix  mas.  A — Pro- 
thallium  from  the  under-side  with  archegonia  ar ; 
antheridia  an;  root-hairs  rh.  B — Prothallus 
with  young  fern  produced  from  a  fertilized  ovum. 
b,  fern  leaf ;  w,  root  of  same.  Mag.  about  8  diam. 
(After  Strasburger. ) 

with  the  Mosses).  From  the  spores  scattered  on  the 
ground  there  are  developed  so-called  prothalli,  in 
which  true  ova  and  seminal  threads  are  formed.  It  is 
only  the  fertilized  ovum  which  reproduces  the  green 
fern  plant  directly  (Fig.  26). 

'  True  '  vessels  (trachei)  =  conducting  tubes  in  which  the  transverse 
walls  of  the  rows  of  cells  which  form  such  a  tube  become  absorbed.  By 
this  means  the  conduction  of  water  is  certainly  facilitated  and  hastened. 
In  the  '  Tracheids  '  the  transverse  walls  of  the  separate  cells  are  retained. 
That  is  the  main  difference. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      125 

Two  sorts  of  spores  occur — microspores  which  form 
prothalli  with  seed-vessels,  antheridia,  and  macrospores 
which  produce  such  with  embryo  ova  (archegonia). 

Four  classes  of  this  series  are  determined  :  Ferns 
(Filicinae),  Equisetums  (Equisetae),  Lycopods  (Club- 
mosses),  Water  Ferns  (Hydropteridse). 

4.  Gymnospermae  or  Naked-seeded  Plants. — Woody 
plants  with  separated  male  and  female  flowers.     In 
the  stamens  are  produced  multicellular  pollen   grains 
which  are  carried  by  the  wind  direct  to  the  more  or 
less    obvious    (naked-seeded)    female    embryo    seeds. 
Several  embryo  ova  are  found  in  the  embryo  seed. 

The  first  classes  of  this  series  are :  Cycadinao 
(Sago  or  Fern  Palms),  Ginkgoinae  (a  still  living  species 
is  GinJcgo  biloba),  Coniferae  (Fir  Trees),  Gnetinae  (a 
small  exotic  group). 

5.  Angiospermse   or   plants   with   covered  seeds.— 
The  flowers  often  contain  both  male  and  female  organs 
at  the  same  time  ;    more  rarely  these  are  borne  in 
separate  flowers  or  even  separate  plants.     The  pollen 
grains  are  only  two-celled  ;   fertilization  can  only  occur 
when  the  pollen  grains,  on  germination  on  the  stigmatic 
surface,  send  a  tube  down  through  the  entire  stalk  till 
it  reaches  the  entirely  enclosed  embryo  ova  in  the  seed 
vessel.     Each  embryo  only  contains  one  ovum. 

The  chief  divisions  are  :  Monocotyles  and  Dicotyles. 
The  series  4  and  5  are  distinguished  from  the  other 
three  as  flowering  or  seed-bearing  plants.  A  flower 
is  produced  at  the  terminal  point  of  a  shoot  and  con- 
sists exclusively  of  reproductive  organs.  The  leaf 


126 


THE  THEORY  OF  EVOLUTION 


FIG.  27. — a,  Ripe  pollen  grain  of 
an  Angiosperm  ;  b, '  germinat- 
ing '  pollen  grain ;  g,  generating 
germ ;  v,  vegetative  germ. 


formation  is  transformed  either  into  fruit  or  pollen- 
bearing  leaves,  or  into  protective  or  attractive  means  in 

connection  with  the  fertiliza- 
tion. '  Seed  plants  '  they  are 
called  because  it  is  through 
the  seed  that  the  formation  of 
new  individuals,  separated 
from  the  mother  plants,  is 
effected.  A  seed  is  a  multi- 
cellular  body,  which,  when  it 
leaves  the  mother  plant,  is  already  differentiated  (a 
grain  of  wheat,  an  apple  pip). 

It  has  been  possible  to  establish 
the  existence  of  an  alternation  of 
generations  in  the  Gymnosperms 
and  Angiosperms,  but  certainly  of  a 
very  debased  kind.  A  series  of  in- 
dications point  to  the  pollen  grains, 
and  the  so-called  embryo  sac  in  the 
bud  germ,  as  being  '  spores/  since 
they,  in  the  first  place,  without  fer- 
tilization, form  a  sort  of  prothallus 
(second  individual  ?)  in  which  first 
arises  the  fertilizing  cell  proper 
(sexual  cell  or,  better,  sexual  germ). 
The  prothallus  possesses,  it  is  true, 
in  some  Gymnosperms  only  three 
small  cells,  or  even  only  one  in  the  Angiosperms — the  so- 
called  vegetative  cell  (Fig.  27).  The  macrospores  produce, 
on  the  other  hand,  in  the  Gymnosperms  a  particular 


FIG.  28. —SECTION 
THROUGH  THE  EM- 
BRYO SEED  OF  A 
GYMNOSPERM  (Picea 
vulgar  is], 

E,  ovum ;  e,  embryo 
sac  (Endosperm)  = 
prothallus ;  p,  two 
pollen  grains  which 
send  tubes  down  to 
the  embryo  ova. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      127 


tissue  in  addition  (endosperm)  in  which  several  ovum 
cells  can  be  deposited  (Fig.  28).  In  the  Angiosperms 
there  still  remain  three  cells,  which  may  be  regarded 
as  a  prothallus  (the  so-called  three  antipodes).  There 
is  never  more  than  one  ovum  formed  (Fig.  29). 

The  determination  of  classes 
within  these  series  is  effected 
mostly  according  to  the  construc- 
tion and  the  position  of  the  spores 
—or  the  ovum  and  seed  vessels, 
the  formation  and  arrangement  of 
the  leaves,  the  small  or  tree-like 
constitution  of  the  stem  (stalk), 
etc.  From  all  this  there  results  a 
habit  of  growth  which  is  fairly 
characteristic  but  can  only  be  suf- 
ficiently known  by  seeing  the 
plants. 

As  an  example  we  will  describe 
the  classes  of  the  Pteridophytes 
(after  Warming). 

Class  1 :  True  Ferns  (Filicinse) 
and  Hydropteridse  (Water  Ferns). 

(a)  Habit  mostly  herbaceous ; 

leaves  alternate,  large  in  comparison  with  the  stem  and 
highly  developed  (feathery)  ;  when  young,  circinately 
rolled  (mostly). 

(b)  Peculiarities  of    the  reproductive  organs  :    the 
spore-cases  are  situated  on  the  edge  or  on  the  back  of 
ordinary  leaves ;    only  in  some  cases   are  the  fruitful 


FIG.  29.—  Et  Fruit  bud 
of  an  Angiosperm  (Poly- 
gonum  convolvulus)  dur- 
ing fertilization.  Pol- 
len grains  and  pollen 
tubes  as  above,  e,  em- 
bryo sac  ;  E,  the  one 
ovum  cell  (the  two 
others  do  not  become 
fertilized).  A,  the  three 
antipodes  (=pro- 
thallus). 

(After  Strasburger.) 


128 


THE  THEORY  OF  EVOLUTION 


(spore-bearing)  leaves  specially  changed.  The  fertile 
leaves  are  not  confined  to  definite  parts  of  the  caudex 
and  do  not  limit  its  growth. 

The  '  Water  Ferns '  are  small  plants  with  a  hori- 
zontally growing  stem  which  creeps  on  the  ground  or 
floats  on  the  water.  They  are  heterosporous — i.e.  they 

produce  in  separate  vessels 
micro-  and  macrospores  ;  the 
true  Ferns  are  homosporous, 
with  only  one  kind  of  spore. 

Class  2:  Equisetinse 
(Horsetails). 

(a)  Herbaceous    (all    the 
present   forms)  ;    the    leaves 
relatively    small,    undivided, 
arranged     in     whorls,     and 
branched  (Fig.  30). 

(b)  The  spore  capsules  are 
situated  on  peculiarly  meta- 
morphosed leaves  which  are 

conjoined  into  a  single  bloom  (so  called)  which  terminates 
the  growth  of  the  shoot.  The  branches  are  arranged 
in  whorls — i.e.  they  spring  at  even  distances  and  all  in 
the  same  plane  on  the  stem. 

Class  3  :   Lycopodinae  (Club -mosses). 

(a)  Herbaceous  (all  the  present   ones) ;  the  leaves 
very  small  and  simply  constructed  (almost  scale-like). 

(b)  The  sporangia  (spore  vessels)  are  situated  singly 
on  the  base  of  the  upper  side  of  the  leaf,  or  in  the  leaf 
axis,  or  above  the  axis  on  the  stem  itself. 


FIG.  30  . — HABIT  OF  AN  EQUISE- 
TUM  (Equisetum  arvensc).  a, 
barren  shoot ;  b,  fertile  shoot ; 
c,  portion  of  stem. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      129 

The  '  fertile '  leaves,  which  are  united  in  special 
clusters  at  the  tips  of  the  shoots  (stalks)  and  hence 
terminate  the  growth  (Fig.  31),  are  very  often  differently 
formed  to  the  barren  ones. 


(2)  General  results  of  systematic   classification  com- 
pared with  those  of  palceontology. 

From  the  above  it  is  clear 
that  a  priori  we  cannot  know 
whether  our  systematic  cate- 
gories are  really  primary  and 
do  not  signify  forms  of  animals 
and  plants  which  are  reducible 
one  from  another,  i.e.  true 
types  in  the  sense  of  Cuvier. 
Both  elements  which  present 
themselves  in  the  definition  of 
a  '  type  ' — plan  of  construction 
(symmetry,  habit  as  a  whole), 
and  the  degree  of  differentiation 
in  tissues  and  organs  for  the 
general  vital  activities — can  in 
themselves  be  subject  to  variation.  It  may  therefore 
happen  that  family  and  class  characters  may  have  arisen 
out  of  other  forms. 

It  is  therefore  from  the  outset  not  excluded  that, 
for  instance,  all  plants  which  have  been  assembled 
under  the  classification  of  Ferns  are  only  various  modifi- 
cations of  one  and  the  same  form  of  growth  and  have 


FIG.  31. — HABIT  OF   A    CLTJB- 

MOSS  (Lycopodium  clavatum). 
a,  so-called  'bloom'  =  clus- 
ter of  spore  vessels  ;  k,  sepa- 
rate sporangium  burst  open ; 
s,  leaflet  (scale). 


130  THE  THUOBY  OF  EVOLUTION 

arisen  through  the  development  and  evolution  of  one 
original  form. 

The  possibility  that  Ferns,  Equisetse,  and  Club- 
mosses  might  be  traced  back  to  a  common  starting- 
point  cannot  be  a  priori  disproved. 

But  one  circumstance  must  be  expressly  emphasized. 
The  differences  which  exist  between  the  classes  and  the 
families  of  animals  and  plants  are  the  first  in  the  organic 
kingdom  which  may  be  bridged  over  by  evolution : 
the  question  whether  and  how  the  associated  forms 
now  in  existence  can  be  regarded  as  the  results  of 
developmental  (evolutionary)  process  is  the  first 
problem  of  an  evolutional  hypothesis.  The  evolution 
must  not  here,  in  this  question,  be  regarded  as  in  any 
way  put  forward  as  a  fact :  that  would  be  quite 
inadmissible. 

No  one  has  so  far  maintained  that,  on  closer  study 
of  the  relations  between  the  inorganic  and  organisms, 
or  between  animals  and  plants,  positive  starting-points 
for  the  acceptance  of  an  evolution  have  been  found. 
Spontaneous  generation  is  put  forward  by  investigators 
exclusively  as  a  postulate,  as  we  have  seen  ;  the  trans- 
formation of  a  plant  into  an  animal  is  little  discussed, 
and  it  is  simply  impossible  to  explain  it  by  '  evolution/ 

Consequently  the  testing  of  the  connection  of  the 
greater  systematic  groups  among  themselves  is  of 
fundamental  importance  for  the  evolution  question, 
since  here  for  the  first  time  a  genetic  connection  is 
not  from  the  outset  excluded. 

From  the  results   of  the   systematic   classification 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS    131 

of  the  present  organisms,  compared  with  those  of 
palaeontology  which  we  have  discussed  above,  there 
are  deduced,  as  it  appears  necessarily,  the  following 
conclusions : 

1.  The  generally  accepted  and  usually  corresponding 
separation  of  all  the  recent  organisms  into  a  number 
of  groups  shows  that  there  are  really  certain  gradings 
existent.    We  are  in  the  great  majority  of  cases  not 
long  in  doubt  whether  a  plant,  for  instance,  belongs  to 
the  Ferns  or  Equisetums  or  Angiosperms. 

If  difficulties  arise,  they  do  so  almost  always  on 
account  of  peculiarities,  which  we  may  justifiably 
consider  as  due  to  secondary  '  adaptive  phenomena ' 
(specialization  or  regression).  The  study  of  the  repro- 
ductive relations,  with  which  in  most  cases  are  asso- 
ciated other  characteristic  features,  finally  determines 
the  systematic  position. 

2.  All  certain  results  of  palaeontology  indicate  that 
the  still  surviving  higher   systematic    categories  were 
retained   also   during  the   geological  periods,   so   that 
we  can  class  the  greater  part  of  the  fossil  forms  with 
the  recent  ones  in  the  same  system.1 

Of  clear  transitions  between  Pteridophytes,  for 
instance,  and  Gymnosperms  nothing  can  be  said  ;  what 

1  To  class  together  fossil  and  recent  forms  as  equivalent  and  closely 
associated  orders,  families,  etc.,  is  the  endeavour  of  all  the  newer  text- 
books— for  instance,  the  great  joint  work  of  Engler  and  Prantl :  Die 
naturlichen  Pflanzenfamilien.  See  also  Lotsy:  Vortrage  uber  botanische 
Stammesgesckichte  (so  far  2  vols.)  ;  E.  Stromer  v.  Reichenbach : 
Lehrbuch  der  Paldontologie  (so  far  1  vol.) ;  F.  Broili  in  the  new  edition 
of  the  Grundzuge  der  Paldontologie  of  Zittel  (so  far  1  vol.).  The  great 
work  of  Zittel  and  Schenk  is  likewise  entirely  based  on  these  methods. 

K2 


132  THE  THEORY  OF  EVOLUTION 

has  been  already  said  applies  also  for  such  times  when 
the  organisms  in  question  had  the  best  opportunity  to 
demonstrate  their  evolutionary  capacity — for  instance, 
the  Pteridophytes  in  the  Carboniferous  age.  That 
the  life  conditions  at  that  time  were  the  most  favourable 
is  shown  by  the  great  number  of  individuals  and  species 
which  lived  together  and  successively  in  those  days. 

3.  Curious  fossil  forms  like  the  Graptolites,  the 
Trilobites,  Stegocephali,  the  great  Lizards  of  the 
Mesozoic  period,  among  the  animals,  and  the  Cordaites, 
Bennettites,  and  Pteridosperms  among  the  plants,  are 
to  be  regarded  as  really  extinct  forms.  Although  these 
may,  with  some  strain,  be  brought  in  between  two 
existing  classes,  they  do  not  become  absolute  '  links  ' 
in  the  sense  of  ancestral  intermediates.  They 
appear  and  disappear  as  Trilobites,  Stegocephali, 
Bennettites,  etc. 

How  entirely  unjustifiable  it  is  to  see  '  transitional 
forms  '  in  all  forms  which  cannot  be  identified  with  any 
recent  class  or  order  is  shown  by  the  few  remains  of 
some  formerly  widely  distributed  organisms.  In  the 
Mesozoic  age  the  Ginkgo  trees  form  for  the  time  the 
predominant  Gymnosperm  group ;  they  are  a  well- 
circumscribed  peculiar  group  on  account  of  the  singu- 
larity of  their  leaves — which  cannot  be  mistaken  for 
the  leaflets  of  our  Conifers  nor  for  the  gigantic  leaves 
of  the  Cycads  (the  two  other  main  forms  of  the  Gym- 
nosperms) — and  on  account  of  the  habit  of  their  stems. 
They  have  remained  to  this  day  since  the  Permian  era 
as  they  were.  What  descendants  of  these  should  we 


DOMAIN   OF   EVOLUTIONARY  HYPOTHESIS    133 

have  sought  for  among  our  Conifers  or  Phanerogams, 
if  the  solitary  surviving  species,  GinJcgo  biloba,  had  also 
become  extinct  and  had  been  buried  in  some  inaccessible 
place  or  had  not  become  known  to  Europeans  as  still 
existing  ? 

What  would  have  arisen  from  the  Rhyncocephali  of 
the  Permian  system,  or  from  the  Nautiloids  and  Crinoids 
if  they  had  been  more  numerously  preserved,  we  can 
easily  presume  from  Hatteria  (Sphenodon  punctata)  and 
the  few  Nautili  and  Crinoids  which  are  still  living. 
They  would  have  remained  the  orders  of  Rhyncocephali, 
etc.,  as  in  fact  is  the  case  with  the  only  Hatteria  which 
represents  the  entire  value  of  the  order 1  (Rhyncocephali) 
with  its  widely  branched  relatives  of  the  past. 

As  it  occurs  to  no  investigator  to  regard  the  present 
Hatteria  as  an  actual  transition  from  the  Newt  (which 
it  most  resembles)  to  the  Crocodile,  just  so  is  no  one 
justified  in  regarding  the  Permian  Rhyncocephali  as 
phyletic  linking  forms,  as  still,  however,  always  happens.3 

The  same  remark  applies  to  the  Permian  Stego- 
cephali,  which  for  the  time  being  are  only  known  as 
'  Stegocephali '- — i.e.  as  animals  which,  like  the  Amphibia, 
possessed  a  free  living  larval  form  and  two  occipital 

1  Hatteria  punctata  forms  in  the  textbooks  the  order  of  the  Rhynco- 
cephali, although  to-day  it  possesses  the  systematic  value  of  a  good  species. 
Ginkgo  biloba  represents  in  the  botanical  system  an  entire  class,  although 
all  the  still  existing  individuals  are  so  alike  that  they  only  form  one 
systematic  species. 

2  R.  Hertwig  says,  for  instance,  in  his  textbook,  p.  590  :    '  In  the  same 
way  the  "  Rhyncocephali  "   lead  also  to  the  Hydrosaurians,  particularly 
to  the  Crocodiles,  since  a  double  cheek-bone  exists  (jochbogen),  and  the 
"  quadratum  "  is  firmly  attached  to  the  skull.' 


134  THE  THEORY  OF  EVOLUTION 

bosses,  but,  with  these,  reptilian-like  teeth  and  a  scaly 
covering,  since  of  an  actual  connection  of  our  recent 
reptilian  orders  with  the  Permian  or  later  Stegocephali 
nothing  is  known.  Suppositions  might  be  permissible 
if  the  evolution  for  similarly  varied  animal  groups 
(as  are  the  present  Reptilia  and  those  Stegocephali) 
were  demonstrated  or  at  least  were  shown  to  be  very 
probable. 

Deperet  chastises  excellently  this  f  method  of 
approximate  estimation/  It  consists  therein  that  for 
a  genus  of  living  or  recent  animals,  whose  genealogy  it 
is  desired  to  ascertain,  several  other  genera  are  selected 
from  the  series  of  earlier  geological  periods  which  present 
a  certain  analogy  to  the  first  in  the  structure  of  an 
organ  or  in  a  small  number  of  organs.  With  the  aid 
of  these  genera  a  series  is  arranged  which,  with  regard 
to  the  changes  of  the  organs  taken  into  consideration, 
appears  to  fit  in  with  natural  evolution.  For  the  Mam- 
malia, for  instance,  there  is  taken  as  the  touchstone, 
sometimes  the  structure  of  the  molars,  sometimes  the 
canines,  here  the  progressive  regression  of  the  side 
toes,  and  there  the  graduated  development  of  the 
nasal  bones,  the  horns,  or  antlers,  while  the  rest  of  the 
organization  is  almost  entirely  neglected.  '  Further- 
more, the  chronological  order  of  the  appearance  of  the 
fossil  forms,  which  are  serially  arranged,  does  not  cause 
over-much  embarrassment  in  these  cases/  Thus  have 
Gaudry  and  Boule,  in  constructing  the  pedigree  of  the 
Urcidse,  between  the  Hyaenarctos  out  of  the  upper 
Miocene  and  the  first  Bears  (Ursus)  out  of  the  Pliocene, 


DOMAIN   OF  EVOLUTIONARY  HYPOTHESIS    135 

placed  a  still  living  genus — the  Aeluropus  (from  China) — 
because  this  animal,  with  regard  to  the  advanced 
development  of  its  molars,  represents  a  transitional 
grade  between  the  two  genera  which  it  is  endeavoured 
to  connect  together.  Such  anachronisms  are  to  our 
mind  quite  inadmissible. 

The  same  anachronism  everyone  is  guilty  of  who 
inserts  the  still  living  Rhyncocephalia  (Hatteria)  in 
the  same  way,  not  only  between  genera,  but  between 
two  orders  (Newts  and  Crocodiles),  as  a  connecting  link. 

4.  Furthermore,  the  actually  established  continuous 
reduction  of  the  sexual  generation  in  the  higher  plants, 
determined  by  comparative  botanists  and  advancing 
from  the  Ferns  to  the  Angiosperms,  does  not  prove 
by  itself  alone  that  Ferns,  Gymnosperms,  and  Angio- 
sperms form  a  genetic  series.  This  is  because  also  within 
the  Pteridophytes  themselves  there  is  determined  a 
similarly  increased  reduction,  if  we  assume  a  suitable 
association — i.e.  one  which  is  based  upon  this  character. 
From  the  macrospores  of  the  Water  Ferns  (e.g.  Salvinia) 
there  is  produced  a  very  small  female  prothallus  which 
no  longer  leaves  the  spore  integument ;  the  microspores 
even  only  form  a  pair  of  cells  ;  *  they  are  therefore,  so  far 
as  reduction  is  concerned,  not  behind  the  Gymnosperms. 
Nevertheless,  the  Water  Ferns  remain  true  non-seed- 
bearing  plants,  since  the  macrospores  are  thrown  off 
before  the  formation  of  the  embryo  and  therefore  do 
not  leave  the  mother  plant  as  a  so-called  seed. 

*  JS.  Warming  :  Handbuch  der  systematischen  Boianik,  p.  144. 


136  THE  THEOEY  OF  EVOLUTION 

Even  within  the  class  of  Club-mosses  a  similar 
procedure  is  to  be  observed.1 

Heterospory  finally — i.e.  the  peculiarity  of  forming 
small  and  large  spores  for  separated  male  and  female 
prothalli  (which  has  been  regarded  as  a  progressive 
stage  in  the  evolution  of  the  whole  plant  world) — is  found 
in  the  most  varied  plant  groups  ;  there  are  homosporous 
(with  spores  of  only  one  kind)  and  heterosporous  forms 
among  the  Ferns — the  Equisetae  and  the  Club-mosses. 
The  present  EquisetaB  are  even  exclusively  homosporous 
(therefore  '  lower ')  forms ;  the  Calamariaceae  were 
heterosporous. 

Thereby  is  it  demonstrated  by  evidence  that  differ- 
ences in  the  spore  formation  and  reduction  of  the  sexual 
generation  are  not  phenomena  which  by  themselves 
can  be  taken  as  transitional  stages  towards  other 
'  types  '  or  as  constituting  a  general  higher  formation.3 

5.  On  whatever  principles  we  may  proceed  in  the 
systematic  classification  of  the  present  organisms, 
so  far  we  always  arrive  at  the  result  that  the  plants 
and  animals  fall  into  a  few  larger  groups  which  exist 
separately  but  close  to  each  other.3  Are  these  groups 
also  really  types,  i.e.  primary  animal  and  plant  forms  ? 

1  E.  Warnung  :    Handbuch  der  systematischen  Botanik,  p.  153. 

2  J.  Reinke  agrees  to  this  when  he  says  (Einleitung  in  die,  fheoretische 
Biologie,  p.  471) :  '  If  in  this  sketch  I  have  put  forward  the  results  of  com- 
parative examination,  without  further  remarks,  as  evidence  of  the  genetic 
connection  (between  Ferns,  Gymnosperms,  and  Angiosperms)  of  phylo- 
genetic  evolution,  the  reader  will  not  be  in  doubt  with  regard  to  the 
manifold  hypothetical  elements  in  this  partly  fanciful  description.' 

3  With  regard  to  the  various  botanical  divisions  see  the  very  instructive 
chapter  on  the  Stdmme  des  Pflanzenreiches  by  Kerner  v.  Marilaun  (Pflanzen- 
leben,  II,  p.  488.     This  chapter  is  not  in  the  second  edition. 


DOMAIN  OF  EVOLUTIONAKY  HYPOTHESIS      137 

At  present  we  can  only  say  so  much  :  viz.  that 
those  plant  and  animal  groups  (families)  which  not 
only  now  but  also  during  the  whole  of  their  ancient 
existence  have  remained  alike  in  definite  characters 
peculiar  to  themselves — these  we  must  regard  as  types. 

In  this  connection  it  is  immaterial  what  rank  they 
are  given  in  the  present  classification,  whether  they 
form  species,  genus,  family,  order,  class,  or  stock.  Ginkgo 
biloba  is  to-day  a  species,  since  all  the  individuals  are 
entirely  alike ;  but  according  to  the  above  criteria  it  is 
a  type.  That  is  recognized  in  systematic  classification 
itself,  since  it  ranks  Ginkgo  biloba  as  a  '  class  '  in  con- 
sideration of  its  peculiarities  in  comparison  with  other 
Gymnosperms. 

Hatteria  forms  a  genus  with  several  species,  which, 
however,  differ  but  little  ;  its  peculiarities,  however, 
raise  its  position  to  that  of  an  order,  so  soon  as  it  is 
compared  with  other  (in  a  wide  sense)  similar  animals 
(Reptilia),  and  so  on. 

It  is  the  object  of  palaeontology  and  biology  to 
determine  the  number  of  fundamental  forms  of  animals 
and  plants.  The  task  is  difficult,  since  we  know  how 
much,  for  instance,  parasitism,  adaptation  to  other 
habitats,  and  transition  to  sessile  modes  of  existence, 
can  influence,  alter,  increase,  or  decrease  the  habit  and 
the  degree  of  differentiation. 

One  thing  certainly  already  appears  now  to  be  as 
good  as  certain,  viz.  that  at  least  some  fundamental 
forms  in  the  animal  and  plant  world  are  firmly  retained ; 
for  this  reason  an  attribution  of  all  animals  and  all 


138  THE  THEORY  OF  EVOLUTION 

plants  to  one  fundamental  form  is  '  extremely  unlikely  ' 
to  be  correct,  as  all  investigators,  so  long  as  they  are 
'  exact/  will  willingly  allow. 

It  would  be  well  if  in  every  evolutional  hypothesis 
these  suggested  limitations  were  adhered  to.  There 
still  remains  a  wide  field  for  research,  and  especially 
the  question  whether  and  how  the  types  were  established 
within  their  limits,  and  what  they  were  before  they 
appeared  as  completed  types  which  would  be  preserved 
for  us  and  perhaps  could  alone  be  preserved.  Should, 
for  instance,  the  Ferns  represent  a  true  type,  yet  that 
is  not  to  say  a  priori  that  the  plants  which  we  call 
Ferns  were  always  so  constituted.  One  thing  alone 
seems  fairly  certain.  '  Ferns  '  are  and  were  always 
different  from  Equisetums,  or  '  Invertebrates  '  show  no 
genetic  connection  with  Vertebrates,  or  Vertebrates 
were  never  such  Invertebrates  as  we  know  them.1 


i  Reinke  agrees  with  this  quite  emphatically.  In  his  book,  Die  Welt 
ah  Tat,  p.  351,  he  says  :  '  It  is  of  the  greatest  significance  that  in  the  multi- 
formity of  forms  almost  unlimited  types  appear.  These  types  embrace  the 
enormous  number  of  the  now  living  plants  and  animals  and  those  which 
have  reached  us  as  fossils.'  On  p.  352  he  continues  :  '  I  quote  here  a  palseon- 
tological  fact,  which  is  of  the  greatest  importance  for  the  theory  of  descent. 
While  we  find  in  the  petrifactions  of  the  Palaeozoic  and  Mesozoic  periods 
not  only  other  species,  but  also  a  preponderance  of  other  genera  than  at 
present,  yet  according  to  the  evidence  of  the  remains  found  there  has 
never  been  discovered,  even  in  the  oldest  periods,  any  other  main  type  of 
animal  or  plant  than  what  we  have  in  the  present  age.  Genera  and  species 
have  become  extinct  and  been  replaced  by  others.  Yet  the  fundamental 
types  have  survived  from  the  time  of  the  oldest  formations  to  the  present 
day.'  The  acceptance  of  a  polyphyletic  evolution — i.e.  of  varied  developed 
series,  separated  from  the  commencement — becomes  more  and  more  the 
dominant  opinion.  0.  Hertwig,  Reinke,  Kerner  v.  Marilaun,  Steinmann, 
Zittel,  Deperet,  Koken,  Wasmann,  and  others  regard  this  as  the  only 
admissible  view  or  at  least  as  the  most  probably  correct  one, 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      139 

Appendix :  Are  there  '  higher '  and  '  lower '  types  ?— 
In  the  Biologischen  Zentralblatt  (Nos.  1  and  2, 
1911)  B.  Franz  published  a  long  article  under  the 
title  '  Was  ist  ein  hoherer  Organismus  ? '  Franz 
concedes  in  the  first  place  that  the  opinion,  that 
there  are  various  high  grades  of  development  of 
animals  and  plants,  and  that  '  man  represents  the 
highest  grade  of  organic  evolution/  has  been  held 
essentially  unchanged  throughout  the  whole  period 
of  biological  research  since  the  time  of  Aristotle 
(p.  1).  Then,  however,  he  says  (p.  2)  that  all  our 
ideas  as  regards  high  and  low  in  the  organic  kingdom 
are  perfectly  objectless.  This  so  far  had  certainly 
been  recognized  by  only  three  biologists  (p.  2). 

On  page  3  it  is  stated  '  that  the  assumed  higher 
organism  is  neither  more  perfect  than  the  assumed 
lower,  nor  in  principle  is  it  distinguished  from  it  by 
additions  or  differentiations  as  of  higher  grade  than 
the  lower  .  .  .  wherefore  it  is  best  henceforth  to 
avoid  entirely  the  misleading  expressions  "  higher  " 
or  "  lower  "  organization,  "  more  perfect  "  or  "  less 
perfect,"  etc.,  in  biological  parlance/  The  author  will 
certainly  not  succeed  in  establishing  this  idea,  and 
the  number  of  his  disciples  who,  in  the  vanquishing 
of  false  prejudices,  'go  far  enough'  (p.  2),  will 
certainly  not  far  exceed  the  three  aforesaid. 

Franz  arrives  at  his — as  he  himself  feels — extra- 
ordinary conclusion  because  he  confuses  purposeful 
(ZwecJcmdssig)  and  perfect  (VolJcommen).  We  will 
therefore  at  least  explain  these  two  expressions. 


140  THE  THEOKY  OF  EVOLUTION 

What  Franz  understands  by  '  more  perfect '  (p.  5) 
he  indicates  by  taking  as  synonymous  the  following 
expressions:  '  more  favourable ;  better;  more  purposeful; 
adapted  in  a  higher  degree ;  more  capable  of  life  than 
the  lower.'  These  expressions  are  not  at  all  equivalent. 

A  thing — for  instance,  an  instrument — we  call  pur- 
poseful, useful  (Zweckmdssig  =  adapted  to  its  purpose),  if 
it  fulfils  the  objects  it  should  attain  to — viz.  its  purpose. 
The  old  church  clock  in  a  poor  village  is  useful  if  it 
only  strikes  the  hours  and  half-hours,  since  it  does  what 
it  can  and  must.  There  is  full  agreement  between  its 
construction  and  its  service  so  far  as  the  maker  has 
involved  this  in  its  works.  A  modern  chronometer 
which  in  a  whole  year  does  not  vary  one  minute  from 
astronomical  time,  which  shows  the  days  of  the  week 
and  month,  regulates  itself  automatically  against 
changes  of  temperature  or  humidity,  is,  considered 
by  itself,  no  more  purposeful,  since  it  only  furnishes 
what  is  instilled  into  its  mechanism ;  even  in  this 
case,  it  is  governed  only  by  simple  agreement  between 
construction  and  service. 

Nevertheless,  such  an  exact  chronometer  is  termed 
by  everybody  a  more  perfect  instrument  than  a 
mere  village  church  clock,  since  it  is  more  perfect, 
sufficing  in  a  more  purposeful  way  for  several  services 
instead  of  fewer  ;  it  is  more  perfect,  being  able  to 
indicate  exact  time  under  changing  circumstances 
instead  of  unchanging  ones  ;  it  is  more  perfect  since 
it  regulates  itself  instead  of  being  regulated  by  other 
means,  etc. 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      141 

Thus  '  perfection '  implies  suitability  to  purpose 
(Zweckmdssigkeit)  ;  its  higher  or  lower  grade  is 
determined  by  the  extent  of  the  services  which  are 
needed  to  be  rendered  simultaneously  and  purpose- 
fully, furthermore  by  the  exactness  and  rapidity  of 
the  fulfilment  of  the  inner  capacities. 

If  what  has  been  said  be  applied  to  organisms, 
many  difficulties  which  Franz  presents  disappear 
(see,  for  instance,  p.  9  re  land  vertebrates  and  fish). 

Those  animals,  therefore,  which  come  into  purposeful 
relations  with  more  external  objects,  and  have  more 
means  of  making  these  objects  useful,  are  more  perfect 
animals.  Man  is  therefore  the  most  perfect  being. 

There  is  no  form  of  organism  which  he  cannot  utilize : 
he  tames  the  beasts  and  cultivates  the  plants.  No 
inorganic  energy  escapes  his  service  if  he  needs  it. 
There  is  no  faculty  of  thought  which  he  has  not  increased 
by  suitable  instruments  in  order  to  come  into  pur- 
poseful connection  with  more  objects  which  other- 
wise would  elude  his  observation.  No  medium  has 
remained  inaccessible  to  him:  he  traverses  the  water 
and  would  make  the  air  his  own.  Thereto  will  Franz 
reply  that  these  be  intangible  '  values '  (Werthe).  Let  it 
be  called  what  one  will,  but  it  is  nevertheless  an  actual 
reality.  By  instruments  the  extent  of  the  purposeful 
relations  of  mankind  with  the  external  world  are  in 
fact  increased :  man,  therefore,  becomes  ever  more 
perfect.  These  relations  are,  furthermore,  to  a  large 
extent  necessary  so  that  he  may  preserve  his  life,  which 
is  also  something  real. 


142 


THE  THEORY  OF  EVOLUTION 


No  animal  and  no  plant  exhibits  such  a  multifarious 
purposeful  intercourse  with  surrounding  nature:  they 
are  all  confined  within  very  narrow  limits  to  definite 
objects  and  definite  conditions  of  life ;  they  are 
specialized  in  their  entire  construction,  i.e.  adapted  in 
one  direction,  which  is  the  direct  opposite  of  '  perfect ' 
(volJcommen). 

It  is  therefore  incomprehensible  when  Franz  (p.  36) 
writes :  '  It  appears  to  me,  for  instance,  that  by 
the  formation  of  the  intestinal  canal,  the  formation 
of  the  foot  and  the  arming  of  the  head,  the  Ruminants 
have  decidedly  assumed  a  similar  supreme  position 
(Gipfelstellung),'  as  has  man,  in  the  general  opinion, 
by  virtue  of  his  brain.  The  quadruple  divided  stomach 
of  the  Cow  and  the  horns  on  the  head  are  certainly  very 
purposeful  instruments  for  a  strong  grass-eater  and 
an  otherwise  quite  unarmed  beast.  If  man  has  no 
specialized  formation  of  the  intestinal  canal,  what  he 
has  permits  other  nutrition  than  only  green  fodder, 
which  under  the  circumstances  is  very  much  to  the 
purpose  and  is  recognized  by  all  as  '  perfection/  As 
substitute  for  the  horns,  which  can  only  be  used  in 
close  combat,  he  has  known  how  to  provide  himself 
with  firearms,  or  traps,  as  opposed  to  which  even  the 
mighty  herds  of  the  Bison  have  at  last  had  to  yield. 
In  the  invention  and  manufacture  of  such  extremely 
and  vitally  purposeful  things  his  brain  has  done  him 
the  greatest  service.  His  weapons,  it  is  true,  do  not 
grow  upon  him,  as  do  the  horns  on  an  ox,  but  his  under- 
standing has  '  grown  '  instead,  and  the  gun  is  just  as 


DOMAIN  OF  EVOLUTIONARY  HYPOTHESIS      143 

much  an  existing  thing,  and  fulfils  in  reality  the  same 
service,  as  horns  upon  the  head. 

Certainly  of  '  consciousness '  (i.e.  of  psychic  capaci- 
ties and  a  suitable  conformation  of  brain),  as  criterion 
for  '  higher '  and  '  lower/  Franz  will  know  absolutely 
nothing.  This  he  expresses  thus :  '  All  disputation 
about  consciousness  in  animals  and  plants  has  remained 
so  far  not  only  hypothetical  but  unsatisfactory.  .  .  . 
Therefore  every  objection  based  on  consciousness  I 
decline  to  meet  as  being  outside  discussion '  (p.  11). 
Franz  in  this  treats  the  matter  really  too  easily.  Such 
procedure  can  never  lead  to  the  establishment  of  the 
truth.  A  whole  series  of  investigators  have  occupied 
themselves  thoroughly  and  experimentally  with  the 
question  of  consciousness :  their  reasons  are  to  be  tested 
and  thereby  must  a  decision  be  arrived  at !  One 
thing  is  also  quite  undisputed,  viz.  that  man  in  any  case 
stands  high  above  all  animals  in  '  intelligence/  This 
truth  is  beyond  doubt  and  therefore  can  and  must  be 
regarded  as  the  criterion  of  his  '  highest '  position 
(CKpfelstellung),  since  the  intellect  provides  and  pro- 
vided mankind  with  actual  definable  aids  to  his 
existence  and  to  the  extension  of  his  purposeful 
relations  to  the  outer  world. 

B.  Franz  has  thus  shown  by  the  evidence  that  with 
all  organisms  of  the  present  and  the  past  there  is  a 
perfect  agreement  between  construction  and  function, 
between  needs  and  faculties,  in  order  that  they  be 
satisfied,  that  all  organisms  are  purposefully  arranged. 
On  the  other  hand  it  will  in  the  future  be  also  maintained 


144  THE  THEORY  OF  EVOLUTION 

without  hesitation  that  in  the  realm  of  the  living  there 
exist  the  most  manifold  grades  of  perfection,  for  it  is 
certainly  no  '  illusion '  (Tauschung)  if  '  in  the  case  of 
certain  organic  creatures  we  cannot  mentally  separate 
the  values  which  we  are  accustomed  to  associate  with 
their  existence  '  (p.  6).  '  More  perfect '  and  '  more  im- 
perfect '  instruments  there  will  always  be,  even  if 
both  kinds  of  tools  are  quite  well  fitted  for  their 
temporary  uses. 


SECTION  III. 
EVOLUTIONAEY   HYPOTHESES. 

CHAPTER  I. 

THE  PRINCIPAL  ATTEMPTS  AT  EXPLANATION  HITHERTO. 

MUCH  of  that  which  we  shall  say  in  the  following 
pages  regarding  the  evolutionary  hypotheses  already 
put  forward  has  only  an  historical  value.  An  oppor- 
tunity, however,  thereby  presents  itself  for  learning 
the  nature  of  the  evidence  by  which  it  has  been 
attempted  to  establish  the  theory  of  evolution  as 
opposed  to  that  of  constancy.  The  refutation  of  the 
theory  of  the  unchangeability  of  the  systematic  species, 
which  with  Lamarck  was  hardly  much  more  than  a 
simple  denial,  constitutes  the  one  permanent  result 
of  the  best  known  of  all  theories  of  evolution  termed 
Darwinism  and  Lamarckism. 

§  1.  Lamarckism  and  neo-Lamarckism* 
(1)  The  original  doctrine  of  Lamarck. 

(i)  Short  description. — Jean  Baptiste  Chevalier  de 
Lamarck  (1744  to  1829)  published  in  the  year  1809  a 
work  entitled  '  Philosophic  Zoologique/  in  which,  for 
the  first  time,  the  unchangeability  of  organisms  was 
entirely  denied,  and  the  development  of  the  present 
organic  world  from  inorganic  matter  by  spontaneous 


146  THE  THEOKY  OF  EVOLUTION 

generation  was  affirmed :  the  animals  from  gelatine 
masses,  the  plants  from  masses  of  mucus.  The  finest 
fluids  penetrate  these  masses,  make  them  soft  ( =  cellular) 
and  therefore  suitable  for  life.  Then,  according  to  a 
definite  plan  determined  by  the  great  Creator  of  all 
things,  there  followed  the  creation  of  ever  more  and 
more  complicated  forms. 

How  did  Lamarck  arrive  at  such  conclusions  ? 

In  the  first  place  it  appeared  to  him  unnatural  that 
the  successive  organic  worlds  (creations),  so  different 
from  each  other,  should  be  destroyed  by  general  cata- 
strophes and  then  again  replaced  by  a  new  creation  in 
altered  forms.  It  appeared  simpler  to  him  to  suggest 
that  the  separate  '  creations '  arose  genetically  from  each 
other.  The  variability  of  the  organisms — which  is 
certainly  the  premiss  of  all  evolution — he  sought  to  show, 
since  he  demonstrated  to  us  thoroughly  by  examples 
how  organs  can  alter,  though  not  that  they  do  so  in 
point  of  fact.  He  was  strengthened  in  his  opinion 
by  the  observation  of  the  similarity  of  the  organic 
groups,  which  was  most  easily  explained  by  a  common 
origin.  Furthermore,  it  struck  him  how  the  organs  of 
the  animals  were  so  perfectly  adapted  to  quite  definite 
needs,  to  a  narrowly  limited  mode  of  existence.  The 
idea  appeared  to  him  to  be  closely  associated  that  it 
was  just  these  needs  which  must  be  the  cause  that  the 
organs  are  precisely  so  constituted,  often  in  a  quite 
wonderful  and  peculiar  way.  Lamarck  then  attempts 
to  make  it  comprehensible  how  the  animals  could 
arrive  at  this  purposeful  constitution  of  their  organs, 


PRINCIPAL  ATTEMPTS  AT  EXPLANATION       147 

which  are  adapted  so  wonderfully  to  the  most  varied 
needs  of  existence,  even  to  the  smallest  detail.  That 
is  the  chief  idea,  and,  in  a  certain  sense,  also  the  greatest 
service  Lamarck  rendered  :  he  puts  forward  a  '  theory 
of  organic  purposefulness/  not  a  doctrine  of  descent, 
which  all  problems  of  the  '  history  of  life '  involve.1 

With  regard  to  the  origin  of  '  organic  purposefulness  ' 
he  writes  as  follows  : 

(  That,  in  the  first  place,  any  alteration,  even  incon- 
siderable, in  the  circumstances  in  which  each  race  of 
animals  finds  itself,  induces  an  actual  change  of  its 
requirements.  That,  in  the  second  place,  each  alteration 
in  the  requirements  of  the  animals  renders  necessary 
other  faculties  in  order  to  satisfy  these  new  requirements 
and  consequently  other  habits.  That  thereby  each 
new  requirement,  since  it  renders  necessary  new 
faculties  to  meet  it,  demands  from  the  animal  which 
experiences  it  either  the  extended  use  of  an  organ  of 
which  it  had  hitherto  made  less  use,  whereby  such 
organ  is  developed  and  considerably  enlarged,  or  the 
use  of  new  organs  to  which  the  requirements  within  it 
imperceptibly  give  rise  through  the  efforts  of  its  inner 
perception'  (Gefuhl)* 

An  example  may  explain  the  above  : 

1  That  we  really  perceive,  in  the  explanation  of  the  purposefulness  of 
the  organisms,  the  chief  merit  of  Lamarck,  is  shown  in  the  clearest  fashion 
by  the  work  of  the  Lamarckian  disciples.    Thus,  for  instance,  B.  M.  Pauly 
says  (Darwinismus  und  Lamarckismus,  Munich,  1905,  46) :    *  His  works 
[L.]  contain  a  theory  of  organic  purposefulness  that  ...  at  this  moment 
we  have  not  yet  risen  above.' 

2  See  Dr.  A.  Wagner :   Geschichte  des  Lamarckismus,  Stuttgart,  1909, 
p.  32. 

L2 


148  THE  THEORY  OF  EVOLUTION 

'  The  bird,  whose  needs  attract  it  to  the  water  in 
order  to  seek  its  food  therein,  spreads  its  toes  apart 
when  it  desires  to  strike  the  water  and  swim  upon  its 
surface.  The  skin  which  unites  the  toes  at  their  base 
acquires,  by  this  unceasingly  repeated  extension  of  the 
toes,  the  habit  of  spreading  itself  out.  Therefore  in 
time  the  broad  swimming  webs  arise  which  at  present 
connect  the  toes  of  Ducks,  Geese,  etc.  These  efforts 
to  swim — i.e.  to  strike  the  water  in  order  to  progress 
in  this  liquid  and  move  therein — have  also  broadened 
the  toes  of  the  Frog,  the  Sea  Tortoise,  the  Fish  Otter, 
the  Beaver,  etc/ L  Lamarck  thus  attributes  the 
purposefulness  of  the  organisms  to  their  striving 
towards  the  purpose  concerned  !  His  doctrine  is  a 
fiDal  (finalistisch)  one. 

Everything  that  the  animals  newly  acquire  in  this 
manner  is,  according  to  Lamarck,  inherited  by  the 
offspring  and  thus  becomes  ever  more  and  more  fixed. 

(ii)  Criticism. — (a)  We  accept  much  of  what  Lamarck 
says,  but  not  always  for  his  reasons.  If  the  cata- 
strophic theory  be  denied,  as  in  itself  an  improbable 
idea,  then  we  must  also  reject  the  unchangeability  of 
species.  In  our  Introduction  we  have  entered  into 
details  regarding  this. 

It  is  also  correct  that  the  organisms  must  alter 
themselves  if  an  adaptation  to  changed  environments 
generally  be  effected.  (In  contradiction  to  Darwin, 

1  Geschichte  des  Lamarckismus,  p.  35.  Many  other  similar  examples  are 
given.  The  most  remarkable  and  most  popularly  known  examples,  which 
Wagner  does  not  mention,  are  those  of  the  Kangaroo  and  Giraffe.  Philos. 
Zool.,  chap.  vii.  :  Influence  des  circonstances  sur  les  actions  des  animaux. 


PRINCIPAL  ATTEMPTS  AT  EXPLANATION       149 

according  to  whom  it  is  the  individuals  which  by  chance 
are  better  fitted  which  survive.) 

(b)  On  the  other  hand  the  acceptance  of  spontaneous 
generation,  independently  of  the  philosophical   impos- 
sibility, is  a  serious  methodological  error.     Everything 
that    we    observe  —  and    every    hypothesis    must    be 
based  on  that — speaks  against  spontaneous  generation 
(see  above,  p.  96). 

(c)  The  idea  which  Lamarck  has  formed  regarding 
the  process  of  the  new  formation  of  separate  organs, 
cannot  a  priori  be  disproved.     Lamarck,  however,  at 
the  most  explains  how  many  birds  acquire  swimming 
webs,  long  necks,  climbing  claws,  etc.  ;    he  does  not, 
however,  explain  at  all  how  these  animals    arrived  at 
the    general    organic    type    of    e  Birds ' :   since    before 
they  acquired  swimming  webs,  etc. — i.e.  a  part  of  the 
entire    organism    adapted    to    definite    services — they 
were  already  birds.      The  same  applies  to  the  other 
'  types '   which   we    term    families  and  classes.     They 
are    now    sharply    separated    from    each    other    and, 
according    to    palseontological   evidence,  were   always 
so ;    they   must    therefore  be   regarded  as  a    (  given  ' 
something — not  as  something  which  has    ( happened  ' 
(geworden). 

Certainly  Lamarck,  at  least  according  to  his  words, 
regards  the  whole  development  as  due  to  a  plan  of  the 
Creator.  Therefore  we  must  assume  that  either  from 
the  beginning  or  from  a  very  early  period  the  said  types 
were  established  in  the  primary  forms,  so  that  every 
further  development  should  occur  within  the  limits 


150  THE  THEOKY  OF  EVOLUTION 

determined.     Thus   can    Lamarck   explain   the    origin 
and  preservation  of  the  types. 

Some  modes  in  which,  according  to  palaeontology,  the 
formation  of  differently  constructed  organic  forms  pro- 
ceeded— viz.  increase  of  size,  specialization,  regression — 
can  certainly  be  partially  explained  as  Lamarck  proposes. 

(2)  N eo-Lamarckism. 

(i)  Statement. — We  have  seen  how  Lamarck  ex- 
plained organic  adaptation.  He  ascribed  to  the  organism 
itself  the  faculty,  in  the  first  place,  of  recognizing  in 
some  way  the  newly  arising  requirements,  of  perceiving 
such,  and  then,  by  willed  and  conscious  (?)  efforts,  of 
meeting  the  new  needs  and  altering  the  organs  con- 
cerned in  a  purposeful  manner.  The  adaptation  to 
a  purpose  which  we  now  see  completed  before  us  is 
thus  the  result  of  striving  towards  the  purpose  by  the 
organism  itself  :  it  is  a  self-adaptation. 

This  self-adaptation  Darwin  has  denied,  and  in  its 
place  put  the  survival  of  such  as,  by  chance,  are  the 
fittest.  That  was  a  mighty  retrograde  step  as  con- 
trasted with  Lamarck,  as  is  gradually  more  and  more 
recognized.  The  natural  historians  and  philosophers 
who  in  the  last  few  years  have  again,  in  large  numbers, 
reverted  to  Lamarck's  ideas,  term  themselves  neo-La- 
marckians  and  partly  as  of  the  ( psychobiological  school/1 

1  As  their  chief  representatives,  who  also  have  published  formal  pro- 
grammes, we  may  mention  :  A.  Pauly  (Darwinismus  und  Lamarckismus), 
A.  Wagner  (Der  neue  Kurs  in  der  Biologie),  the  GescMchte  des  Lamarckismus, 
and  some  smaller  writings.  R.  H.  Franc 5  (Das  Leben  der  Pflanze.,  Stuttgart, 
1905-1908)  cannot  be  placed  on  the  same  level  as  the  other  investigators 
named,  despite  Professor  Wagner's  defence. 


PRINCIPAL  ATTEMPTS  AT  EXPLANATION       151 

What  was  good  in  Lamarck's  doctrine  was  taken 
over  by  the  neo-Lamarckians  and  defended  as  victorious 
over  materialism  in  general  and  Darwinism  in  particular 
—viz.  the  doctrine  of  '  Autoteleology '  of  the  organisms, 
as  it  is  now  called. 

If,  however,  neo-Lamarckism  be  regarded  as  a 
theory  of  evolution,  it  is  a  terrible  mixture  of  assump- 
tions and  postulates  without  any  comprehensible  basis 
at  all.  Nowhere,  whether  in  the  works  of  France, 
Pauly,  or  Wagner,  do  we  find  any  thorough  presentation 
of  the  results  of  palseontological  research.  In  its  place 
they  put  forward  as  their  chief  argument  the  phrase, 
that  evolution  must  embrace  indiscriminately  every- 
thing— man,  animals,  and  plants — all  of  which  have 
been  evolved  from  common  ancestors. 

This  they  demonstrate  thus  : 

The  similarity  of  the  organisms,  especially  with  regard 
to  the  '  psyche/  which  alone  renders  possible  and  guides 
the  evolution,  must  be  explained  by  a  common  origin. 

Now,  however,  all  living  beings,  and  perhaps  also  the 
so-called  inorganic  bodies,  possess  a  '  psyche/  and  one 
provided  with  faculties  of  recognition,  effort,  and  decision. 
These  faculties  are  naturally  not  of  the  same  perfection 
in  plants,  animals,  and  man,  but  are  in  no  way  essen- 
tially different  from  each  other.  The  '  psyche '  of  plants, 
animals,  and  man,  presents  therefore  a  single  series  in 
which  the  fundamental  peculiarities  of  all  organisms— 
(viz.  decision  and  will) — are  gradationally  perfected. 
They  are  therefore  similar,  especially  in  the  'psyche/ 
the  basal  factor  of  all  evolution. 


152  THE  THEOKY  OF  EVOLUTION 

Since,  now,  each  similarity  which  consists  in  the 
possession  of  one  and  the  same  perfection,  although 
in  different  degrees,  must  be  explained  by  a  common 
descent,  therefore  man,  animals,  and  plants  have  arisen 
from  each  other  or  from  common  ancestors.1 

(ii)  Criticism. — (a)  The  main  argument  of  the  neo- 
Lamarckians  is  the  assumption  a  priori  that  similarity, 
quite  generally  and  without  any  limitation,  depends 
on  descent.  That,  however,  is  false,  and,  in  the  sense 
which  is  imputed  to  this  assumption  by  the  psycho- 
biological  school,  utterly  impossible. 

Proof. — We  have  already  shown  thoroughly    that 


1  It  has  not  been  easy  for  us  to  frame  an  argument  in  forma  from  the 
programme  writings  of  France,  Pauly,  and  Wagner.  Often  we  stand 
simply  helpless  before  such  expressions  as  the  following,  in  which  France 
endeavours  to  make  us  '  comprehend  '  the  existence  of  the  plant  soul 
(see  Wagner,  Gesch.  d.  Lamarckismus,  p.  202) :  '  The  psychic  working 
principle  in  plants  has  so  far  repeatedly  shown  itself  to  be  of  very  re- 
stricted powers.  It  will  be  well  always  to  emphasize  this  point,  since 
it  is  precisely  thereby  that  the  objection  regarding  the  unjustified  human- 
izing (Vermenschlichuung)  of  plant  actions  is  in  advance  struck  upon  the 
head.'  Nevertheless  he  proceeds  :  '  that  they  [actions  of  men  and  plants] 
are  alike  in  principle,  which  permits  the  conclusion  that  they  are  of  like 
origin.  Therefore  the  chief  characteristic  of  the  plant  and  cell  souls 
is  the  narrowness  of  their  judgments,'  or  in  other  words,  '  the  many  failures 
and  the  manifold  stupidities  which  are  found  in  plant  life.' — *  Plants  can 
be  easily  deceived,  and  movements  may  be  caused  the  futility  of  which 
is  easily  seen  by  our  thought  but  not  by  that  of  the  plant.'—'  Our  brain 
cells  see  through  the  stupidity  of  our  body  cells  because  their  powers  of 
judgment  stand  higher.  .  .  .  They  have  learned  to  do  so  because  from 
the  beginning  they  have  never  done  anything  else  than  to  practise  them- 
selves in  judging  and  thinking,  while  those  (the  body  cells),  as  the  common 
working  horde,  also  had  to  devote  themselves  to  varied  handiwork.  This 
affords  us  the  particular  key  to  the  spiritual  constitution  of  the  plant.  [?] 
The  poor  thing  can  only  think  with  body  cells  ;  it  has  no  special  thinking 
organ  and  has  therefore  been  sent  to  the  bottom  of  the  class  in  the  school 
of  life.' 


PRINCIPAL  ATTEMPTS  AT  EXPLANATION       153 

only  specific  similarity  is  determined  by  common 
descent,  as  actual  practical  observation  shows.  Palaeon- 
tology certainly  renders  it  probable  that  also  fairly 
different  animals  may  descend  from  common  ancestors. 
This  difference  was  acquired  through  differentiation 
and  specialization,  but  always  within  narrow  limits. 
Never,  however,  do  the  fossils  found  demand  the 
assumption  that  a  higher  class  arose  from  a  lower 
one,  to  say  nothing  of  one  family  arising  from  another, 
or,  in  the  extreme,  animals  from  plants. 

(b)  That  the '  psyches '  of  man,  the  animals  and  plants, 
are  only  a  perfection  of  the  same  fundamental  faculties 
of  all  organisms  is  altogether  false.  In  the  first  place 
the  soul  of  man  and  also  those  of  animals  and  plants 
cannot  be  regarded  as  (  perfections  '  of  matter :  they 
are  substantial  components  of  the  organisms.  There 
is  an  essential  difference  between  a  '  psyche  '  which 
thinks  and  shows  a  free  self-determination  (the  human 
soul)  and  one  whose  faculties  do  not  extend  beyond 
the  provision  of  sensitive  recognition  and  sensitive 
endeavour  (the  animal  soul).  With  us  the  senses  do 
not  suffice  for  thought  and  free-will,  nor  do  they  with 
animals,  and  never,  really  never,  is  there  to  be  observed 
anything  of  the  sort  with  them.  Has  not  the  entire 
modern  animal  psychology  been  written  also  for 
the  psychobiologists  ?  (Wundt,  Thorndike,  Hobhouse, 
Morgan,  Stumpf,  Wasmann). 

The  same  applies  to  the  difference  between  animal 
and  plant  souls.  That  plants  respond  to  the  same 
external  stimuli  otherwise  than  do  inorganic  bodies, 


154  THE  THEORY  OF  EVOLUTION 

that  they  can  adapt  themselves  thereto,  etc.,  shows 
that  they  are  something  essentially  higher  than  mere 
matter  and  even  than  a  machine.  That  they  have 
power  of  recognition  and  conscious  power  of  effort,1 
is,  however,  contrary  to  experience,  which  by  all  criteria 
shows  that  the  plants  do  not  sensibly  recognize,  feel, 
and  will  (see  above,  p.  108). 

In  the  animals,   however,   together  with   the  self- 

1  This  Haberlandt,  upon  whom  we  quite  particularly  depend,  has 
also  not  shown.  What  Haberlandt,  by  his  classical  studies,  has  contributed 
thereto  is  stated  by  Wagner  (Geschichte  des  Lamarckismus,  p.  145),  viz., 
'  direct  capacity  of  adaptation  of  the  plants,  power  of  self-construction, 
correlative  influence  in  the  formation  of  tissues,  the  control  of  the  entire 
plant  body  in  its  finer  and  coarser  construction  through  the  function.' 
All  this  was  exactly  taught  by  the  Christian  philosophers,  often  in  quite 
the  same  words.  They  therefore  ascribe  a  soul  to  the  plants,  but  cer- 
tainly not  one  acting  with  consciousness,  since  all  expressions  thereof  are 
lacking. 

That  we  are  not  forced,  therefore,  to  ascribe  to  the  plants  (and  animals) 
'  judgment,'  '  thought,'  etc.,  no  one  other  than  Haberlandt  himself  has 
clearly  shown.  He  protests,  namely,  quite  recently,  against  the  exploitation 
of  his  words  and  experimental  results  by  Pauly,  France,  and  Ad.  Wagner 
(he  gives  the  three  names  himself)  in  the  following  significant  words  : 
'  If  the  results  of  the  newer  stimulus  physiology  and  sense  physiology  in 
relation  to  plants  are  brought  in  in  the  most  comprehensive  fashion  for  the 
foundation  of  a  psychobiology  and  plant  psychology  on  Lamarckian 
principles,  then  this  implies  an  advance  in  thought  which  is  not  justified. 
The  possibility  of  psychical  phenomena  in  the  whole  animal  and  vegetable 
kingdom  can  be  calmly  conceded,  without  in  the  very  least  degree  im- 
agining that  the  most  varied  self -regulations  of  the  organism,  and  physio- 
logical and  morphological  processes  of  adaptation  analogous  to  human 
efforts  towards  a  recognized  goal,  can  be  explained  teleologically  in  the 
strict  sense  of  the  word.'  (G.  Haberlandt :  Physiologische  Pftanzenanatomie, 
Leipzig,  1909,  569  A.I.) 

That  is  excellently  put.  But  Haberlandt  might  have  added  that  his 
investigations  do  not  justify  the  ascription  of  consciousness  to  plants 
generally,  nor  any  sensibility,  since  his  '  sense  organs  '  are  organs  for  the 
reception  of  special  '  stimuli '  and  nothing  else.  (See  his  8innesorgc>ne 
im  Pflanzenreich,  Leipzig,  1908,  and  Physiolog.  Pflanzenanatomie,  p.  520.) 
(See  above,  p.  112.) 


PRINCIPAL  ATTEMPTS  AT  EXPLANATION       155 

regulations,  adaptations,  etc.,  which  we  ascribe  to  the 
'  psyche '  of  plants  as  their  last  cause,  we  note  still  other 
faculties  which  remain  entirely  inexplicable  unless  there 
be  ascribed  a  power  of  recognition  and  of  spontaneous 
effort.  This  recognition  and  striving  power,  as  observa- 
tion teaches  us,  is  equal  or  similar  to  our  own  if  we 
act  as  thinking  beings,  but  incomparable  with  our 
intellectual  power  and  that  of  free-will. 

There  does  not,  therefore,  exist  that  continuity  of 
the  '  psyches '  of  plants,  animals,  and  man.  Thereby  fails 
the  main  argument — nay,  the  only  one — in  so  far  as 
neo-Lamarckism  would  be  a  general,  all-embracing, 
and  explanatory  hypothesis  of  evolution.1 

(c)  Neo-Lamarckism  may  explain  the  adaptive 
faculties  but  not  the  perfection  of  organization  of 
the  various  organic  types :  these  are  something 
'  given/  and  remain  so  during  the  whole  geological 
period  of  evolution. 

Webbed  feet,  long  necks  and  long  tongues,  climbing 
claws,  etc.,  may  be  explained  by  adaptation  through 
purposeful  efforts,  but  some  sort  of  neck  must  have 
been  possessed  already  by  the  animal;  and  to  some 
one  type  must  Bird,  Mammal,  and  Serpent  have 
previously  belonged. 

1  France  (Pflanzenpsychologie  als  Arbeitshypothese,  p.  23)  confesses  that 
neo-Lamarckism  (as  he,  Pauly,  Wagner,  and  others  represent  it)  stands  and 
falls  with  the  continuity  argument.  '  Our  working  hypothesis  rests  before 
all  on  the  argument  of  continuity.  It  stands  or  falls  with  the  doctrine  of 
Evolution.  [(?)  This  should  be  :  '  stands  .  .  .  with  this  argument ' ;  since 
with  the  doctrine  of  evolution  as  a  fact  would  fall,  it  might  be  assumed, 
every  evolutional  hypothesis  (as  an  explanation).]  The  plant  descends  from 
the  same  original  being  from  which  man  also  has  been  evolved.' 


156  THE  THEORY  OF  EVOLUTION 

How  did  the  organisms  arrive  at  these  constructive 
plans  ? 

That  appears  to  Wagner  himself,  who  otherwise, 
once  at  least,  ridiculed  '  types '  and  '  constructive 
plans/  to  be  a  difficult  problem :  '  It  appears  to  be 
a  very  difficult  problem,  perhaps  the  most  difficult  in 
the  whole  evolutional  doctrine  ' l — and,  as  we  can  add, 
a  problem  decided  for  the  time  being  by  palaeontology 
against  Wagner,  since  the  organic  types  do  not  develop 
the  one  from  the  other — they  are  simply  there. 

Despite  the  evident  methodological  errors — it  is, 
as  an  evolutional  hypothesis,3  a  purely  theoretical 
construction  a  priori— and  despite  the  actual  errors 
(re  the  psyche),  we  have  discussed  neo-Lamarckism 
more  in  detail  because  it  appears  to  be  destined  in  the 
next  decades  to  become  the  credo  of  the  neonistic  and 
atheistic  evolutional  theorists.  All  too  long  it  will 
not  triumph,  since  its  fundamental  opinions,  to  which, 
according  to  Wagner  and  France  at  least,  atheism  3 
contributes,  will  never  be  the  common  property  of 
mankind. 

1  A.  Wagner  :   Geschichte  des  Lamarckismus,  p.  231. 

2  Wagner's  book  (and  also  that  of  Pauly  and  France)  is  really  a  defence 
of  vitalism  against  materialism — e.g.  Darwinism — and  in  this  connection 
he  does  excellent  work  in  some  parts  of  the  book.     '  Evolution  '  only  plays 
a  role,  in  so  far  as  '  Pan-psychism  '  is  the  principle  from  which  the  history 
of  evolution  can  be  deduced.     Wagner  says  this  distinctly  (Geschichte. 
d.  Lamarck..,  p.  127). 

3  In  an  altogether  hostile  fashion  Wagner  polemically  attacks  (see 
above  work)  the  belief  in  God    and   divine  intervention  in  evolution  ; 
all  such  things  are  to  him  '  belief  in  miracles,  mysticism,  and  metaphysics.' 


PRINCIPAL  ATTEMPTS  AT  EXPLANATION       157 

§  2.  Darwinism    and    neo-Darwinism. 
(1)  Darwinism. 

(i)  Darwin's  Doctrine. — Charles  Robert  Darwin,  as 
scientific  associate,  accompanied  an  expedition  to 
America  on  board  the  Beagle  in  the  year  1831.  Two 
observations  which  he  made  there  gave  him  particular 
food  for  thought.1 

In  the  plains  of  La  Plata  and  Patagonia  he  discovered 
fossil  remains  of  gigantic  Sloths  (Edentata = toothless), 
especially  of  Dasypus  gigas.  Might  not  the  small  living 
forms  of  the  Sloth,  which  are  now  exclusively  found 
in  South  America,  be  the  offspring  of  those  gigantic 
forms  ?  In  that  case  they  would  certainly  have  been 
considerably  altered. 

The  farther  he  went  from  North  to  South,  so  much 
the  more  it  struck  him  how,  particularly  the  Birds 
(he  was  an  ornithological  expert),  but  also  other  animals, 
gradually  assumed  a  somewhat  different  appearance. 
Might  not  this  difference  be  a  simple  result  of  somewhat 
changed  environments  ?  In  that  case  the  organisms 
were  again  variable,  and  again  this  was  due  to  the 
influence  of  external  environmental  conditions. 

Full  three  and  thirty  years  he  employed  after  his 
return  (1836)  in  experimenting — that  is,  by  breeding— 
to  demonstrate  the  variability  of  organisms  and  discover 
the  principle  by  which  this  variability  was  governed  in 

1  See  as  regards  the  following  remarks  the  excellent  report  of  R.  de 
Sinety,  S. J. :  Un  demi-siecle  de  Darwinisms  (Revue  des  Questions  scientifiques, 
1910). 


158  THE  THEORY  OF  EVOLUTION 

nature  in  order  to  produce  ever  better  adapted  and 
higher  forms. 

Since  in  nature  man  does  not,  as  in  breeding 
experiments,  supervise  the  selection  and  thereby  fix 
a  desired  change,  he  consequently  sought  another 
selective  factor,  and  found  it  in  the  so-called  '  natural 
selection/  He  published  his  opinions  in  the  well- 
known  book  '  Origin  of  Species  by  Means  of  Natural 
Selection  :  or,  the  Preservation  of  Formed  Races  in  the 
Struggle  for  Life'  (1859),  and  'The  Descent  of  Man5 
(1871). 

The  progeny  of  the  same  parents  are,  according 
to  him,  never  perfectly  like  the  parents  or  each  other  : 
there  are  always  differences,  favourable  or  unfavourable, 
among  the  individuals  concerned.  All  the  progeny 
cannot  survive  :  if  we  think  of  the  thousands  of  seeds 
which  a  single  plant  can  produce,  only  those  which, 
by  chance,  are  more  favourably  constituted  have  a 
prospect  of  preservation  ;  they  alone  succeed  also  in 
reproduction.  The  favourable  variations,  furthermore, 
are  transmitted.  Through  some  of  the  offspring  of 
these  already  better  adapted  individuals  there  occurs, 
again  absolutely  by  chance,  an  increase  of  the  favouring 
peculiarities ;  and  so  it  continues. 

It  is  seen  (a)  that  the  first  original  and  each  separate 
increase  of  a  favourable  change  as  regards  struggle 
for  existence  happens  by  pure  chance  ;  there  occur  also 
at  least  as  many  unfavourable  ones  ;  (b)  the  favoured 
individuals  become  preserved  because  they  alone  survive 
and  reproduce  themselves  ;  (c)  the  characters  which 


PKINCIPAL  ATTEMPTS  AT  EXPLANATION       159 

have  once  shown  themselves  as  favourable  are  inherited 
and  need  therefore  only  to  be  enhanced. 

It  therefore  appears  as  if  the  living  organisms 
adapted  themselves  purposefully  by  their  own  initiative. 
That,  according  to  Darwin,  is  a  deception. 

Of  adaptation  striven  for  nothing  is  said.  Among 
the  individuals  varying  without  object  or  plan  there 
must  however  be,  so  he  says,  still  some  at  least 
which  by  chance  indicate  an  improvement.  The  entire 
apparent  selection  only  requires  that  not  all  variations 
shall  be  favourable,  but  only  some,  which  are  then 
preserved. 

Of  a  plan  in  the  evolution  of  organisms,  of  a 
Creator  who  in  some  manner  established  this  plan  in 
the  organisms,  nothing  can  consequently  be  said. 

(ii)  Criticism. — l  (a)  Darwinism,  regarded  as  a  general 
hypothesis  of  evolution,  explains  absolutely  nothing 
regarding  what  the  organisms  actually  possess,  but  only 
why  they  have  not  certain  characters.  '  To  maintain 
that  certain  organic  qualities  can  be  explained  by 
natural  selection  is  indeed,  to  use  the  words  of  Naegeli, 

1  We  treat  here  of  Darwinism  as  it  has  finally  shaped  itself.  Darwin 
himself  was  clever  enough  not  to  express  all  consequences.  He  also  did 
not  exclude  the  influence  of  environment.  Nowhere  did  he  express  himself 
clearly  regarding  the  origin  of  life,  and  even  the  name  of  the  Creator  appears 
in  his  works.  But  all,  even  the  most  absurd  consequences,  lie  established 
in  the  system,  and  the  most  impossible  of  all — namely,  the  descent  of  man 
from  a  primitive  primary  form,  by  natural  selection  alone — he  has  finally 
(1871)  himself  deduced  and  had  the  sad  courage  to  publicly  advocate. 
Darwin  thereby  has  united  his  fate  with  that  of  his  theory  and  with  it 
become  bankrupt.  Darwin's  doctrine  has  often  been  criticized,  beginning 
with  the  noble  Wigand,  K.  E.  v.  Baer,  E.  v.  Hartmann,  up  to  our  own  time. 
See  Wagner,  Geschichte  des  Lamarckismus,  chap.  iii.  ;  H.  Driesch,  Philo- 
sophic des  Organischen,  I,  Leipzig,  1909,  .p.  260. 


160  THE  THEORY  OF  EVOLUTION 

precisely  as  if  one,  to  the  question,  "  Why  has  this  tree 
these  leaves  ?  "  should  reply,  "  Because  the  gardener  has 
not  cut  them  off."  That  would  naturally  explain  why 
the  tree  did  not  possess  more  leaves  than  are  actually 
on  it,  but  it  would  never  explain  the  presence  and 
origin  of  the  existing  foliage,  nor  do  we  understand  in 
the  least  why  the  bears  in  the  polar  regions  are  white 
if  we  are  told  that  bears  otherwise  coloured  could 
not  survive/  l 

(b)  Each  organism  is  an  harmonious  whole,  in 
which  the  most  varied  parts  are  combined  into  a  true 
unit.  It  is  unimaginable  that  a  symmetrically  and 
harmoniously  built  complex  organism,  in  which  one 
part  is  incapable  of  existing  without  the  others,  could 
build  itself  unless  in  the  hypothetical  commencing 
form  all  later  organs  and  parts  commenced  to  form 
simultaneously,  and  simultaneously  and  always  per- 
fected themselves  in  the  most  complete  harmony  with 
each  other.  That,  however,  Darwinism  will  not  and 
cannot  concede. 

If  it  be  also  considered  that  this  developing  organism 
at  each  stage — not  only  now — must  have  been  perfectly 
adapted  to  the  conditions,  because  otherwise  it  could 
not  have  lived,  it  is  clearly  seen  that  it  can  only  be  a 
matter  of  accidental  variations  of  some  already  perfectly 
developed  organs. 

Thus,  in  brief,  without  a  planned  total  development 
no  organism  could  construct  itself  from  simpler  forms  ; 
all  organisms  at  all  times  were  just  as  exactly  suited  to 

1  H.  Driesch  :    Philos.  d.  Organischen,  I,  p.  263. 


PKINCIPAL  ATTEMPTS  AT  EXPLANATION       161 

their  environments  as  those  of  to-day,  otherwise  they 
could  not  have  lived  ;  the  changes  in  them  which  have 
been  observed  are  transformations  within  their  type, 
which  type,  as  palaeontological  and  present  observa- 
tions show,  they  thoroughly  retain. 

(c)  Also  these  accidental  changes,  which  do  not  go 
beyond  the  particular  organic  type,  cannot  be  explained 
by  natural  selection.     If,  for  instance,  we  accept  that 
some   individual   snakes   become    venomous  ones,  the 
formation  of  a  poison  apparatus  is  necessary — a  hollow 
or  grooved  lengthened   tooth,  a  poison  gland,  and  a 
connection  between  the  poison  gland  and  the  tooth. 

This  apparatus  would  obviously  only  become  really 
of  service  to  the  venomous  individuals  concerned, 
when  for  the  first  time  it  acted  as  such  functionally; 
previously,  however,  it  would  rather  be  detrimental. 
How  came  it  then — on  the  assumption  that  the  poison 
apparatus  was  really  gradually  developed — that  tooth, 
gland,  and  canal  became  harmoniously  formed  without 
actual  utility  ?  That  evidently  happened  without  the 
aid  of  natural  selection — rather,  indeed,  against  it :  that 
was  effected  by  the  organism  itself  by  virtue  of  an 
innate  principle  of  purposeful  striving. 

Natural  selection,  therefore,  explains  no  single  positive 
acquisition  which  is  in  any  way  complexly  formed.1 

(d)  The  '  survival  of  the  fittest/  which  Darwin  accepts 
as  the  principle  of  higher  development,  is  not  proved. 

1  Compare  the  example  which  Driesch  (Philos.  d.  Organischen,  I,  p.  269) 
carried  out  thoroughly  on  Darwinian  lines,  viz.  the  acquisition  of  the 
regenerative  faculty  in  Lizards. 

M 


162 


THE  THEORY  OF  EVOLUTION 


If  a  whale,  for  instance,  opens  its  enormous  jaws 
and  swallows  thousands  of  small  crabs,  small  fish,  algae, 
etc.,  are  then  the  '  fittest '  in  any  way  spared  ?  If 
a  pig  seeks  acorns,  are  the  (  fittest '  spared  ?  etc.,  etc. 

(e)  Darwinism  has  not  withstood  the  proof  of  palceon- 
tology. 

The  classes  and  families  are  at  least,  as  wholes, 
found  thereby  to  be  precisely  so  separated  and,  in 
conjunction,  forming  systems  as  they  do  to-day.  The 
mixture  of  adapted  and  less  adapted  forms  has  not 
been  found  to  exist.1  The  changes  by  convergence  and 
specialization  cannot  be  comprehended  by  the  mere 
accumulation  of  the  most  minute  changes  without 
plan  and  guidance.2 

[The  words  {  specialization  ' — i.e.  change  in  a  deter- 
minate direction — and  '  convergence  '  likewise  imply 
this.] 

We  refrain  from  further  refutation — owing  to  the 
impossibility  that  definite  characters,  arising  by  pure 
chance,  could  long  maintain  themselves  against  the 
free  crossing  in  nature — of  the  denial  of  an  intervention 
of  the  Creator  both  in  connection  with  the  origin  of 

1  On  the  Darwinian  basis  it  is  entirely  incomprehensible  that  such  a 
thing  as  a  system  of  organisms,  constructed  of  complex  and  less  complex 
constituents,  can   exist !      According   to  the   Darwinian  doctrine   there 
could  only  be  amoebae  :  and  yet  the  system  is  not  yet  chaotic — as  it  must 
be  at  least  if  the  chance  theory  be  accepted — but  is  really  a  '  system  ' 
(H.  Driesch,  Philosophic  des  Organischen,  I,  p.  268). 

2  Deperet-Wegner :    Die  Umbildung  der  Tierwelt,  p.  38.     '  Do  I  go 
too  far  if  I  conclude  therefrom  [i.e.  from  the  discussion  on   Darwinism] 
that,  at  least  palseontologically,  the  question  of  the  origin  of  species  in 
their   full    extension    remains    unsolved  ? '     See    also    Steinmann :     Die 
geologischen   Grundlagen  der  Abstammungslehre,  Preface. 


PKINCIPAL  ATTEMPTS  AT  EXPLANATION       163 

life  and  the  plan  of  evolution  and  determination  of  its 
limits,  etc. 

(2)  Neo- Darwinism. 

(i)  Doctrine. — As  chief  advocate  in  this  direction 
ranks  Prof.  Weismann  (Freiburg  i/B.).  According  to 
him,  natural  selection  acts  not  on  the  complete,  fully- 
grown  organisms  themselves,  but  on  the  ( determinants ' 
—i.e.  on  the  hypothetically  smallest  material  parts  in 
the  nuclear  cells.  Each  quality  of  the  organism  has, 
according  to  him,  a  determining  part  in  the  sexual  cells. 
The  determining  parts  (=  determinants)  show  that 
variability  and  that  divergence  which  Darwin  imputed 
to  the  organism  itself.  Those  best  nourished  prevail 
over  the  weaker.  They  evince,  however,  that  influence 
in  the  grown  organism  only  if  the  change  in  the  deter- 
minants concerned  has  reached  a  sufficient  grade,  so 
that  they  then,  in  the  organism,  immediately  produce 
a  perfected  new  organ  as  the  first  expression  of  their 
influence,  since  it  is  only  when  the  organism  has  the  new 
organ  in  a  complete  form  that  natural  selection  sets  in. 

(ii)  Criticism. — The  determinants  are  hypothetical 
creations ;  if,  however,  they  exist  they  must  also  develop 
according  to  plan  and  harmoniously  and  always  in  the 
same  direction,  in  order  (for  example)  to  found  a  poison 
apparatus,  just  as  must  be  the  case  in  a  grown  organism. 

By  '  Weismannism/  therefore,  nothing  is  gained, 
and  the  whole  question  is  referred  to  the  microscopic 
stage,  from  which  we  learn  no  more  than  from  the 
matured  organism. 

M  2 


CHAPTER  II. 

SUGGESTIONS  FOR  RELIABLE  HYPOTHESES  OF 
EVOLUTION. 

THE  main  point  which  prevented  investigators,  like 
Cuvier  and  his  disciples,  from  accepting  a  genetic 
connection  between  the  present  and  previous  animal 
and  plant  forms  of  different  appearance,  was  the  con- 
viction that  the  organisms  always  retained  their  specific 
peculiarities.  It  could  not  be  conceived  that  the  earlier 
living  beings  had  so  greatly  changed  that  they  could  often 
only  be  allocated  to  the  same  family  or  even  sub-order, 
in  a  few  cases  even  to  the  same  genus,  but  only  quite 
exceptionally  to  the  same  species  as  the  present  ones. 
The  constancy  of  the  systematic  species  of  the  present 
is,  however,  not  established ;  rather  are  there  facts  which 
directly  indicate  a  capacity  of  variation  or  can  be  satis- 
factorily explained  only  by  acceptance  of  such. 

§  1.  Direct  observation  and  the  facts  of  animal  and 
plant  geography. 

(1)  Direct  observation  and  experiment. 

Breeding  experiments  show,  in  the  first  place,  that 
under  purposeful  supervision  of  the  reproduction  very 
varied  forms  can  arise,  which  often  remain  constant — as, 
for  instance,  dogs,  cattle,  pigeons,  and  the  remarkable 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES    165 

forms  of  the  cabbage.  As  in  '  evolution/  these  altera- 
tions can  certainly  hardly  be  directly  considered,  but 
they  show  that  the  organism  is  no  stubborn  unchange- 
able form. 

Observations  were  made  and  experiments  confirmed 
that  the  external  conditions  of  existence — such  as 
climate,  particularly  the  temperature,  and  nutrition — 
could  induce  such  transformations  and  fix  them  per- 
manently in  the  organism,  as  would  suffice  to  form 
various  '  species/  even  if  the  origin  of  the  changed 
forms  had  not  been  known.1 

Thus  there  resulted  from  seeds  of  one  and  the  same 
mother  plant,  which  were  sown  partly  at  high  elevations 
and  partly  at  lower  and  partly  in  the  valley,  plants 
of  fundamentally  different  external  appearances.  The 
alpine  forms  were  more  congested,  hairier — as  protec- 
tion from  cold — the  leaves  smaller  and  darker  green,  the 
flowers  fewer  and  more  intensely  coloured,  than  those 
of  the  valley.  Were  the  alpine  forms  subjected  for 
a  long  period  to  the  same  conditions,  these  changes 
could  become  permanent,  but  the  tendency  is  im- 
mediately shown  to  retain  the  new  characters  even  if 
their  seed  be  sown  again  in  the  valley.3 

In  Angora  not  only  the  goats,  but  also  cats  and 
dogs  have  fleecy  wool.  Pure-bred  dogs  cannot  be 

1  See,  particularly  as  regards  the  following  remarks,  R.  Heffe  :  Abstain- 
mungslehre  und  Darwinismus,  Leipzig,  1904,  p.  96. 

2  The  author  could  convince  himself  of  this  in  Innsbruck,  where,  in 
the  Botanical  Garden,  mountain  and  valley  forms  were  shown  as  progeny 
of  one  and  the  same  mother  plant  (Brassica).     From  their  appearance 
no  one  would  have  presumed  so  close  a  relationship. 


166 


THE  THEORY  OF  EVOLUTION 


maintained  continuously  in  India  :  they  become  smaller, 
slenderer  and  with  more  pointed  features ;  an  exception 
is  the  spaniel,  which  can  be  kept  thoroughbred  for  a 
long  time  by  breeding.  '  The  Hares/  says  Ch.  Deperet,1 
'  in  the  level  regions  of  North  and  Central  France  always 
differ  from  those  of  Provence  in  the  South  by  being  of 
larger  dimensions,  having  longer  and  thicker  hair, 
long  and  thickly  haired  ears,  and  a  darker  fur.  These 
differences  become  more  emphasized  as  we  proceed 
from  Provence  towards  Africa.  The  Algerian  Hares 
are  scarcely  more  than  half  as  large  as  European  ones, 
while  when  the  Sahara  region  is  reached  the  Hares  are 
very  small  and  of  an  "  Isabelline  "  colour.  .  .  .  Similar 
specific  differences  occur  in  the  Foxes  and  Weasels  of 
the  North  and  South  of  Europe/ 

The  composition  of  the  soil  is  of  great  importance 
for  the  development  of  plants  and  more  or  less  for 
all  plants  in  the  same  direction,  hence  we  speak  of  the 
desert,  salt,  and  limestone  flora.  The  shells  of  snails 
are  certainly  influenced  by  the  composition  of  the  soil : 
on  soils  rich  in  lime  they  are  thick  and  wrinkled,  on 
silicious  ones  thin  and  smooth. 

Ordinary  garden  cress,  frequently  watered  with 
salt  water,  acquires  fleshy  leaves,  like  many  plants 
which  grow  on  the  seashore. 

Instructive  are  the  experiments  which  have  been 
made  with  regard  to  the  influence  of  temperature. 
Our  Woodnettle  Moth  (Vanessa  levana),  for  instance, 
has  two  forms,  spring  and  summer.  If  the  chrysalis 

1  Umbildung  der  Tierwelt,  p.  116. 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES    167 

of  the  spring  form,  which,  normally  hibernates  and  is 
therefore  exposed  to  cold,  be  induced  to  develop  by 
artificial  warmth,  the  summer  form  emerges,  while 
the  chrysalis  of  the  summer  form,  exposed  to  artificial 
cold,  yields  the  spring  form.  Thus  the  difference 
between  the  Vanessa  levana  forms,  which  is  rather 
striking,  would  presumably  originate  through  the 
influence  of  warmth. 

Even  the  method  of  reproduction,  as  for  example 
with  fungi,  can  be  influenced  by  change  of  temperature. 

Another  example  is  afforded  by  the  Fireflies  :  these, 
both  in  Germany  and  the  Riviera,  show  two  different 
varieties  which,  as  experiment  has  proved,  are  due  to 
warm  influence.  Since  warmth  generally  accelerates 
maturity,  so  we  find,  in  snails,  that  the  shell  shows  one 
or  more  turns  less  under  warm  conditions,  while  cold 
and  a  very  favourable  environment  can  defer  maturity 
and  thus  give  the  animals  time  to  add  under  some 
circumstances  one  or  more  spiral  turns  to  the  normal 
number.1 

Nutrition  has  also  influence  on  the  formation  of 
animals,  independently  of  the  directly  detrimental 
want  of  such.  Thus  the  colour  of  many  birds  may 
be  altered  by  the  kind  of  food  given. 

The  collective  terms,  indeed,  such  as  midland, 
or  northern  flora  and  fauna,  etc.,  which  indicate  to 
the  botanist  or  zoologist  a  quite  definite  and  objectively 

1  Deperet-Wegner :  Die  Umbildung  der  Tierwelt,  p.  123.  That  is 
very  important  for  the  judgment  of  palseontological  finds,  in  which  the 
whole  transformation  is  sufficiently  often  confined  to  the  enhancement 
of  such  deviations. 


168  THE  THEOKY  OF  EVOLUTION 

determined  habitat  or  such  peculiarities  as  only 
there  present  themselves,  show  that  the  influence 
of  climate,  temperature,  and  soil  constitution,  affects 
the  construction  and  nature  of  organisms,  and,  as 
experiment  shows,  can  also  alter  the  form. 

Supplementary  Note. — Nature  of  the  variations. 

Darwin,  as  is  known,  accepted  variations  which 
were  not  in  any  particular  direction  and  of  a  minimal 
character,  among  which  natural  selection  should 
act.  More  recently  there  have  been  made  observa- 
tions and  experiments  which  show  that  in  many 
individuals  considerable  variations  can  suddenly 
appear,  the  constitution  of  which  can  be  to  some 
extent  estimated  beforehand. 

Thus  H.  de  Vries  l  observed  that  with  the  Evening 
Primrose  (Oenothera  Lamarkiana)  within  a  short  period 
seven  new  species  arose.  Such  sudden  deviations 
from  the  parental  type,  apparently  without  any 
external  reason  and  which  remain  constant,  he 
termed  '  mutations/ 

Mendel's  3  experiments  have  shown  that  by  crossing 
two  races  of  plants  differing  in  one  or  several  characters 

1  Die  Mutationstheorie,  I,  Leipzig,  1901,  p.  151. 

2  Upon  the  experiments  of  Abbe  Gr.  Mendel  (published  1865  and  1869, 
but  then  forgotten  and  again  '  discovered  '  in  1900,  simultaneously  by 
Correns,  de  Vries  and  Tschermak)   there  is  based  an  entire  literature. 
Mendel's  work  has  newly  appeared  in  Ostwald's  Klassikern  der  exacten 
Wissenschaften,  No.   121,    Leipzig,   1901.      See  Bateson's    The  Methods 
and  Scope  of   Genetics,    Cambridge,  1908 ;    and    Mendel's    Principles   of 
Heredity,  Cambridge,  1909  ;  W.  Johannsen's  Elemente  der  exacten  Erblich- 
keitslehre,  Jena,  1909  ;  C.  Correns,  Uber  Vererbungs  Gesetze,  Berlin,  1905  ; 
J.  P.  Lotsy,  Vorlesungen  iiber  Descendenztheorien,  I,  Leipzig,  1906,  p.  99. 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES    169 

(Peas,  for  instance,  with  different  flowers  or  colour  of 
seed),  new  combinations  can  be  formed  according  to 
mathematical  laws,  which,  when  care  is  taken  to  ensure 
self-fertilization,  are  constant.  The  experiments  render 
it  probable  that  accidental  qualities,  such  as  size, 
colour,  length  of  life,  and  many  others,  are  connected 
with  certain  corporeal  parts  (Gens)  and  maintain 
an  independence  in  the  organism.  If,  for  instance, 
there  be  crossed  a  dwarf  race  with  a  very  large  one, 
it  may  happen  that  all  the  progeny  may  be  large  or 
all  dwarf,  according  to  whether  the  '  gen  '  of  the  c  large  ' 
or  that  of  the  '  dwarf '  becomes  utilized. 

Mutations  and  Mendelism  both  are  adverse  to  the 
smallest  scarcely  appreciable  deviations.  The  greatest 
hopes  have  been  built  upon  Mendelism,  which,  however, 
have  mostly  been  unjustified.  Crossing  occurs  certainly 
in  free  nature  generally  only  between  individuals  of 
the  same  species.  Most  of  the  systematic  species  do 
not  admit  of  fruitful  intercrossing.  Lepus  limidus 
(the  Hare)  never  crosses  with  the  northern  Lepus 
variabilis  ;  the  two  species  of  Sparrows,  house  and  field 
sparrow,  never  cross  ;  horse  and  ass  as  a  rule  only  by  use 
of  artifice,  etc.  Just  so  there  has  hitherto  been  no  cross 
between  apple  and  pear,  despite  their  near  relationship. 

With  plants  it  is  a  general  rule  that  self-fertiliza- 
tion should  be  avoided  (lowest  limit),  but,  almost  equally 
so,  crossing  between  species  (highest  limit).1  Some 

1  '  The  union  of  sexual  cells  follows,  as  a  rule,  only  if  they  are  derived 
from  individuals  of  the  same  species  '  (Strasburger :  Lehrbuch,  p.  264). 
'  Self-fertilization  '  is  mostly  only  an  '  aid  in  need  '  (same  author). 


170  THE  THEORY  OF  EVOLUTION 

exceptions,  however,  are  certainly  known  (Quince  and 
Apple).  Hence,  by  crossing,  it  is  only  a  question  of 
new  combinations  of  specific  characters  which  are  of 
quite  subordinate  nature,  such  as  colour  and  size.  In 
order  that  the  new  forms  should  remain  constant 
strict  in-breeding  is  necessary,  which,  in  most  cases, 
can  only  be  artificially  ensured.  Consider  only  Mendel's 
experiments.  That  by  crossing  the  '  analytical  formula 
of  an  organism  '  may  be  ever  discovered  is  a  dream. 

Some  palseontological  series  and  many  observations 
of  the  present  organisms  permit  of  recognition  that 
even  quite  gradual  transitions  lead  from  one  to  another 
species,  especially  the  evidence  of  convergence  and 
'  specialization/1 

All  these  observations  tell  us  obviously  only  how, 
by  suddenly  appearing  mutations,  by  crossing  and  by 
gradual  change  in  determined  directions  (caused  indeed 
by  gradually  changing  environment),  new  forms  appear 
within  the  limits  of  definite  organic  types. 

(2)  Suggestions  derived  from  animal  and  plant  geo- 
graphy concerning  the  origin  of  transformations." 

It  is  not  all  deviations  which  appear  in  the  progeny 
of  the  same  animal  or  plant  parents  which  can  be 
imputed  to  the  influence  of  changed  environment. 

1  Deperet-Wegner :    Die  Umbildung  der  Tierwelt,  p.  138. 

2  See  J.  P.  Lotsy,    Vorlesungen  iiber  Descendenztheorien,  II,  p.  483  ; 
R.  Heffe,    Abstammungslehre   und   Darwinismus,    p.   44  ;    A.  Wei  smarm  : 
Vortrdge  iiber   Descendenztheorie,  II,  p.  235  ;    Einfluss  der  Isolierung  auf 
die  Arfbildung ;    L.  Plate,  Selectionsprinzip  und  Probleme  der  Arfbildung, 
Leipzig,  1908,  p.  396. 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES    17i 

There  are  plants  and  animals  which,  precisely  in  the 
same  habitat,  or  in  the  same  region,  often  produce 
spontaneous  deviations — i.e.  without  a  recognizable 
external  cause.  Such  £  bad  '  species  from  the  beginning 
constituted  the  cross  of  the  systematist  who  desired 
to  give  a  name  to  each  form  and  thus  '  pulverized/ 
as  Deperet  puts  it,  the  animal  species  concerned, 
so  that  eventually  nearly  every  individual  bore  a 
special  name.  Among  the  plants  there  belongs  to  this 
category  the  Evening  Primrose  (GEnothera  Lamarckiana), 
the  Blackberry,  the  Hawkweed,  and  others  ;  among 
the  animals  the  Vine  Snail  (Helix  striata),  and  some 
Mussels  (particularly  Unio),  are  the  most  notoriously 
'  bad '  species. 

These  transformations,  however,  do  not  go  so  far 
that  the  connection  with  a  common  '  basal  form  ' 
cannot  at  once  be  recognized.  More  extended  and  more 
constant  transformations  established  in  organisms 
arise,  however,  when  an  animal  or  plant  form  occurs 
in  a  definite,  well-separated  (isolated)  region  with 
peculiar  environment.  Then  the  so-called  local  races 
and  local  species  are  formed,  which,  by  the  exclusion 
of  free  crossing  with  new  blood  and  through  long- 
continued  isolation,  assume  forms  which  can  then  only 
be  classed  in  the  same  genus,  sometimes  indeed  only 
in  the  same  family,  as  their  original  ancestors. 

We  will  now  treat  more  in  detail  those  facts  from 
animal  and  plant  geography  of  the  present  organisms 
in  connection  with  which  the  influence  of  the  strictest 
separation,  and  the  in-breeding  connected  therewith 


172  THE  THEORY  OF  EVOLUTION 

which  has  been  effective  through  long  periods,  has 
made  itself  felt. 

The  conclusions  thereby  arrived  at  form  one  of 
the  main  supports  of  the  transformation  hypothesis 
and  the  best  refutation  of  the  absolute  fixity  of  species 
which  was  formerly  accepted. 

The  most  favourable  conditions  are  presented  in 
the  first  place  by  the  small  oceanic  islands  which  owe 
their  existence  to  submarine  volcanic  outbreaks.  We 
will  first  give  a  few  examples  in  detail ;  subsequently 
we  will  collect  the  points  of  evidence  which  speak 
for  transformation  as  actually  established. 

1.  The  Azores  and  Bermuda  Islands  (both  of  vol- 

canic origin). 

Azores  (1400  Km.  from  Portugal)  : 

69  Snail  species,  32  '  indigenous'  )  the  rest 
53  Bird  species,  1  „  j  European. 

Bermuda  (about  1400  Km.  from  America)  : 
Many  Snails — one-fourth  indigenous,  the  others 
American. 

2.  St.  Helena  (1800  Km.  from  Africa,    3000   Km. 

from  S.  America)  : 

Land  Vertebrates  entirely  absent. 

Land  Birds — 1  species  (Regenpfeifer)  indigenous. 

Land  Snails — 20  species,  all  indigenous,  with- 
out nearer  relationship. 

Beetles — 129  species  (128  indigenous) ;  they  are 
divided  into  25  genera,  all  indigenous ;  two- 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES    173 

thirds  of  them  are  Weevils  whose  larvae  live 
in  wood  (driftwood). 

3.  Hawaii  (volcanic ;   400  Km.  distant  from  land) : 

Land  Vertebrates — 2  Lizards,  indigenous ;  one 
of  these  forms  a  genus  in  itself. 

Land  Birds — 16  species,  indigenous ;  they  are 
divided  into  10  genera  of  which  5  again  form 
an  indigenous  family. 

Snails :  Achatinella,  20  species,  only  occurs  here. 

Islands  of  the  most  recent  origin  show,  as  yet,  as  we 
might  expect,  no  peculiarities  :  for  instance  Krakatoa, 
near  Java  (risen  in  1883).  The  20  plant  species  (1904) 
belong  to  16  families,  just  as  chance  brought  them 
together. 

These  examples  show  in  the  first  place  that  these 
islands  became  populated  from  the  nearest  continent, 
since  they  are,  as  can  be  proved,  of  volcanic  origin, 
and  therefore  possessed  no  £  creation '  of  their  own 
from  the  beginning.  There  are,  furthermore,  found 
quite  predominantly  only  such  animals  as  can  be  most 
easily  imported — such  as  snails,  whose  eggs  or  larvae 
abound  in  mud — by  Waterfowl,  and  Beetles  (Weevils)— 
whose  larvae  live  in  wood — by  driftwood  ;  in  addition 
naturally  birds,  which  also  show  the  least  indigenous 
forms  because  they  are  not  confined  to  the  islands 
and  can  cross  more  freely. 

For  the  doctrine  of  descent  from  the  observations 
given  it  may  be  concluded  that  animals,  which  are  con- 
fined to  a  narrowly  restricted  region  where  somewhat 


174  THE  THEORY  OF  EVOLUTION 

differing  vital  conditions  prevail,  deviate  from  their 
original  specific  and  generic  characters  through  so- 
called  adaptation  to  the  changed  environment. 
That  these  deviations  are  most  easily  determined  in 
a  definite  direction  on  such  small  islands  arises 
obviously  from  the  necessity  of  close  in-breeding 
between  the  few  individuals  which  chance  has  brought 
together. 

It  can  furthermore  be  established  that  likewise 
entire  continents,  which  have  been  isolated  since  very 
long  periods  (Australia),  or  only  in  the  younger  geological 
periods,  were  again  connected  with  others  (like  South 
and  North  America  in  the  Tertiary  era),  possess  quite 
peculiar  animal  worlds  (like  Australia  and  South  America 
proper)  and  only  on  the  frontier  regions  show  a  mixture 
(for  instance,  the  extreme  North  of  South  America  and 
Central  America). 

For  Australia  the  position  is  considered  to  be  ap- 
proximately this  :  Australia  became  separated  when  the 
most  primitive  forms  of  the  Mammalia  first  appeared— 
i.e.  the  Cloaca1  and  marsupial-like  forms — or,  what  is 
much  more  probable,  this  continent  possessed  at  the 
time  of  its  isolation  only  Marsupials  and  Cloaca  animals 
and  received  also  no  other  orders  of  Mammalia,  or  again 
(in  the  style  of  the  popular  doctrine  of  evolution),  no 

1  Cloaca  signifies  in  zoology  the  common  region  into  which  both  the 
urogenital  system  and  the  digestive  canal  open  ;  all  other  orders  have 
for  both  systems  separate  external  openings  :  '  cloaca  '  therefore  signifies 
a  trifling  degree  of  differentiation  which  served  and  serves  as  the  best 
criterion  for  the  determination  of  different  grades  of  perfection.  The 
ant-eater  (Echidna)  and  the  Ornithorhynchus  belong  to  this  group. 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES    175 

higher  types  were  developed  from  the  lower.1  A  fact 
it  is  that  with  the  exception  of  forms  introduced  by 
man  and  of  such  species  as,  like  mice,  bats,  and  seals, 
can  easily  make  their  way  from  island  to  island,3  no 
other  mammalian  orders  were  found  in  Australia.  What 
is  remarkable,  however,  in  this  connection  is  the  circum- 
stance that  the  Marsupials  assume  the  most  varied  modes 
of  existence  and  suitable  construction  of  the  body  : 
there  are  flying  marsupials,  which  resemble  the  flying 
squirrel ;  root  and  plant-eaters — i.e.  the  Wombat 
(similar  to  the  Marmot)  ;  insect-eaters  with  the  jaw 
of  the  Sorex  ( ?  Shrewmouse)  or  Hedgehog  ;  Carnivora — 
for  instance  the  marsupial  Marten  with  the  typical 
equipment  of  the  order  of  Carnivora  ;  springers — e.g.  the 
Kangaroo  (like  the  Steppe  mice). 

All  are  Marsupials  in  other  respects,  however,  con- 
structed precisely  like  the  representatives  of  the  other 
mammalian  order,  whose  mode  of  existence  they  pursue. 

The  significance  of  these  facts  appears  close  at  hand. 
The  present  forms,  which  obviously,  as  regards  every- 
thing connected  with  a  quite  special  mode  of  existence, 
are  constituted  to  one  end  (einseitig),  do  not  give  the 
impression  of  original  animals,  since  these,  according 

1  That  the  Allotheria  of  the  Trias — which  are  considered  as  being  the 
first  Mammals — are  the  ancestors  of  the  higher  orders,  is  in  the  meantime 
a  simple  assumption.     They  are  also   '  unfortunately  very  imperfectly 
known '    (R.  Hertwig  :    Lehrbuch,  p.  590).     According  to  Deperet  the 
remains  cannot  well  be  otherwise  considered. 

2  R.  Hertwig  :  Lehrbuch,  p.  591.     The  Marsupials  are  confined,  except 
the    South  American   Kangaroo    Rats,    to    Australia;    earlier — in    the 
Secondary  and  Tertiary  periods — they  existed  in  Europe  and  North  and 
South  America, 


176  THE  THEOEY  OF  EVOLUTION 

to  the  evidence  of  palaeontology  in  each  group,  are 
not  yet  so  specially  constituted,  but  show  in  jaw  and 
other  equipment  a  more  general  character.  It  is  this 
circumstance  precisely  which  enables  them  to  nourish 
themselves  in  various  ways  and  to  live  in  various  regions 
and  habitats.  Marked  specialization — for  instance  in 
the  jaw  and  organs  of  locomotion  or  with  respect  to 
the  habitat — will  consequently  be  best  considered  as 
really  subsequently  acquired  '  adaptive '  characters. 

In  Australia — which,  as  a  continent,  in  contrast 
with  the  small  marine  islets,  presented  opportunities 
for  the  most  diverse  modes  of  existence — the  Marsupials 
have,  therefore,  it  is  concluded,  assumed  the  most  diverse 
forms  to  fit  them.  Since,  however,  they  remained 
Marsupials,  therefore  this  example  shows  that  they 
present  a  real  type  which  only  varies  but  is  not  aban- 
doned. If  therefore — which  cannot  be  exactly  proved— 
the  present  forms  of  the  Australian  Marsupials  have 
really  developed  themselves  by  differentiation,  then 
they  form  at  the  same  time  a  fine  proof  that  certain 
basal  forms  are  firmly  retained.  Time  and  opportu- 
nity for  the  full  development  of  their  entire  evolutional 
capacity  the  Marsupials  have  certainly  had,  but  other 
orders  they  have  not  produced.  The  same  thing  we 
must  assume  also  for  Europe  and  America  if  we  will  be 
logical,  although  the  pakeontological  evidence  in  favour 
of  a  genetic  connection  of  definite  mammalian  groups 
with  each  other  is  lacking. 

On  other  continents — like  North  America  and  Asia, 
together  with  Northern  Europe,  which  for  a  very  long 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES     177 

time  were  connected  across  the  Behring  Straits — the 
animal  world  is  very  similar,  since  fresh  blood  was 
constantly  coming  in  which  by  continued  crossing 
rendered  an  alteration  in  a  definite  direction  impossible. 
The  objection  might  yet  be  raised  that  the  various 
continents  could  certainly  have  had  their  own  fauna 
and  flora  from  the  beginning.  But  then  it  is  entirely 
forgotten  that  the  present  continents  did  not  always 
exist :  how  otherwise  could  marine  animals  be  found 
in  the  alpine  strata  ?  Furthermore  it  is  certain  that 
in  many  geological  epochs  the  animal  and  plant  worlds 
in  Europe  and  America  were  almost  entirely  the  same— 
for  instance,  in  the  coal  period ;  that  at  times,  over  the 
entire  northern  hemisphere  as  far  as  Greenland,  a  warm 
climate  prevailed — in  our  regions  a  tropical  one,  without 
marked  seasons ;  and  that  even  in  the  Ice  Age  with  us 
the  Siberian  plants  and  those  of  the  high  Alps  still 
lived  in  the  valleys.  There  is  thus  proved  by  evidence 
that  there  has  been  a  continuous  changing  and  constant 
wandering  from  place  to  place  :  therefore  one  cannot 
speak  of  the  countries  which  at  present  chance  to  project 
above  the  level  of  the  sea  as  having  their  own  organisms 
from  the  beginning. 

§  2.  Suggestive  points  in  the  domain  of  Parasitism  and 

Symbiosis. 

A  very  fruitful  domain  for  historical  evolutionary 
hypotheses  is  presented  by  the  manifold  relations  of 
various  species  of  animals  and  plants  to  each  other  or 
of  animals  to  plants.  When  individuals  of  different 


178  THE  THEORY  OF  EVOLUTION 

species  enter  into  close  mutual  relations,  then  this  is 
based  either  on  utility  on  one  side  only  or  on  mutual 
support.  In  the  first  case  we  speak  of  Parasitism,  in 
the  second  of  Symbiosis. 

(1)  The  adaptive  phenomena  of  the  Parasites. 

We  will  confine  ourselves  here  to  the  true  Parasites, 
independently  of  the  more  or  less  legitimate  kinds  of  life 
association  which  do  not  imply  an  actual  dependence 
but  rather  a  companionship.1 

True  Parasites  are  organisms  which  exist  either 
upon  or  in  other  organisms  in  order  to  nourish  them- 
selves by  the  living  substance  or  already  prepared  nutri- 
tive sap  of  the  same.3  With  this  peculiar  mode  of  life 
on  or  in  other  living  beings  (termed  '  host  animals  '  or 
'  host  plants  ')  the  bodily  equipment  and  the  needs  of 
the  Parasites  are  in  the  most  perfect  accord.  The  pre- 
ponderant majority  of  the  Parasites  are  adapted  physio- 
logically and  morphologically  to  their  abnormally 
deviated  mode  of  existence  :  physiologically  by  the  fact 
that  they  necessarily  require  for  the  maintenance  of 
their  existence  the  nutrition  to  be  derived  from  a  definite 
species  of  animal  or  a  group  of  related  species  ;  morpho- 
logically in  so  far  as  their  bodily  construction  is  arranged 
for  the  acquisition  of  precisely  this  nourishment.3 

1  A  short   description  is  found  in  all  botanical  and  zoological  text- 
books.    Prof.  L.  v.  Graff  has  treated  of  Das  Schmarotzerthum  im  Tierreich 
in  his  work  Wissenschaft  und  Bildung,  No.  5,  and  given  an  excellent  sum- 
mary of  the  observations  made  in  that  connection.     With  his  interpretation 
of  the  facts  we  cannot,  however,  always  agree. 

2  Ibid.  p.  8. 

3  Ibid.  p.  9. 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES     179 

From  this  agreement  between  construction  and 
needs  on  the  one  side,  and  the  mode  of  existence 
on  the  other,  there  follows  nothing  in  support  of  any 
evolution  whatever,  since  adaptability  to  purpose— 
and  this  agreement  is  nothing  else — is  a  general 
phenomenon  throughout  the  whole  organic  world :  all 
animals  and  plants  possess  those  organs  and  capacities 
(i.e.  arrangements  in  plants)  required  to  fit  them  exactly 
for  existence  in  their  habitats  or  resorts,  and  to  enter 
into  or  be  brought  into  relations  with  those  objects  or 
organisms  which  are  necessary  for  the  maintenance  of 
life  and  of  reproduction. 

The  closer  observation  of  the  Parasites  affords, 
however,  several  very  important  points  in  support  of  the 
assumption  that  their  mode  of  existence,  and  conse- 
quently their  construction  and  their  physiological 
constitution  (as  means  to  an  end),  are  something 
subsequently  acquired  (secondary)  and  not  of  primary 
origin  ;  or,  expressed  in  the  language  of  the  time,  the 
present  form  of  the  Parasites  in  the  adult  stage,  and 
many  peculiarities  of  the  embryological  genesis,  present 
the  result  of  a  transforming  (evolutionary)  process— 
they  are  '  adaptations/  If  that  be  really  the  case 
then  certainly  the  transition  to  the  parasitical  mode  of 
life  has  been  the  cause  of  the  production  of  the  most 
manifold  forms  of  animals  and  plants,  which  often 
enough  we  can  only  bring  into  our  '  system  '  with 
great  difficulty. 

'  Adaptation  '  (Anpassung)  therefore  does  not  imply 
every  agreement  between  construction  and  function. 


180  THE  THEORY  OF  EVOLUTION 

The  meaning  of  the  word  expresses  this  :  to  c  self- 
adapt  '  (sich  anpasseri),  signifies,  indeed,  the  production 
of  an  agreement  by  changes  which  in  the  majority 
of  cases  commence  in  the  mode  of  life  and  react  upon 
the  construction.  Graff  expresses  this  in  the  words  : 
'  their  deviation  from  the  normal  mode  of  life/ 

H.  Driesch  has  expressed  himself  very  tellingly 
regarding  adaptation.1  '  True  '  or  secondary  adapta- 
tions, according  to  him,  only  occur  when  c  any  species 
of  variation  in  function  occurs  which  agrees  with  a 
variation  of  any  one  factor  of  the  medium/  '  We  call 
secondary  adaptations  all  occurrences  in  the  domain 
of  form  construction  and  function  which  serve  to 
restore  the  disturbed  condition  on  lines  which  lie  outside 
the  realm  of  so-called  normality/  3 

The  type  of  a  bird,  for  instance,  might  justly  be 
termed  an  adaptation  if  it  could  be  shown  what  animal 
produced  its  wings,  etc.,  by  adoption  of  an  aerial 
existence.  So  long  as  that  cannot  be  done,  the  bird, 
with  its  construction  and  its  modes  of  life,  is  a  given 
type  and  not  an  evolved  (geworden)  one.  Until,  how- 
ever, this,  the  only  correct  assumption,  be  everywhere 
and  logically  followed  up,  in  scientific  parlance,  a  long 
time  must  yet  elapse.  In  the  meantime  all  that  is  to 
the  purpose  is  '  adaptation/ 

As  bases  for  the  assumption  that  the  parasitical 
mode  of  life,  and  the  therewith  connected  bodily  con- 
struction of  the  Parasites  are  acquired,  we  may  state— 

1  Philosophie  des  Organischen,  I,  p.  185. 

2  Ibid.  p.  189. 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES     181 

(a)  From  the  outset  it  is  improbable  that  from  the 
beginning  there  were  organisms  which,  for  the  preserva- 
tion of  their  individual  life,  were  dependent  upon  the 
separate  vital  functions  of  others,  since  they  themselves 
lack  the  capacity  of  performing  them  alone. 

The  fungi  plants,  generally  speaking,  can  no  longer 
assimilate,  and  thus  cannot  fulfil  the  task  which  falls 
upon  the  plant  kingdom  taken  as  a  whole.  To  the 
existence  of  an  animal  there  appertains  free  locomotion 
and  the  formation  of  sense  organs ;  the  animal  Parasites, 
however,  often  dispense  entirely  with  both,  with  the 
exception  perhaps  of  feelers.1  Multicellular  animals 
have  also  their  special  functions — in  contrast  to  the 
unicellular — transferred  to  separated  tissues  (organs)  ; 
many  Parasites — which,  in  addition,  in  their  total 
habit  belong  to  the  Worms  or  the  Crabs,  i.e.  to  fairly 
differentiated  organisms — often  lack  even  an  intestinal 
system  of  their  own. 

(b)  Had   there    been   existent  from  the   beginning 
Parasites   of  the  present  form  and  mode  of  existence 
there  would  have  resulted,  at  least  in  some  cases,  very 
singular  consequences.    We  know  Parasites  which  must 
live  not  only  in  one  particular  species  of  animal,  but 
often  even  in  one  particular  organ.     The  worm  Oxyuris 
vermicularis   can  only   live  in  man — with  him  and  in 
him  must  it  also  have  been  created.     The   Trichinse 
can  only  maintain  life  in  cross-fibred  muscles.     A  larval 
form    (oncosphcera)    of  the    tapeworm  (tcenia  ccenurus) 
can  only  develop  itself  further  in  the  brain  and  spinal 

i  R.  Hertwig  :  Lehrbuch  der  Zoologie,  p.  155. 


182  THE  THEORY  OF  EVOLUTION 

cord  of  the  sheep.  The  malaria  Parasites  (some 
Plasmodium  species)  would  have  had,  in  that  case, 
from  the  beginning  the  positive  task  of  causing 
fever  and  death  to  man,1  since  only  to  that  end  are 
they  constructed.  Only  in  the  red  corpuscles  of  the 
blood  of  man  or  in  the  intestine  of  the  mosquitoes 
(some  Anopheles  species)  can  the  various  reproductive 
stages  be  carried  through. 

Have  there  been  from  the  commencement  beings 
whose  existence  is  necessarily  dependent  upon  a  constant 
exchange  of  relations  between  men  and  mosquitoes  ?  3 
If  the  man  be  not  there,  then  the  purely  vegetative 
increase  cannot  happen  and  therewith  the  first  condition 
for  further  development  falls  to  the  ground.  If  there 
be  no  mosquitoes  then  the  sexual  generation  cannot 
take  place,  and  the  play  is  at  an  end.  The  malaria 
Parasites  are  thus  physiologically  formed  for  this  mode 
of  life — i.e.  they  have  the  need  of  so  existing  and  the 
necessary  equipment  to  attain  their  object ;  therefore 
the  spores  introduced  into  the  blood  have  a  pointed 
form,  to  enable  them  to  bore  into  the  blood  corpuscles. 

(c)  Had  the  parasitical  mode  of  existence  been 
present  from  the  beginning,  particularly  to  its  present 
extent  and  in  its  extreme  development,  then  there 

1  According  to  investigation  so  far  the  Malaria  Plasmodes  occur  only 
in  man  and  as  a  phase  of  Schizogonia  (=  increase  by  formation  of  several 
individuals  from  one  by  fission). — F.  Doflein  :   Die  Protozoen  als  Parasiten 
und  Kranlcheitserreger,  Jena,  1901,  p.  145. 

2  Ibid.  p.  130.     We  have  to  do  with  Parasites  which,  '  in  the  exchange 
of  hosts  between  two  organisms,  live  in  man  and  a  member  of  the  Fly 
family '  ;   also,  p.   147 :    '  Another    mode   of   transfer  than  through   the 
mosquito  cannot  be  according  to  our  present  knowledge.' 


SUGGESTIONS  FOE  RELIABLE  HYPOTHESES     183 

would  have  been  also  from  the  beginning  those  shape- 
less forms  which  we  see  often  enough  in  Parasites. 
On  this  assumption,  however,  how  could  it  be  explained 
that  there  are  transitions  between  shapeless  Parasites 
and  normal  ones — i.e.  free-living  representatives  of  a 
defined  type  in  which  otherwise  the  separation  of  type 
appears  to  be  so  clear  ? 

The  Platodes,  for  instance,  have  their  tropical  repre- 
sentatives in  the  free-living  Planaria  (Turbellaria)  ;  they 
possess  an  intestine  and  numerous  cilia  as  organs  of 
locomotion  which  cover  the  whole  body  like  a  garment. 
There  is  also  known  a  large  group  of  similar  animals 
which  may  also  be  recognized  as  Platodes  and  are  called 
Trematodes.  They  are  thoroughly  parasitical  and 
provided  with  an  intestine,  but  without  cilia,  bearing 
suckers  and  hooks  which  serve  to  attach  them  in  or 
outside  their  hosts.1  In  many  forms  the  really  digesting 
portion  of  the  intestine  disappears  entirely ;  there 
remain  only  the  oesophagus  and  the  anus.  Again, 
other  similar  animals  are  the  Tapeworms,  all  parasites, 
without  intestine  or  cilia  ;  they  are  also  the  most 
extreme  parasites  of  the  whole  Worm  group.  One 
is  inclined  to  regard  the  three  classes  cited  as  represen- 
tatives of  one  and  the  same  animal  form  which,  in  the 
free-living  Turbellaria  (there  are  also  parasitical  ones), 
exhibit  the  unchanged  original  type,  since  there  are 
also  among  the  Turbellaria  the  one  or  the  other  extreme 
parasitical  kind,  which  shows  similar  retrogression  to 
that  of  the  worms  ranked  with  the  Tapeworms.  That 

1  Graff :    Wissenschajt  und  Bildung,  p.  25. 


184 


THE  THEOKY  OF  EVOLUTION 


there  are,  however,  true  Turbellaria  is  shown  by  their 
different  embryonic  development  from  that  of  the 
Tapeworms.  There  would  therefore  also  have  been 

in  the  Tapeworms  a  marked 
alteration  in  the  genesis  of 
the  embryo  ;  the  adult  forms 
of  a  Tapeworm  and  of  such 
parasitic  Turbellaria  would  by 
themselves  form  no  reason  for 
establishing  different  classes. 

As  between  Tapeworms  and 
Turbellaria  so  is  the  separation 
between  Turbellaria  and  Dis- 
toma  (sucking  worms)  not 
always  to  be  clearly  followed. 
There  are  free-living  Turbellaria 
with  suction  apparatus  but  no 
hooks,  which  are  only  service- 
able to  parasites.  Such  Tur- 

FIG.  32. — PLANARIA.  in-  IT  M         ^ 

„,      ,    ,     ,.  .    ™      .       bellana    could    easily    become 

Plan  of  a  free-living  Planaria.  J 

an,  eye  ;  ci,  cilia ;  D,  front    Parasites     (Ekto-parasites)      if 

main    intestine;      da,    branch 

of  same ;  Di,  left  rear,  and    they     could     thereby     obtain 

l)r,    right    rear     main     intes 

tine  ;    g,    brain ;    ge,    ger     nourishment  more  easily.     We 

minal      gland    ;    m,     mouth          _  .  .  , 

ph,    anus  ;  T,  feelers  ;  te     na ve  namely  supporting  e vidence 

testicle    bladder  ;  u,  ovarium;      -,          -,  .  •  i  •    i      i  i 

vi,  yolk  gland.  by  observation  which  shows  how 

'(After  von  Graff.)      opportunity    alone    may    render 

an  animal   a  facultative  parasite  whether  the  oppor- 
tunity be  artificially  or  spontaneously  provided. 

'  Thus    can  animals,   which  live  normally  in   the 
excreta    of  man,  also  develop  themselves   inside  the 


SUGGESTIONS  FOE  KELIABLE  HYPOTHESES     185 


8T. 


srn 


human  intestine  if  by  chance  their  eggs  find  their  way 

there  9 — as,  for  instance,  the  larvae  of  the  flies  Eristalis 

tenax  and  Anthomyia  canicularis.1 

The  worm  Leptodera  appendiculata 

lives  mostly    in  rotting  material 

in  the  soil ;   if  it  finds  entry  into 

the  hiding-place  of  a  snail  in  close 

vicinity    (which    thus    shares   its 

habitat)  it  can  also  flourish  there 

very  well. 

Certainly  by  such  examples 
nothing  is  shown  to  demonstrate 
how  a  parasite  by  opportunity 
only  may  become  a  true  one  which 
can  only  exist  in  a  definite  foreign 
organism.  We  can,  in  the  first 
place,  only  say  that  frequent  asso- 
ciation at  close  quarters  or  under 
similar  life  conditions,  can  often 
present  the  most  favourable  op- 
portunity, and  that,  with  the  ovary  ;  m'  mouth  ;  sb' 
change  of  the  mode  of  life,  the 


te 


FIG.  33. — DISTOMTJM. 

Plan  of  an  entoparasitic 
Distomum.  D,  anus  ;  Dl, 
lett,  and  Dr,  right  main 
intestine  ;  g,  brain  ;  ge, 


ventral  attachment  ;  sm, 
mouth  attachment  ;  te, 
testicles  ;  vi,  yolk  bag. 

instinct  of  the  animals  and  of  their     There    should    be    noted 

the 

offspring,     in    conjunction    with 


feeble      development 
of     the    intestinal    system 
.  .  (minus      outlet)     and     the 

their  conformation,  may  become     strength    of    the    genital 

.    n  -.  one.      The      sucker     is     a 

influenced.  positive  adaptation. 

The  best  example  how  shape- 
less forms  may  be  associated  with  normals — i.e.  those 
which    agree  with    a    definite    type — is    that   of    the 

1  Graff :    Wissenschaft  und  Bildung,  p.  9. 


186 


THE  THEORY  OF  EVOLUTION 


Copepods  (Swimming  Crabs).  Fig.  34  shows  some 
of  the  most  striking  transformations.  In  the  plant 
kingdom  parasitism  is  also  widely  extended.  Exclusive 

parasites  especially 
are  many  fungi  and 
bacteria  ;  they  are 
often  dependent 
upon  (  quite  definite 
animals  and  plants 
and  even  upon  nar- 
rowly limited  parts 
of  them/1  Often, 
however,  they  can 
find  their  nourish- 
ment  in  dead 
organic  remains  (sa- 
prophytes). 

With  the  Parasites 
in  the  series  of 
higher  plants  we  see, 
precisely  as  with 
animals,  a  feeble 
formation  or  a  per- 
fect absence  of  those 
organs  which  serve 
for  independent  nutrition — namely,  the  leaves  and  roots. 
The  non-chlorophyllic  leaves  of  the  Dodder  (Cuscuta 
Irifolii}  are  small  yellowish  scales.  With  many  tropical 
parasites  the  body  of  the  plant  is  reduced  to  the  flower, 

1  Strasburger  :  Lehrbuch,  p.  195. 


FIG.  34. — COPEPODA. 

1.  Free-living  Canthocamptus  minutus 
(after  Glaus)  :  la,  seen  from  the  side ;  Ib, 
nauplius  stage.  The  following  are  parasitic  ; 

2,  Carplouse  Argulus  foliaceus  (after  Glaus) ; 

3,  Achtheres  percarum,  female    (after  Glaus) ; 

4,  Chondr acanthus    gibbosus    (after     Glaus) ; 
Lerncsonema  monillaris ;    6.  Lernceocera   cyp- 
rinacea     (after     Nordmann)  ;    7,     Peroderma 
cylindricum,    (after   Riclitardi).      Explanation 
of  letters:     an,    antennae;  c,  tail;    ct,    main 
thorax;  k,  jaw;  kf,  jaw  foot;  o,  egg  sac  (in 
4  and  5,  only  partly  shown) ;  s,    sucker ;  t, 
breast    segments  ;    w,    suction     roots.      The 
figures     show,     from     left      to     right,     the 
graduated    transformation    of  the    Copepoda 
type    into    shapeless    bodies.       The    females 
show    only   still   the    characteristic    two    egg 
sacs  of  the  Copepoda.        (After  von  Graff.) 


SUGGESTIONS  FOR  RELIABLE  HYPOTHESES     187 

as  with  the  gigantic  flower  Rafflesia  Arnoldi  which 
is  seated  immediately  upon  the  roots  of  the  host  plant. 
Such  extreme  Parasites  can  no  longer  fulfil  the  main 
task  of  plants — viz.  that  of  assimilation  (i.e.  to  form 
organic  material  from  the  carbonic  acid  of  the  air  and 
the  water  and  salts  of  the  soil).  By  the  formation  of 
the  most  diverse  organs,  with  which  they  form  con- 
nections with  the  host  plants,  they  permeate  these  and 
also  in  most  cases  destroy  them. 

A  convincing  proof  cannot  certainly  be  produced 
that  the  parasites  pursued  formerly  another  and  inde- 
pendent mode  of  life.  Yet,  also  among  the  plants, 
we  have  some  indications  leading  to  this  assumption. 
Many  so-called  semi-parasites  like  Euphrasia,  Thesium, 
etc.,  possess  green  leaves  and  true  roots,  but  c  they 
attach  themselves  by  discs  or  wart-like  outgrowths 
to  the  roots  of  their  host  plants/  *  from  which  they 
draw  directly  water  and  nutritive  salts.  It  can  well 
be  assumed  that  the  opportunity  afforded  by  coming 
in  contact  with  other  roots  when  seeking  for  water 
gave  the  impulse  to  the  formation  of  sucking  apparatus. 
An  attraction  of  the  roothairs  towards  water,  whether 
in  the  soil  itself  or  in  the  roots  in  the  soil,  must  be 
assumed,  since  the  finest  rootlets  have  always  given 
the  impression  that  they  sought  for  humidity.  What, 
therefore,  was  formerly  caused  by  chance — namely  the 
formation  of  sucking  apparatus  in  the  said  semi-para- 
sites— may  gradually  become  a  permanent  tendency 
in  the  plants,  so  that  thus  the  Euphrasia,  which  cannot 

1  Strasburger :    Lehrbuch,  p.  42. 


188  THE  THEOKY  OF  EVOLUTION 

meet  with  other  roots,  can  now  nourish  itself  but  very 
imperfectly. 

(2)  Adaptive  phenomena  in  Symbiotics  (Ant  guests 
and  Termite  guests],  or  Myrmecophils  and 
Termitophils.1 

'  Ant  guests  and  Termite  guests  '  or  Myrmecophils 
and  Termitophils  are  those  Arthropods,  especially 
insects  and  mostly  beetles,  which  regularly  hve  in 
association  with  Ants  or  Termites.  Already  (in  1894) 
they  numbered  1419  species  ;3  at  present  they  may  be 
roundly  estimated  at  3000,  in  consequence  of  the  subse- 
quent great  advance  of  this  zoological  branch  of  research. 
We  find  in  these  animals  adaptations  of  the  most  diverse 
character  in  the  bodily  form  to  the  myrmecophil  or 
termitophil  mode  of  life.  In  the  first  place  we  find 
curious  beetles  provided  with  yellow  or  red  bunches 
of  hair  on  the  most  diverse  parts  of  their  bodies,  or 
with  other  '  exudatory  organs '  which  are  eagerly 
licked  and  cared  for  by  the  Ants  or  Termites,  and  the 
beetles  are  often  fed  from  their  mouths  ;  these  constitute 
the  so-called  Symphil  type  or  '  true  guest  type/  Others 
of  these  guests  show,  in  bodily  form  and  colour,  often 
also  in  the  form  of  the  antennae,  a  striking  resemblance 

1  It  appeared  to  us  better,  by  one  thoroughly  treated  instance,  to  make 
the  chain  of  evidence  clear  to  the  reader,  rather  than  to  give  a  purview 
of  the  whole  of  the  observation  material.     The  study  of  the  Ant  and 
Termite  guests  belongs  to  the  special  domain  of  P.  E.  Wasmann,  who  has 
occupied  himself  with  the  study  for  decades.     The  following  remarks 
are  entirely  from  his  pen  and  were  written  specially  for  this  work. 

2  Wasmann  :    Kritisches   Verzeichnis  der   myrmekophilen   und  termito- 
philen  Arthropoden. 


ANT  AND  TERMITE  GUESTS  189 

to  their  hosts,  to  whom  they  present  themselves  also  as 
their  equals  ;  these  belong  to  the  Mimicry  type  which, 
especially  in  many  of  the  associated  beetles  (Staphy- 
linidse)  of  the  wandering  ant  of  the  Old  and  New  World, 
show  an  astonishingly  high  perfection.  Other  guests, 
finally,  clothe  themselves  in  armour  impenetrable  by 
the  ant  beetles,  in  order  thus  to  be  able  to  live  in  their 
company  ;  these  form  the  offensive  (Trutz)  type  of  the 
Ant  and  Termite  guests,  etc.1  The  relation  of  the  said 
facts  to  the  theory  of  evolution  is  briefly  stated  as 
follows,  abstaining  from  discussing  the  causes  (internal 
and  external)  of  the  evolution  and  also  the  manner 
of  it  (fluctuating  variation,  mutation,  etc.). 

The  myrmecophil  and  termitophil  adaptive  charac- 
ters with  which  we  meet  in  various  classes  of  insects — 
millipedes,  spiders,  crustaceans,  and  in  the  various 
organs  of  these  classes,  especially,  however,  in  the  insect 
orders  of  the  Beetles  and  Diptera — convert  the  forms 
concerned  into  proper  systematic  species,  proper  genera, 
and  often  even  into  proper  sub-families  or  families 
which  differ  widely  from  their  systematic  relatives 
which  do  not  associate  with  Ants  or  Termites. 

These  differences,  however,  are  only  to  be  explained 
by  assuming  that  in  the  course  of  race  development  by 

1  For  more  details  see  Wasmann  :  Die  Myrmekophilen  und  Termito- 
philen,  Ley  den,  1895  (Verh.  des  dritten  Internationalen  Zoologencongr  esses)  ; 
Die  moderne  Biologie  und  die  Entwicklungstheorie  (1906),  chap.  x.  ;  Der 
Kampf  umdas  Entwicklungsproblem  in  Berlin  (1907).  1  Vortrag ;  Beispiele 
rezenten  Artenbildung  bei  Ameisengdsten  und  Termitengasten  (Festschrift  far 
.Rosenthal  Biolog.  Zentralblatt,  XXVI  (1906),  Nos.  17  and  18  ;  Die  progressive 
Artbildung  und  die  Dinardaformen  (Natur  und  Offenbarung  (1909),  part  6) ; 
Wesen  und  Ursprung  der  Symphilie  (Biolog.  ZentralbL,  XXX  (1910), 
Nos.  3-5). 


190 


THE  THEOKY  OF  EVOLUTION 


adaptation  of  the  said  insects,  etc.,  to  the  myrmecophil 
or  termitophil  mode  of  life,  they  have  developed 
themselves.  Thus  do  the  adaptive  phenomena  among 
the  Ant  guests  and  Termite  guests  afford  in  fact  an 
abundance  of  evidence  in  favour  of  the  generic-historical 
appearance  of  new  species,  new  genera,  new  groups  of 
genera,  and  new  families  in  the  animal  kingdom. 

In  support  of  the  above  paragraph  we  will  give  only 
a  few  examples.    In  the  Beetle  family  of  the  Staphylids 

we  find  in  the  group  of  the 
Lomechusini  three  genera  with 
altogether  twenty-one  species, 
which,  by  their  peculiarly 
broad  bodily  form  and  the 
arched  sides  of  the  thoracic 
shield,  and  particularly  by  the 
yellow  bunches  of  hairs  on  the 
hinder  sides  of  the  body,  differ 
strikingly  from  the  rest  of  the  Staphylids  (Fig.  35). 
All  these  morphological  peculiarities  are  adaptive 
characters  to  the  true  guest  relations  which  connect 
those  beetles  with  the  ants.  The  myrmecophil  adaptive 
characters  form,  therefore,  the  particular  reason  why 
these  beetles  form  proper  species,  proper  genera,  and 
a  proper  group  of  genera  of  the  Staphylids. 

Furthermore  we  know  so  far  of  over  one  hundred 
genera,  with  about  five  hundred  species,  in  the  family 
of  the  Staphylidse  alone,  of  Ant  guests  or  Termite 
guests,  whose  systematic  separation  also  depends  upon 
their  myrmecophil  or  termitophil  adaptive  characters. 


FIG.  35. — LOMECIIUSA  STBUMOSA 
F.  (mag.  5  diarri.)- 


ANT  AND  TERMITE  GUESTS  191 

Many  of  these  genera — as,  for  instance,  the  Mimeciton 
(Ant  Ape)  belonging  to  the  mimicry  type  of  the 
Dorylinae  guests — are  by  their  adaptive  characters  so 
extremely  different  from  their  other  family  relatives, 
that  a  systematic  sub-family  can  be  justly  based  upon 
them,  as  has  been  done  also  for  the  offensive  type 
(Trutztypus)  of  the  genera  belonging  to  the  Dorylin 
guests,  Trilobitideus,  Xenocephalus,  and  Pygostenus, 
which  represent  the  typical  genera  of  the  sub-families 
Trilobitideini,  Xenocephalini,  and  Pygostenini.  Very 
remarkable,  too,  are  the  termitophil 
Physogastric  Aleocharince  (Fig.  36), 
Staphylinids  with  enormously  de- 
veloped, mostly  membraneous  pos- 
teriors, which  can  assume  the  most 

FIG.  36.— TEEMITOBIA 

grotesque  forms   and   most   singular        ENTENDVENIENSIS 

TnAG.(mag.5diam.) 

positions,  as,  for  instance,  in  the 
genera  Spimcktha,  Termitobia,  and  Termitomimus.  Until 
now  twenty-four  genera,  with  thirty-two  species,  have 
been  discovered  of  these  interesting  creatures  in  the 
tropical  termite  nests  where  they  are  eagerly  licked  by 
their  hosts  on  account  of  the  exudation  of  agreeable 
secretions  which  here  are  an  element  of  the  blood  fluids 
of  the  guests,  and  in  return  are  fed  from  their  hosts' 
mouths,  as  is  evident  from  the  formation  of  the  tongues 
of  the  beetles  concerned.  The  morphological,  generic, 
and  specific  characters  of  these  hemiptera  show  them- 
selves thus  to  be  termitophil  adaptive  characters. 

There  is  also  a  particular  family  or  sub-family  of 
small   myrmecophil   beetles  which   have    been  named 


192  THE  THEORY  OF  EVOLUTION 

Club  Beetles  (Clavigeridae)  on  account  of  the  peculiar 
form  of  their  antennae.  These  differ  from  their  nearest 
relatives,  the  '  Feeler  Beetles  '  (Pselaphiden)  by  a  series 
of  adaptive  characters  fitted  for  the  true  guest  conditions ; 
by  the  marked  development  of  the  first  upper  rear 
segments,  which  bear  a  broad  and  deep  exudation  groove; 
by  the  yellow  hair  bunches  on  the  hinder  parts  at  the 
sides,  or  on  the  wing  cover  points ;  by  the  shortened, 
thickened,  and  very  variedly  formed  antennae,  as  also 
by  the  retrogression  of  the  feelers  which,  as  organs  of 
independent  search  for  nutrition,  have  become  useless. 
Classic  examples  of  Club  Beetles  are  our  small  yellow 
ones  (Claviger  testaceus)  as  are  the  great  Madagascar  Club 
Beetles  with  stag-horn  feelers  (Mirodaviger  cervicornis). 
We  know  already  at  present  forty-two  systematic  genera 
of  Clavigeridse  with  124  species,  whose  generic  and  family 
characters  are  plainly  myrmecophil  adaptive  characters. 
There  is,  furthermore,  one  particular  beetle  family— 
the  Paussidse  or  Feeler  Beetles — which  are  all  Ant  guests 
but  nevertheless  belong  to  different  biological  classes. 
By  far  the  most  of  them  are  true  guests  which  are 
provided  with  multiform  reddish  yellow  hair  bundles, 
exudation  grooves,  and  exudation  pores  which  are  licked 
by  their  hosts.  Their  very  thick  and  only  two-limbed 
feelers  present  the  most  varied  and  grotesque  forms, 
which,  however,  all — like  the  exudatory  organs  just 
mentioned — stand  in  the  most  intimate  connection 
with  their  true  guest  relationship.  The  species  and 
genera  of  the  Paussidse  and  the  whole  family  itself  are 
what  they  are  by  virtue  of  their  myrmecophil  character. 


ANT  AND  TERMITE  GUESTS 


193 


We  know  so  far  333  living  species,  divided  over  sixteen 
genera.  In  addition  there  are  five  extinct  species,  of 
which  four  lived  in  the  lower  Oligocene  and  therefore 
in  the  first  third  of  the  Tertiary  period.  Three  of 
them  belong  to  the  still  living  genera  Arthropterus  and 
Paussus ;  one,  Paussoides,  is  only  known  as  a  fossil. 
There  is  also  a  Paussus  of  the  Diluvial  period  (pre- 
served in  Copal).  The  Paussidae  show  the  nearest 
systematic  relationship  with  the  Carabidae  and  with 
the  group  of  Bombardier  beetles  (Brachyninae)  to 
which  the  most  primitive  Paussidae  genera  closely 
approach.  Since  the  Carabidae  appeared  already  in 
the  Trias  and  in  the  Lias  and  since  the  Brachyninae 
are  already  represented  in  the  upper  Chalk  and  the 
lower  Oligocene,  hence  they,  palaeontologically,  are 
to  be  assumed  as  the  ancestors  of  the  Paussidse. 

As  with  the  Staphylinidae,  Clavigeridae,  and  Paussidse 
so  it  is  with  the  Gnostidae,  Ectrephidae,  Pselaphidae, 
Scydmaenidae,  Thorictidae,  Rhysopaussidae,  Endomy- 
chidae,  Silphidae,  Lathridiidae,  Histeridae,  Scarabaeidse 
Brenthidae,  etc.,  which  partly  represent  some  myrme- 
cophil  or  termitophil  families  or  sub-families  and  partly 
embrace  a  larger  or  smaller  number  of  myrmecophil 
or  termitophil  genera  and  species,  whose  systematic 
characters  attribute  themselves  as  adaptive  characters 
to  the  myrmecophil  or  termitophil  mode  of  existence. 

Furthermore  we  find  also  in  the  insect  order  of  the 
Diptera  or  two-winged  flies  a  series  of  similar  examples. 
The  Termitoxeniidae  form  a  special  family  (or  sub- 
family) which  embraces  exclusively  Termite  guests, 


194 


THE  THEORY  OF  EVOLUTION 


of  which,  two  genera  (Termitoxenia  and  Termitomyia), 
not  only  in  their  entire  form  of  body,  but  also  in  their 
development  and  mode  of  reproduction,  strikingly 
differ  not  only  from  all  other  Diptera  but  even  from 
all  other  insects.  They  possess,  namely,  no  larval 
form,  but  effect  their  post-embryonal  metamorphosis 
in  the  form  of  a  peculiar  '  imaginal  evolution  '  (Fig.  37). 
Also  the  individuals  are  not  sexually  separated,  but 
are  regularly  protandric  hermaphrodites — a  unique  case 
in  the  insect  world.  All  the  morphological  and 
morphogenetic  (embryological)  characters  of  this 
remarkable  Diptera — of  which  so  far  six  species  are 
known — show  themselves  to  be  termitophil  adaptive 
characters. 

Furthermore  among  the  termitophil  Diptera  must 
be  mentioned  the  Termitomastini,  which,  although 
belonging  to  another  sub-order  of  the  Diptera — the 
Termitoxemni  are  short-horned,  the  Termitomastini 
long-horned — present  many  similarities  to  them.  Also 
the  Termitomastini  owe  their  systematic  separation 
entirely  to  their  adaptive  characters  fitting  them  for 
a  termitophil  existence. 

A  very  interesting  example  of  termitophil  trans- 
formation is  furthermore  shown  in  the  genus  Thauma- 
toxena  belonging  to  the  Diptera  family  of  Phoridse. 
Therein  we  find  that  even  the  organization  characters 
of  the  two- winged  order  are  so  greatly  masked  by  the 
termitophil  adaptation,  that  two  excellent  insect  experts, 
Breddin  and  Borner,  described  the  first  species  of 
this  genus  Thaumatoxena  Wasmanni  originally — not 


ANT  AND  TEEMITE  GUESTS 


195 


as  a  Diptera  but  as  a  new  genus,  of  the  Rhynchotae — 
which,  however,  form  quite  another  order  of  insects. 

We  must  also  mention  here  the  myrmecophil  wing- 
less Diptera  genera  Aenigmatias  and  Oniscomyia,  which 
resemble  rather  a  Blattid  of  the  order  of  Orthoptera 
or  a  small  Isopod  than  a  fly — and  this  again  through 
the  adaptation  of  characters  to  the  myrmecophil  mode 
of  life  to  which  they  owe  their  systematic  peculiarities. 
Also  among  the  other  Diptera  we  meet  with  many 
myrmecophil  genera,  such 
as  Microdon,  Ephippomyia, 
Harpagomyia,  etc. 


FIG.  37. — PHYSOGASTRE  IMAGO  OF 
Termitoxenia  Assmuihi. 

(After  Wasmann.) 


We  come  now  to  the  under- 
lying principle  of  the  above 
examples.  It  is  based  on  the 
evidence  of  palaeontology, 
comparative  morphology  and 
biology,  and  the  individual 
evolutionary  history. 

(a)  Palaeontology  shows  us  that  the  systematic  orders 
of  the  Arthropods,  to  which  the  Ant  guests  and  Termite 
guests  belong,  appeared  very  much  earlier  in  the  world's 
history  than  the  Ants  and  Termites  themselves.  Thus, 
so  we  conclude,  the  guests  belonging  to  those  older 
Arthropod  orders  could  not  be  absolutely  '  created  ' 
for  their  later-coming  hosts,  but  have  only  later  been 
evolved  by  way  of  natural  evolution  out  of  originally 
independent  living  forms  by  adaptation  to  the 
myrmecophil  or  termitophil  mode  of  life  into  the 

o2 


196  THE  THEOKY  OF  EVOLUTION 

systematic  species,   genera,  and    families   such   as   we 
find  to-day. 

An  example  out  of  the  class  of  insects  we  give  in 
more  detail.  The  order  of  the  Beetles  appeared  geo- 
logically already  in  the  beginning  of  the  Mesozoic 
group  of  formations  in  the  Trias,  where  it  is  represented 
by  about  twenty  genera.  Altogether  352  Mesozoic  species 
of  beetles  have  long  since  been  found.1  The  order  of 
the  Termites  (Isopterae)  appears,  however — so  far  as 
hitherto  can  be  certainly  known — first  in  the  beginning 
of  the  Tertiary  period,  therefore  at  the  commencement 
of  the  Csenozoic  group  of  formations  :  in  the  Eocene  we 
find  first  one  species,  in  the  Oligocene  twenty -five,  in  the 
Miocene  twenty-nine.  The  family  of  the  Ants  of  the  order 
of  Hymenoptera,  so  far  as  can  be  certainly  known,  first 
appeared  in  the  lower  Oligocene — thus  in  the  older 
Tertiary  period :  in  the  Oligocene  there  are  121,  in  the 
Miocene  174  species — which  for  fossil  insects  is  a  very 
large  number.2  In  any  case  we  see  from  this  that 
both  the  Ants  and  the  Termites  only,  in  the  beginning 
of  the  Tertiary  period,  became  a  power  in  the  household 
of  the  world,  which  was  the  essential  preliminary  con- 
dition for  the  adaptation  of  other  insects  to  the  mode 
of  existence  in  the  nests  of  the  Ants  and  Termites.  We 
must  therefore  necessarily  assume  that  the  myrmecophil 
and  termitophil  species,  genera,  and  families  of  the 
Beetles  either  were  first  subsequently  created  in  the 
Tertiary  period — and  that  means  each  species,  genus, 

1  Handlirsch  :   Die  fossilen  Inseckten,  pp.  398,  1171. 

2  Ibid.  1182,  1185. 


ANT  AND  TERMITE  GUESTS 


197 


and  family  of  guests  for  a  particular  '  normal '  host 
species,  host  genus,  and  host  family,  and  this  at  the 
same  time;  or  we  must  assume  that  they,  by  the  way 
of  a  natural  racial  evolution,  by  adaptation  to  the 
myrmecophil  and  termitophil  mode  of  existence,  arrived 
at  that  which  they  represent  in  systematic  classifi- 
cation— namely,  particular  species,  genera,  and  families. 
The  first  assumption,  however,  gives  no  natural  explana- 
tion whatever  of  the  origin  of  adaptive  characters,  but 
is  an  obvious  denial  of  the  same  ;  therefore  the  latter 
assumption  remains  as  the  only  natural  explanation 
of  the  facts  concerned. 

For  the  further  elucidation  of  this  evidence  it  may 
be  furthermore  mentioned  that,  for  instance,  the  various 
species  of  the  wandering  Ant  genus  Eciton  in  Brazil 
have  not  only  various  species,  but  even  very  many 
varied  genera  of  Hemiptera  as  guests,  which  are  only 
adapted  to  this  kind  of  host.  This  applies  namely 
to  the  guests  of  the  mimicry  type  which  are  extra- 
ordinarily specialized.  Thus,  for  instance,  the  genus 
Mimeciton  is  only  fitted  for  existence  for  and  with  Eciton 
prcedator,  the  genus  Ecitoxenia  only  for  and  with 
Eciton  quadriglume,  the  genus  Ecitophya  (Fig.  38) 
only  for  and  with  Eciton  Burchelli  (Foreli),  etc. ;  and, 
in  addition,  the  species  concerned  of  the  host  genus 
Eciton  are  very  closely  related  and  partly  so  closely 
resemble  each  other  that  a  constancy  theorist  could 
only  regard  them  as  '  races '  of  one  and  the  same 
species  and  would  therefore  not  require  for  them  a 
special  '  creative  act/  but  the  guests  God  must  have 


198  THE  THEORY  OF  EVOLUTION 

'  created   specially/      The  futility   of  this  assumption 
is  obvious. 

(b)  The  second  source  of  evidence  for  the  underlying 
principle  is  to  be  derived  from  the  facts  of  comparative 
morphology  and  biology,  and  specially  from  the  examples 
of  recent  formation  of  species  which  we  have  derived 
from  a  series  of  works  on  the  Ant  guests  and  Termite 
guests.  We  find,  namely,  still  in  the  present  time 
clear  traces  of  a  formation  of  '  new  species  '  in  this 


FIG.  38. — Ecitophya  simulans  Wasm. 
(S.  Catharina,  Brazil ;    mag.  5  diam.) 

domain  of  research.     Two  of  such  examples  must  here 
suffice  to  be  mentioned. 

Within  the  hemipterous  genus  of  Dinarda  we  find 
a  series  of  bicoloured  (red  and  black)  '  forms  '  which 
live  with  various  species  of  the  Ant  genus  Formica 
in  Europe  and  Asia  and  are  so  adapted  to  them  that 
they  regulate  themselves  as  regards  their  size  and 
coloration  according  to  those  of  their  particular  host 
Ant  species.  Two  of  these  forms — Dinarda  dentata 
and  Markeli — which  live  with  Formica  sanguined  and 
Formica  rufa  respectively,  cannot  already  be  dis- 
criminated from  so-called  '  good  species/  and  occur 
also  throughout  the  whole  domain  occupied  by  their 


ANT  AND  TEBMITE  GUESTS  199 

hosts.  Two  others,  on  the  other  hand — Dinar  da  Pygmcea 
and  Hagensi — which  live  with  Formica  rufibarbis  and  F. 
exsecta  are  only  on  the  way  to  develop  :  they  appear, 
for  instance,  only  in  a  limited  portion  of  the  domain 
occupied  by  their  hosts  and  in  their  typical  form, 
outside  of  which  they  are  absent  or  are  replaced  by 
transitional  forms  which  have  arisen  from  Dinarda 
dentata  ;  they  stand  thus  as  outposts  at  different  stages 
of  species  formation,  always  according  to  the  various 
points  of  their  extensive  domain.  In  this  way  we 
conclude  that  there  is  being  perfected  before  our  eyes 
a  so-called  process  of  species  formation  within  the 
genus  of  Dinarda.1 

The  same  causes  of  adaptation  which  at  present 
still  determine  the  process  of  differentiation  between 
our  northern  bicoloured  Dinarda  forms,  suffice,  how- 
ever, perfectly  to  explain  the  systematic  differences 
which  exist  between  the  genus  Dinarda  and  the  closely 
related  therewith  Mediterranean  genus  Chitosa.  The 
host  ant  of  the  latter  is  namely  Aphcenogaster  testaceo- 
pilosa,  thus  belonging  to  quite  another  sub-family 
of  the  Ant  stock  (Myrmicini)  belonging  to  the  Formica 
(Camponotoni).  The  adaptation  of  an  Aleocharina 
of  the  offensive  type — such  as  are  Dinarda  and  Chitosa 
to  Formica  on  the  one  hand  and  to  Aphsenogaster 
on  the  other — demands,  however,  much  greater  morpho- 
logical differences  than  the  adaptation  to  different 

i  The  objections  raised  by  H.  Muckermann  in  Natur  und 
Offenbarung,  1909,  No.  1,  have  already  been  contested  by  me  therein 
in  No.  6. 


200  THE  THEOKY  OF  EVOLUTION 

species  of  one  and  the  same  genus  of  host  Ants.  It  is 
therefore  easily  comprehensible  that  the  differences 
between  Dinarda  and  Chitosa  can  be  raised  to  the 
value  of  generic  distinguishing  characters,  while  those 
between  the  various  bicoloured  Dinarda  forms  attain 
at  the  highest  the  value  of  specific  characters.  Thereby 
is  the  demonstrative  power  of  the  argument  deduced 
from  the  evolution  of  our  Dinarda  forms  also  extended 
to  the  genera  of  Dinarda  and  Chitosa. 

A   second   example,   but   certainly   of   only   recent 
species  formation,  is  presented  by  the  transformation 
of  East  Indian  and  African  Wandering  Ant  guests  into 
Termite   guests.     Within    the   hemipterous   genera    of 
Doryloxenus    and    Pygostenus,    whose    entire    generic 
types  are  only  to  be  explained  by  adaptation  to  the 
mode  of  life  of  Wandering  Ants  (Dorylus  and  sub-genus 
Anomma),  there  are  found  namely  amongst  numerous 
dorylophil  species  also  a  few  termitophils  which,  together 
with   the   generic   characters   which   indicate   Dorylus 
guests    of    the    offensive    type,    show   special   specific 
characters,  which  render  them  proper  termitophil  species. 
Since,   however,  we  can  only  explain  the   systematic 
generic  characters  of  these  hemiptera,  which  belong  to , 
the    sub-family   of   the  Pygostenini,  by  adaptation  to 
the  dorylophil  mode  of  existence  (see  above,  p.   191), 
we  must  logically  explain  the  specific  characters  which 
deviate  from  the  dorylophil  relatives,  and  are  shown 
by  the  few  termitophil  species  as  follows,  viz.  :  that 
these,  geologically  speaking,  in  quite  recent  times,  have 
become  transferred  from  the  mode  of  life  with  Wandering 


ANT  AND  TERMITE  GUESTS  201 

Ants  to  that  of  the  Termites,  and  have  thereby  become 
new  systematic  species,  since  they,  as  a  consequence 
of  their  new  mode  of  life,  assumed  characters  by  which 
they  approach  the  rest  of  the  termitophil  Aleocharinse 
of  the  offensive  type  of  the  genera  Discoxenus,  Termito- 
discus,  Termitusa,  Termitopsenius,  etc. 

Since,  in  addition,  Wandering  Ants  by  preference 
attack  and  plunder  Termite  nests  and  on  such 
occasions  are  also  accompanied  by  their  guesfcs  of 
the  genera  Doryloxenus  and  Pygostenus — the  first 
riding  on  the  Ants,  the  latter  going  on  foot — from 
the  biological  standpoint  it  is  also  easily  explained 
how  this  transformation  of  originally  dorylophil 
species  to  a  termitophil  mode  of  life  has  been  brought 
about. 

(c)  A  third  proof  of  the  underlying  principle  of  our 
evidence  is  seen  in  the  individual  evolutional  history 
especially  of  Termitoxenia.  This  hemipterous  genus 
possesses,  namely,  peculiar  staff-shaped  dorsal  growths, 
which  it  is  true  stand  on  the  site  of  former  wings,  but 
are  entirely  useless  for  flight,  while  they  serve  various 
other  biological  purposes,  such  as  feeling  organs, 
transport  organs  by  aid  of  the  hosts,  and  as  exudatory 
organs.  That,  however,  these  enigmatical  structures 
were  originally  wings,  that  thus  the  wingless  Termi- 
toxenia have  arisen  from  normally  winged  Diptera,  can 
still  be  shown  to-day  by  the  individual  development 
of  these  thoracic  attachments  ;  since  they  still  show,  in 
a  certain  youthful  stage  of  the  animal,  the  form  of 
wing  flaps  with  a  clear  wing  venation,  which  are  later 


202  THE  THEORY  OF  EVOLUTION 

absorbed  and  changed  into  the  staff-like  attachments.1 
We  have  thus  also  in  the  individual  development 
strong  evidence  of  the  probability  of  the  evolution 
of  this  genus  from  the  original  stock. 

By  the  above  our  concluding  principle  is  also 
established,  viz.  that  the  adaptive  phenomena  in  the 
Ant  guests  and  Termite  guests  provide  an  abundance 
of  evidence  of  the  generic  historical  evolution  of 
new  species,  genera,  and  even  families  in  the  animal 
kingdom — i.e.  their  evolution  from  the  original  stocks. 

§  3.  Suggestive  points  in  the  Embryogeny  of  the  present 

organisms. 

(1)  Premises     and     extent     of     the     embryological 
evidence. 

We  have  seen  that  even  to-day  causes  are  active 
which  can  lead  to  the  most  multifarious  transformations 
of  animals  and  plants.  Thereby  is  clearly  shown  that 
the  germ  cells  of  the  altered  forms  are  also  influenced. 
We  will  elucidate  this  by  a  simple  example.  If  a  plant 
be  transplanted  from  a  valley,  its  usual  habitat,  to 
an  elevation  of  considerable  height,  there  arise  various 
adaptive  characters  :  the  plant  produces,  for  instance, 
hairs  as  a  protection  from  cold,  its  leaves  become  very 
rich  in  chlorophyll  (intensely  green)  in  order  to  assimilate 
more  vigorously  during  the  shorter  period  of  vegetative 
activity ;  thereby  the  whole  habit  of  the  plant  can  be 

1  See   Wasmann  :     Die    ThorakalanMnge  der   Termitoxeniidce  ( Verh. 
der  Deutschen  Zoologischen  Gesellschaft,  1903). 


EMBRYOGENY  203 

greatly  altered.  If,  now,  after  some  vegetative  periods 
the  seed  of  such  purposely  adapted  '  alpine '  plants  be 
sown  again  in  the  valley,  there  is  shown  in  the  resulting 
individuals  a  strong  tendency  to  retain  the  '  adaptive 
characters/ 

Obviously  in  this  case  the  formation  of  the  seed 
(the  embryo)  alone  was  under  the  influence  of  the 
elevated  position :  the  entire  growth  of  the  plant 
itself  occurred  in  the  valley.  What,  therefore,  still 
appears  of  the  alpine  character — and  that  in  the  first 
generation  is  fairly  considerable — was  established  in 
the  seed  (embryo)  and  therefore  already  in  the  ovum. 

In  other  words,  the  entire  embryonic  development 
is  so  fashioned  that  it  no  longer  strives  towards  the 
earlier  forms  but  rather  towards  the  newly  acquired 
adult  ones. 

This  applies  exactly  to  the  other  cases  :  if  the 
alterations  which  mostly  appear  in  the  full-grown 
complete  forms  have  arisen  by  parasitism,  by 
particular  modes  of  life,  by  isolation,  etc.,  the  embry- 
onic development  is  always  influenced  ;  if  it  were  not,  the 
changed  adult  forms  could  not  present  themselves  at  all. 

The  deeper  the  transformation  of  the  entire  organism 
may  be  which  it  needs  in  order  to  become  adapted  to 
its  new  mode  of  life,  the  greater  will  its  embryonic 
evolution  differ  from  the  earlier  one.  The  more  trifling 
it  is,  the  less  also  will  the  embryogeny  be  altered. 
Furthermore,  there  are  visible  the  alterations,  in  those 
germ  stages  in  which  the  organs  commence  to  form, 
which  are  specially  designed  for  service  under  the 


204 


THE  THEOKY  OF  EVOLUTION 


new  life  conditions  ; l  for  the  rest  the  germ  development 
will  proceed  as  hitherto.  If  now  this  unaltered  re- 
mainder is  so  constituted  that  there  can  be  clearly 
perceived  in  it  a  mode  of  evolution  peculiar  to  a  deter- 
mined type,  then  we  must  regard  the  animal  concerned 
as  a  member,  as  a  variation  of  that  type.  By  what 

causes  the  deviations  in 
the  completely  formed 
condition  and  in  the 
embryonic  stages  lead- 
ing thereto  are  induced 
can  then  under  some 
circumstances  be 
directly  seen.  If  the 
larva,  for  instance, 
attaches  itself  firmly 
and  at  once  commences 
the  transformation 
which  strikes  us  in  the 
perfect  animal,  then 

FIG.  39.— BARNACLE      IN      ITS    FORMS  OF  ,1  •        -j-rr,-ncjfnrma 

DEVELOPMENT.  was 

tion    formerly    caused 

for  the  first  time  by  transfer  of  the  animal  to  a  sessile 
mode  of  life. 


1  With  regard  to  the  time  in  which  the  separate  tissues  and  organs 
became  differentiated  during  the  embryonic  development,  there  are  often 
great  differences  in  the  separate  groups  of  animals.  Biologists  define 
two  great  groups,  the  mosaic  and  the  regulation  ova,  according  to  the  earlier 
or  later  commencement  of  the  differentiation  and  the  therewith  connected 
greater  or  lesser  facility  of  the  '  regulation  '  (restitution)  in  the  embryos 
produced  from  the  eggs. 


EMBKYOGENY 


205 


(a)  A  few  examples  will  make  this  more  compre- 
hensible. On  driftwood  and  sunken  piles  there  is  often 
found  a  mussel-like  animal  attached  by  a  stalk — 
the  Barnacle  (Lepas  anatifera,  L.)  (Fig.  39).  Formerly 
they  were  regarded  as  mussels,  although  even  on  a 
superficial  examination  much  is  perceived  which  is 
not  exactly  mussel-like,  as  for  instance  the  possession 
of  numerous  movable  limbs,  the  clasping  feet  (Ran- 
kenfiisze). 

The  most  remarkable  thing  is  that  from  the  eggs 
of  this  animal  crab  larvae  issue  of  the  so-called  '  Naup- 
lius  '  type.     The  Nauplius  larva  is  an  embryonic  stage 
common  to  all  the  lower  crabs  (Entomostraca).     After 
a  definite  time  the  larva  attaches  itself  by  its  own  ten- 
tacles  to  a  support,  lime  is  deposited    in  the   shell, 
the  head  becomes  a  stalk,  the  eye  is  aborted,  the  swim- 
ming feet  become  clinging  feet  (which  serve  to  whirl 
food  within  reach  but  not  for  locomotion),  and  the 
Barnacle  is  complete.1     On  close  examination  we  see 
certainly  also,  in  the  adult  form,  still  other  true  crab- 
like   characters,   as    for   instance   in   the    construction 
of  the  mouth,  the  nervous  system,  the  legs,  etc.     In 
short  there  remains  everything  of  a  crab  type  :   in  the 
first  place  the  embryogeny  up  to  that  stage  where  such 
constructions  were  added,  the  positive  adaptations  to  the 
sessile  mode  of  life,  and  furthermore  all  the  characters 
of  the  Cirripedia,  which  also  can  be  of  service  in  their 
old  form  in  the  new  mode  of  life — jaws,  nerve  system, 
and  make  of  the  legs.     In  other  cases  certainly  it  is 

1  Heffe  :   Abstammungslehre  und  Darwinismus,  p.  30. 


206 


THE  THEORY  OF  EVOLUTION 


only  the  embryonic  development  which  now  gives  a 
clue  to  the  systematic  relationship — for  instance  with 
Sacculina  carcini,  the  female  of  which  finally  becomes 
an  egg-bag  which  pervades  the  whole  body  of  its  host 
animal  (a  crab)  with  a  cotton-like  web.  The  embryonic 
development  on  the  other  hand  is  that  of  the  Cirripedia 
(Figs.  40  and  41).  From  all  this  we  conclude,  and,  as 


FIG.  40. — CIRRIPEDIA.  Sacculini  carcini  (after 
Delage).  1.  Second  Nauplius  stage.  2,  3.  The 
same  after  attachment  of  the  breast  piece  and 
loss  of  tail.  4.  The  bottle-like  stage  passing 
into  the  interior  of  the  crab.  5.  The  final 
stage. 

Letter  reference:  an,  antennae;  an,  eye;  c, 
tail  ;  cp,  anus  ;  kr,  main  shield  of  the  crab  ;  r, 
the  cell  tube  of  the  Sacculina  larva  penetrating 
the  host ;  s,  Sacculina  externa ;  z,  central  cell 
mass.  (After  von  Graff.) 

it  appears  to  us,  with  entire  right,  that  the  Lepas  species 
were  formerly  free-swimming  crabs  which  subsequently 
adopted  a  sessile  existence.  Their  embryogeny  alone 
and  the  still  remaining  crab  characters  show  us  clearly 
the  true  nature  of  the  Barnacles.  The  whole  group 
of  the  Cirripedia  behaves  in  a  similar  manner.  Very 
remarkable  beings  are  also  the  animals  known  as 
Parasitica  which  as  parasites  live  especially  on  fish, 
upon  whose  skin  or  gills  they  attach  themselves  by 


EMBRYOaENY 


207 


suckers.  They  were  formerly  considered  as  worms 
or  articulate  animals,  until  their  embryogeny  became 
known.  '  They  possess  an  amorphous  body  in  which 
often  nothing  of  limb  formation  remains  and  only  a 
trace  of  extremities  can  be  found/  l  Some  characters, 


FIG:  41. — Sacculini  carcini,  fixed  onCarcinus 
mcenas,  whose  abdomen  is  exposed.  a, 
eye  ;  b,  antennae  ;  c,  anus  of  crab  ;  d,  shell 
opening ;  e,  stalk ;  f ,  root  of  web,  envelop- 
ing the  intestines  of  the  host,  leaving 
the  germinal  region  free. 

(After  Hertwig  :  '  Zoologie.') 

which  remind  one  of  free-living  Swimming  Crabs  (two 
suspended  egg  sacs),  furthermore  a  series  of  transitional 
forms  between  Swimming  Crabs  and  these  amorphous 
beings,  and  above  all  their  evolutionary  history  (em- 
bryogeny)— these  were  the  factors  which  cleared  up 
their  systematic  position.  They  pass  through  the 
typical  Cyclops  stage  of  the  Copepods,  and  only  when 

1  R.  Hertwig  :   Lehrbuch,  p.  382. 


208 


THE  THEORY  OF  EVOLUTION 


the  females,  and  only  the  females,  attach  themselves 
after  the  pairing,  do  the  retrogressive  steps  begin  which 
lead  to  the  assumption  of  the  almost  limbless  state. 
The  males  remain  much  more  crab-like,  they  die  after 
the  pairing,  their  function  being  fulfilled  ;  the  females, 
on  the  other  hand,  must  now  provide  the  eggs  with 
nutrition,  and  therefore  survive.  Since  they  can  do 


FIG.  42. — Young 
Flounder  be- 
fore the  shift- 
ing of  the  eye. 
(mag.40diam.) 


FIG.  43.  —  Flounder 
when  eye  is  quite 
shifted. 


FIG.  44.  —  Commence- 
ment of  the  shifting 
in  the  Turbot.  (mag. 
10  diam.) 


that  as  parasites  without  organs  of  locomotion  or 
sense,  these  abort  as  superfluous.  They  were  therefore 
at  first  Rudder  Crabs  (Ruderkrebse)  in  their  appear- 
ance, as  the  males  still  are,  and  their  amorphous  form 
is  no  original  one,  but  one  acquired  by  parasitism. 

Many  similar  examples  might  be  quoted — as,  for 
instance,  the  transfer  of  the  right  eye  to  the  left  side 
in  the  young  of  flatfish  which,  as  adults,  lie  on  the  right 
side  and  have  both  eyes  on  the  left  side  (Figs.  42,  43,  44, 
45).  If  that  were  originally  so,  why  have  the  flatfish  an 


EMBRYOGENY  209 

embryogeny  which  strives  from  the  beginning  towards 
this  peculiarity  ?  Why  are  the  eyes,  as  with  normal 
fishes,  always  singly  placed  on  both  sides  and  travel 
first  of  all  in  the  young  fish  so  as  to  come  together  ? 

We  have  thus  learned  of  some  cases  in  which  the 
individual  evolutional  history  really  explains  to  us 
how  the  adult  forms  formerly  appeared. 

It  is  scarcely  necessary  for  us  to  emphasize  the 
fact  that  as  regards  the  origin  of  those  types  themselves, 
fish  or  crab  types,  we  learn  nothing  at  all,  but  only 
how  some  fish  and  crabs  can  arrive  at  a  form  deviating 
from  the  normal.  It  may,  however,  be  emphasized 
that  everyone  who  accepts  the  above  conclusion  must 
simultaneously  agree  that  to  each  type  there  belongs 
also  a  particular  process  of  evolution,  otherwise  there 
could  not  be  expected,  from  the  embryogeny,  any 
explanation  of  the  systematic  classification. 

(b)  Of  somewhat  wider  application  are  the  conse- 
quences of  the  conclusions  which  have  been  drawn  from 
observation  of  other  dissimilar  peculiarities  of  the 
embryogeny  of  many  recent  animals.  The  Salamander 
(Salamandra  maculosa)  is  viviparous  and  produces  its 
larvse  in  the  water.  The  larvae  possess  in  conformity 
therewith  gills  for  breathing  water  and  a  rudder 
tail  for  swimming.  A  quite  near  relative,  the  black 
Alpine  Salamander  (S.  atra),  also  viviparous,  bears 
only  two  to  three  young,  which  are  born  on  land ;  the 
young  are  conformably  provided  with  lungs  for  breathing 
air  and  with  a  round  tail  for  creeping.  But  these 
young  ones  pass  through,  in  the  mother's  body,  a 


210  THE  THEOBY  OF  EVOLUTION 

stage  with  well-formed  gills   and  a  rudder  tail,  which 
naturally  are  never  of  service. 

What  follows  from  these  examples,  and  what  has  been 
inferred  ?  Other  newts,  like  the  Tritons,  lay  their  eggs 
in  water,  from  which  then  in  the  first  place  there  issues 
a  larva  developed  with  swimming  tail  and  gills  and  later 
the  form  adapted  for  land  life  of  the  lizard  with  lungs 
and  round  tail.  The  two  Salamanders  above  mentioned 


4^\N 
/  • 


FlG.    45; — TURBOT; 

produce  first  the  larvse,  the  one  kind  earlier,  the  other 
later. 

This  therefore  implies  that  to  the  type  of  the  tailed 
newt,  specially  to  the  sub -order  of  the  Salamandrinee, 
a  larval  form  belongs,  which  lives  in  the  water  and 
is  conformably  equipped,  but  that  the  development, 
which  with  all  is  the  same  and  remains  the  same,  may 
be  more  or  less  intra-uterine.  Why  that  happens  we 
need  not  really  know ;  for  the  Alpine  Salamander, 
which  lives  in  damp  woods  of  high  elevation,  the  neces- 


EMBRYOGENY  211 

sity  or  also  the  possibility  of  bringing  forth  the  young 
in  water  in  any  case  ceased  to  exist.  That  in  the  first 
place  did  not  alter  its  embryogeny  at  all,  and  conse- 
quently it  still  produces  the  larval  form  which  now 
appertains  to  its  type.  Experiments  have  also  been 
successful,  which  is  not  to  be  wondered  at,  in  causing 
it  also  to  produce  its  young  in  the  water,  provided  with 
gills  and  a  rudder  tail. 

Such  vacillations  between  inner  and  outer  (free) 
embryonic  development  are  very  often  met  with. 
The  c  smooth  shark  of  Aristoteles '  (Mustelus  Icevis) 
is  viviparous  in  contradistinction  to  all  other  Sharks. 
There  are  oviparous  and  viviparous  insects  and  also 
lizards.1 

With  regard  to  the  viviparous  Hill  Lizard  (Lacerta 
vivipara)  Kammerer  states  :  c  it  is  normally  viviparous  ; 
the  young,  from  three  to  ten  in  number,  are,  it  is  true, 
often  at  the  moment  of  birth  still  enclosed  in  the  egg 
skin,  which,  however,  in  a  few  minutes  or  hours  they 
burst  open.  If,  however,  the  parent  animals  are 
kept  in  an  unaccustomed  warm  temperature  of  at 
least  25°C.,  then  they  lay  eggs,  whence  the  young  cannot 
so  quickly  escape  ;  at  the  first  egg-laying  period  in 
high  temperature  the  time  between  laying  and  hatching 
out  is  from  three  to  nine  days,  the  eggs  are  no  more 
numerous  than  before  and  have  no  shell;3  .  .  .  the 

1  The  following  details  are  taken  from  Vererbung  Kiinstlichen  Zeugungs- 
und  Farbenveranderungen  of  Dr.  P.  Kammerer  in  the  Umschau,  1911,  No.  7. 

2  In  consequence  of  the  heat  the  Lizards  are  also  of  a  darker  colour, 
which  is  recognizable  already  in  the  embryo  still  inside  the  egg. 

P2 


212 


THE  THEORY  OF  EVOLUTION 


second  laying  period  yields  us,  however,  five  to  twelve 
eggs,  which  are  enveloped  in  a  parchment- like,  yellowish- 
white,  opaque  shell,  like  those  which  other  Lizards 
possess/  l 

With  the  Meadow  Lizard  (L.  serapa)  Kammerer  has 

established  the  fact  that  the 
normally  parchment-like  eggs 
become  quite  hard-shelled  (and 
at  the  same  time  round)  if  the 
parents  are  kept  permanently 
under  a  temperature  of  30°  to 
35°  C.  (Fig.  46).  If  the  lizards 
be  restored  to  the  normal 
cooler  conditions,  the  first 
generation  lays  still  hard- 
shelled  eggs  ;  and  also  the 
young  which  are  born  under 
normal  conditions  from  the 
c  heat  forms/  which  have  be- 
come black  by  reason  of  the 
warmth,  still  clearly  show  the 
black  coloration  in  the  first 
generations  and,  quite  natur- 
ally, the  more  so  the  nearer 
they  approach  the  adult  form.  The  very  first  stages 
show  still  clearly  the  lighter  colouring. 

This  example  confirms  in  all  points  what  we  have 
so  far  said  regarding  the  influence  of  the  external  world 
and  the  influencing  of  the  embryonic  stages  ;  it  shows 

1  '  Other  '  =  normal  egg-laying  forms. 


c  d 

FIG.  46.  —  THERMAL    CHANGES 

IN  THE  MEADOW  LIZARD. 
a,  normal  animal ;  b,  artificially 
blackened;  c,  normal  egg;  d, 
egg  of  first  deposit  in  heat ;  e, 
hard-shelled  egg  ex  second  and 
third  laying  periods. 

(After  Kammerer.} 


EMBRYOGENY  213 

also  that  there  are  many  vacillations  in  the  relations 
of  the  intra-  to  the  extra-uterine  period  of  development. 

In  the  Alpine  Salamanders  we  observe  how  an 
internal  stage  can  be  omitted ;  in  the  Mountain  Lizard 
the  contrary  can  be  effected  by  experiment. 

(c)  We  will  now  assume  that  the  causes  which  have 
led  to  the  said  change  in  the  Alpine  Salamander  con- 
tinued, and  also  increased  in  power,  so  that  the  inutility 
of  a  constructed  gill  stage  became  ever  greater.  We 
know  that  in  such  cases  a  tendency  immediately  shows 
itself — and  this  is  the  case  with  all  organisms — no  longer 
to  form  such  non-functional  organs.  The  result  will 
be  that  at  first  a  defective  construction  follows,  until 
finally  the  former  organ  perhaps  entirely  disappears, 
or  it  may  be  used  in  quite  another  form.  The  germ 
development  leads  ever  more  directly  to  the  new  form, 
since  the  previous  one,  under  the  altered  circumstances, 
is  no  longer  suited  to  its  purpose. 

The  gill  branchse  of  the  larval  Alpine  Salamander 
could  consequently  quite  well  be  so  far  reduced  finally 
that  only  splits  or  folds  would  be  formed  in  the  gullet 
as,  with  the  other  Salamander  larvae  and  gill-breathing 
animals,  precede  the  formation  of  the  gills  as  preparatory 
stages.  Then  we  should  have  a  rudiment  in  the  sense 
of  a  formation  which,  by  its  construction  and  position 
in  the  organism,  has  a  similarity  to  definite  organs  of 
other  animals,  but  so  imperfectly  developed,  or  even 
only  suggested,  that  they  can  no  longer  exercise  a  func- 
tion, or  at  any  rate  only  extremely  imperfectly.  That 
would  be  specially  a  rudiment  of  an  evolutionary  stage. 


214  THE  THEORY  OF  EVOLUTION 

The  entire  significance  of  the  rudimentary  gill  in 
this  case  would  obviously  consist  therein  that  the  Alpine 
Salamander  had  become  incapable  of  depositing  its 
young  in  water,  as  it  formerly  did.  It  remained, 
however,  despite  this  change,  in  every  respect  a  true 
Salamander  in  habit  and  also  in  the  embryogeny,  in 
which  only  that  was  altered  which  could  no  longer  serve. 

Regarding  the  origin  of  the  Salamander,  as  member 
of  the  Amphibia  or  Salamander  type,  the  rudiment 
says  absolutely  nothing ;  its  explanation  as  rudiment  pre- 
supposes rather  the  existence  of  the  Alpine  Salamander. 

(d)  Rudiments  now  play  an  important  role  in  the 
theory  of  evolution,  but  mostly  a  very  inglorious  one. 
Conscientious  research  must,  however,  in  the  first  place 
ascertain  whether  a  rudiment  really  exists  before 
conclusions  are  come  to.  Wherever  an  actual  function 
can  be  determined,  or  some  formation  under  consider- 
ation cannot  generally  be  regarded  as  an  organ,  but, 
for  instance,  only  as  a  necessary  preliminary  for  the 
fashioning  of  the  adult  form,  then  there  is  no  question 
of  a  rudiment.  In  the  first  case  the  actual  function 
fulfilled  explains  entirely  the  existence  of  that  organ, 
and  no  ground  longer  exists  for  seeking  for  another 
earlier  function,  which  the  presence  of  that  formation 
should  render  comprehensible.1 

In  the  second  case  it  is  precisely  so.     The  organs 

1  For  a  long  period  it  was  the  fashion  to  designate  all  formations, 
whose  function  was  unknown,  straightway  as  rudiments.  Ill  this  way 
Wiedersheim  has  made  a  large  collection  of  rudiments  in  man.  See,  for 
instance,  E.  Wasmann  :  Biologie,  etc.,  p.  454,  and  Kampf  urn  das  Entwickl- 
ungsproblem,  p.  94. 


EMBRYOGENY 


215 


arise  in  the  embryo  not  all  at  once  ;  they  are  gradually 
constructed.  A  stage,  therefore,  which  can  be  recog- 
nized as  such  a  beginning  from  its  actual  subsequent 
fate,  has  absolutely  nothing  to  do  with  a  rudiment.1 

Examples  of  actual  retrogression  are  not  rare. 
In  some  whales  (e.g.  Ealcena  mysticetus — Greenland 
Whale)  there  are  found  entirely  buried  in  the  flesh 
some  remains  of  the  pelvis  and  the  upper  and  under 
thigh-bone,  both  imperfectly  formed.  Externally,  of 


FIG.  47. — BALJENA  MYSTICETUS  (Greenland  Whale).     (After  Heffe.) 

hinder  extremities  there  is  nothing  now  perceptible 
(Fig.  47). 

It  is  clear  that  these  bones  form  no  longer  a  function- 
ally capable  leg.  We  assume,  therefore,  in  order  in  any 
case  to  have  a  reason  for  their  existence,  that  they  are 
rudiments  (remains)  of  formerly  normally  constructed 
extremities  which  have  become  superfluous  owing  to 
the  adaptation  of  the  animal  to  life  in  the  water  and 
which  appear  destined  to  disappear  entirely.  In  other 
species  of  whales  there  is  no  longer  a  trace. 

The    Seals   (Sea    Lions)   show   also  a   rudimentary 

1  A  renowned  '  rudiment '  of  this  kind  we  hear  of  in  the  gill  slits  of 
mammals  and  man. 


216  THE  THEORY  OF  EVOLUTION 

condition  of  the  hinder  limbs,  but  in  some  forms  they 
can  still  be  used  (by  pushing)  for  locomotion.1  Rudi- 
ments are  also  those  temporary  teeth  which  appear  to 
fulfil  no  function,  which  we  note  in  young  whales,  in 
bird  embryos  or  young  birds  ;  also  the  temporary  and 
defectively  formed  wing  stage  of  the  Termitoxenia,  a 
termitophil  fly  (see  p.  201). 

Conclusion  from  (1). 

The  actual  points  deduced  from  the  facts  of  embryo- 
geny  all  lead  to  the  conclusion  :  That  we  obtain  manifold 
information  regarding  the  former  conditions  of  organisms 
but  none  at  all  regarding  the  origin  of  the  types  to 
which  they  belong. 

If  the  nauplius  stage  of  the  Lepas  species  really  shows 
anything,  that  arises  because  there  is  ascribed  to  the 
type  of  the  lower  Crabs  also  a  typical  embryonic 
development.  The  Lepas  were  therefore  formerly  free- 
living  Cirripedia,  which  is  seen  by  the  still  unaltered 
remainder  of  the  ontogeny  and  the  still  recognizable 
crab  characters  of  the  adult  form. 

The  Sole  was  really  a  fish  when  it  assumed  the  prone 
mode  of  life,  the  Termitoxenia  a  fly  when  it  became 
a  termite  guest,  the  Whale  a  pure  mammal  when  it 
'  went  into  the  water/  etc. 

How  Flies,  Soles,  Crabs,  Mammals  have  phylogene- 
tically  arisen  none  of  the  examples  show  us. 

1  The  front  extremities  are  changed  into  rudders  (fins)  in  Whales  and 
Seals,  but  the  internal  skeleton  is  still  fairly  that  of  the  quadrupedal 
Mammalia.  They  show  thus  still  more  of  a  positive  adaptation. 


EMBRYOGENY 


217 


(2)  The     speculative     utilization     of     enibryological 
evidence. 

Speculation  has  not  been  satisfied  therewith.  Each 
'  rudiment '  which  is  met  with  in  the  embryogeny  of 
a  present  organic  form  should  become  a  document  of 
the  actual  historical  evolution  of  the  type  itself,  at 
least  in  such  cases  where  the  rudiment  concerned 
possesses  a  similarity  to  a  really  functional  organ  of  an 
adult  type,  even  though  a  very  distant  one.  A  c  germ 
rudiment '  of  a  mammal  embryo  should  no  longer 
point  to  a  former  free-living  larval  stage  of  the  mammal 
but  to  a  true  adult  fish  or  a  true  tadpole.  That  is 
maintained  and  believed.1 

The  most  definite  and  most  general  formularization 
of  the  enibryological  argument  is  given  by  Hackel  in 
his  '  biogenetic  fundamental  law/ 

In  the  best-known  form  it  runs  thus  :  ~  '  The  onto- 
genesis, or  the  development  of  the  individual,  is  a  short 
recapitulation,  controlled  by  the  laws  of  inheritance 
and  adaptation,  of  the  phylogenesis  of  the  ancestors 
which  form  the  pedigree  of  the  individual  concerned/ 

1  It  will  perhaps  be  said  that  '  true '  is  arbitrarily  used ;   '  fish-like  ' 
was  only  intended.     To  that  it  may  be  replied  that  the  argument,  in  the 
form  in  which  we  have   presented  it,  is  at  least  used  by  the  Hackelites. 
It  should  be  really  applied  to  lower  classes— for  instance,  Reptiles  or  Fish. 
If  the  hypothetical  fish-like  ancestors  of  the  Mammals  were  no  fishes  and 
yet '  true,'  then  this  application  does  not  hold  good.     Furthermore  Hackel 
himself  speaks  quite  simply  of  '  ancestors '  which  may  be  ascertained  by 
his  '  basal  principle.'     The  acceptance,  however,  of  '  fish-like  '  ancestors 
is  not  borne  out  by  actual  observation  of  facts,  but  in  the  meantime  is 
only  based  on  a  fish-like  stage  in  the  Mammalia  already  existent. 

2  Natiirliche  Schopfungsgeschichte,  p.  276. 


218 


THE  THEOKY  OF  EVOLUTION 


In  the  ideal  case  it  would  therefore  suffice  to  care- 
fully observe  the  succession  of  all  germinal  stages  in 
order  perfectly  to  know  the  desired  pedigree.  That 
certainly  scarcely  ever  happens,  since,  according  to 
Hackel  himself,  (  mostly,  in  the  ontogenetic  succession, 
much  is  missing  and  has  become  lost,  that  formerly 
existed  and  really  lived  in  the  phylogenetic  chain  of 
evolution/  '  We  are,  therefore,  in  most  cases,  not  in  a 
position  to  determine  all  the  varied  form  conditions 
which  the  ancestors  of  each  organism  have  passed 
through  separately  by  direct  ontogeny,  but  are 
hindered  as  a  rule  by  many  kinds  of  gaps/ 

The  influence  of  those  causes  which  led  to  the  extinc- 
tion or  the  '  falsification  '  (Falschung)  of  some  stages 
Hackel  calls  '  Ksenogenesis/  The  mode  of  expression 
is  not  badly  chosen  ;  the  principle  is  easily  read  ;  the 
addition,  '  controlled  by  the  laws  of  inheritance  and 
adaptation/  calms  the  reader,  because  it  permits  it  to 
be  supposed  that  Hackel  will  know  the  foundation  for 
his  law.  The  '  Ksenogenesis  '  shows  clearly  that  the 
application  is  not  always  easy :  we  have  to  deal  with 
complicated  cases. 

Despite  this  there  is  lacking  in  the  Hackel  funda- 
mental principle  absolutely  all  that  must  be  demanded 
for  a  scientific  principle  for  the  elucidation  of  the  actual 
genetic  history  of  an  organic  group.  In  the  first  place 
it  is  purely  an  a  priori  assumption  and  not  one  based 
on  observed  facts.  It  leads,  in  the  second  place,  logically 
followed  out,  to  actually  impossible  consequences  and 
misunderstands  entirely  the  essence  of  the  embryonic 


EMBRYOGENY 


219 


evolution ;  and  finally,  it  has  come  not  only  to  no 
conclusion  with  the  palaeontologists,  but  has  led  them 
towards  assumptions  which  the  facts  directly  contradict. 

(a)  The  '  biogenetic  fundamental  principle '  is  a 
mere  assumption  which  asserts  that  which  is  to  be 
proved,  and  does  so  in  contradiction  to  everything 
that  the  actual  observations  permit  of  assuming. 

Hackel  says  himself  that  in  the  embryogeny 
1  mostly '  much  is  lacking.  We  can,  however,  only 
know  whether  something  is  lacking  and  what  it  is 
if,  on  the  other  hand,  it  is  clearly  established  what 
should  be  there.  That  which  should  be  present  Hackel 
must  thus  have  seen  in  some  other  quarter,  and  not 
in  the  embryogeny  itself  ;  otherwise  we  should  have 
had  a  quite  indisputable  circle  of  conclusions. 

The  origin  of  the  organisms — and  this  by  a  quite 
definite  chain  of  ancestry — is  therefore  assumed  here. 
But  whence  ?  We  have  given  above  some  of  the  best 
known  examples  which  told  us  something  regarding 
the  life  of  the  predecessors  and  their  appearance  ; 
they  all,  however,  without  exception,  show  only  what 
an  organism  had  to  contend  with  when  it  was  already 
a  member  of  a  well-defined  type — for  instance  a  fish, 
a  crab,  a  mammal,  an  amphibian,  etc.  Of  the  origin 
of  the  Crabs,  Fishes,  Mammals,  etc.,  we  learnt  nothing 
at  all.  Thereby  for  instance  there  might  be  deduced 
from  a  rudimentary  gill  stage  a  mammal  or  a  formerly 
free-swimming  larva  of  a  mammal,  but  not  that  there 
were  formerly  no  mammals,  but  only  fish. 

Thus,  from  the  actual  observations  of  the  alteration 


220  THE   THEOKY   OF  EVOLUTION 

in  the  embryogeny  of  many  organisms,  Hackel 
does  not  know  that  the  Mammals  were  once  fish  or 
tadpoles  ;  in  them,  therefore,  he  has  no  c  norm  '  for 
what  is  ( lacking  '  or  '  falsified/  l 

(b)  The  logical  extension  of  the  principle  leads 
to  quite  untenable  consequences,  or  it  proves,  if  these 
consequences  be  avoided,  nothing  more  regarding  the 
origin  of  the  types  (Birds  and  Mammals  for  instance). 

A  simple  consideration  will  convince  us  of  this. 
In  the  individual  genesis  of  a  present-day  bird  there 
arises,  as  experience  shows,  a  hard-shell  egg  stage  which 
is  usually  termed  a  c  bird's  egg/  This  bird's  egg  is  not 
to  be  confounded  with  the  actual  female  germ  cell 
which  scientifically  is  generally  termed  egg  (or  egg 
cell).  The  germ  cell  is  originally  a  microscopically 
small  cell  which  quite  early  accumulates  in  the  proto- 
plasm yolk  particles  for  the  nourishment  of  the  future 
embryo  and  thus  forms  the  '  yolk/  This  yolk  is  the 
fertilizable  female  sexual  cell ;  only  after  fertilization, 
when  traversing  the  oviduct,  are  further  coatings  added 
— the  material  for  which  is  supplied  by  glands — viz. 
the  albumen  (white  of  egg),  then  a  fine  double  egg  skin 
(directly  under  the  lime  shell  and  detachable),  and 
finally  the  hard  lime  shell.  Thus  is  the  egg  finally  '  laid/ 
The  germ  cell  alone,  or  already  in  the  form  of  a  germ 
stage,  is  thus  enclosed  in  the  egg  when  laid.3 

1  That  palaeontology  also  gives  no  '  norm  '  we  shall  soon  see. 

2  An  '  embryo  '   (germlet)  is  then,  strictly  speaking,  already  present  if 
the  single  cell  stage  is  no  longer  there — i.e.  after  the  first '  division  '  (=  divi- 
sion of  the  developing  egg).     Usually  certainly  the  term    '  embryo  '   is 
only  applied  to  more  advanced  stages. 


EMBKYOGENY  221 

According  to  Hackel  we  can  and  must  come  to 
this  conclusion  :  Immediately  upon  the  monocellular 
stage  of  the  bird  parents  there  followed  organisms 
which,  as  hard-shelled  eggs  with  yolk,  albumen,  etc., 
swam  in  the  sea  or  lay  upon  the  sand.  These  ancestors 
were  absolutely  nothing  else  than  such  hard-shelled 
formations.  How  they  acquired  the  yolk,  albumen, 
and  the  lime  shell,  and  how  they  generally  worked  their 
way  out  and,  later  on,  swam  as  fish  in  the  sea — since  later 
they  were  fish,  as  the  gill  rudiment  of  the  bird  embryo 
should  prove — that  is  a  very  difficult  question  to  answer.1 

It  is  certain  that  no  Hackelian  draws  this  conclusion. 
He  would  rather  refer  to  the  saving  clause  that  the 
'  laws  of  inheritance  [?]  and  adaptation '  required 
many  things— in  short,  that  the  krenogenesis  must 
not  be  left  out  of  account. 

Very  probably  it  would  be  said  that  the  hard-shelled 
egg  stage  which,  precisely  according  to  HaekeFs 
disciples,  was  certainly  not  always  there  but  has  arisen, 
may  be  an  adaptation  in  the  embryogeny  itself.  To  the 
further  question — In  ivhich  embryogeny? — every  one 
would  involuntarily  reply :  In  that  of  the  bird.  Any- 
thing else  cannot  wisely  be  put  forward,  and  the  sense  of 
the  reply  is  simply  this :  an  actual  bird  has,  in  its  em- 
bryogeny, adopted  this  adaptation,  since  it  no  longer, 

1  A  particularly  logical  Hackelian  could  certainly  say  with  perfect 
right  that  it  is  true  that  as  a  rule  '  much '  was  altered  and  '  falsified,' 
but  not  the  lime-shell  stage,  according  to  his  conviction,  since  a  '  norm,' 
which  could  decide  the  question,  is  not  given.  The  '  laws  of  inheritance 
and  adaptation '  also  apply  and  would  do  so  precisely  if,  generally  speaking, 
no  development  of  the  types  had  taken  place. 


222  THE  THEORY  OF  EVOLUTION 

as  formerly,  laid  its  eggs  in  the  water,  but  transferred 
the  development  of  the  germ  to  its  interior.  Since 
the  albumen,  the  egg  skin,  the  lime  shell  are  all  deposited 
by  glands  and  these  are  situated  in  the  oviduct,  in 
the  oviduct  alone  could  these  glands  be  arranged  as 
an  absolutely  necessary  condition  for  the  formation 
of  the  covers  and  therewith  the  newly  adapted  form 
of  development  of  the  germlets  (Keimlinge).  The 
formation  of  the  glands  is  furthermore  in  that  case 
only  a  purposely  adapted  means  for  the  new  embryogeny 
when  the  egg  had  been  previously  fertilized  in  the 
uterus  or  oviduct.  There  were  consequently,  at  the 
time  when  that  adaptation  occurred,  males  and  females, 
and  the  seminal  cells  were  introduced  by  pairing  into 
the  genital  apparatus  of  the  female.  In  brief,  the 
birds  were  at  the  time  of  that  hypothetical  adaptation 
the  same  as  now.  They  had,  however,  teeth  in  the 
beaks  and  also  perhaps  (all  ?)  a  longer  tail :  there 
are  some  points  of  support  for  this  in  palaeontology 
and  embryogeny. 

Among  the  Mammals  we  arrive  at  similar  stages 
which,  according  to  their  entire  nature,  must  be  ac- 
cepted only  as  adaptations  of  the  embryonic  life  itself— 
and  that  in  the  uterus  of  a  mammal,  unless  it  be  assumed 
that  the  ancestors  of  the  Mammals  formerly  lived  as 
grown-up  individuals  in  the  interior  of  the  maternal 
body.  What,  then,  were  these  mothers  ? 

In  short — for  the  case  that  in  a  general  way  the 
embryogeny  of  the  Mammals  and  Birds  was  not  always 
the  same  as  to-day — the  development  of  the  germ  of 


EMBKYOGENY 


223 


the  present  Mammals  or  Birds  shows  everywhere  adap- 
tations which  have  been  brought  about  by  the  Mammals 
and  Birds.  With  regard  to  the  evolution  of  the  type 
6  Mammal '  or  (  Bird  '  we  learn  nothing. 

(c)  The  embryogeny  of  the  Mammalia  is  precisely 
as  different  from  the  embryogeny  of  the  Fishes  as  a 
completely  formed  mammal  is  from  a  complete  fish. 
Just,  therefore,  as  a  complete  mammal  form  can  under 
no  circumstances  be  connected  with  an  adult  and 
completed  fish,  just  so  can  no  single  stage  of  germ 
development  (not  even  in  the  so-called  germ  stage) 
of  the  Mammals  be  connected  with  an  embryonic 
stage  of  the  Fishes. 

That  is  a  result  at  which  0.  Hertwig  has  arrived 
after  many  years  of  zealous  research,  and  which  Naegeli 
has  already  expressed  in  the  renowned  sentence :  '  In 
the  egg  of  the  hen  the  species  is  just  as  perfectly  main- 
tained as  in  the  hen,  and  the  hen's  egg  is  just  as  widely 
different  from  the  frog's  egg  as  the  hen  from  the  frog. 
If  this  appears  otherwise  to  us  this  is  only  because 
in  the  hen  and  the  frog  many  distinguishing  characters 
are  obvious,  while  the  distinguishing  qualities  in  the 
eggs  lie  hidden  therein.  If  the  hen's  egg  did  not  contain 
the  entire  essence  of  the  species,  a  fowl  could  not  always 
arise  from  it  with  the  same  certainty/  1 

The  first  part  of  this  citation  is  also  found  in 
Korschelt  and  Herder's 3  well-known  textbook  expressed 

1  C.  von  Naegeli :  Mechanisch-physiologische  Theorie  der  Abstammungs- 
lehre,  p.  22. 

2  Lehrbuch    der    vergleichenden    Entwicklungsgeschichte  der  wirbellosen 
Tiere,  part  I,  p.  136. 


224  THE  THEORY  OF  EVOLUTION 

approvingly  and  with  a  detailed  confirmation  by 
0.  Hertwig.1  '  From  the  fact  that  the  ontogenesis  of 
the  plant  and  animal  species  usually  begins  with  a 
simple  cell  stage,  the  fertilized  egg,  it  has  been  con- 
cluded that  all  organisms  have  descended  from  common 
unicellular  indifferent  ancestors  :  the  hypothesis  of 
a  monophyletic  pedigree  has  been  put  forward.  How 
improbable,  however,  must  this  appear  to  us  if  we 
start  from  the  point  of  view  above  set  forth  —  that  ac- 
cording to  the  ontogenetic  causal  law  the  fertilized 
egg  cells  of  the  different  species  of  animal  vary  in 
their  being  quite  as  much  from  each  other  and  are 
quite  as  good  bearers  of  the  various  specific  differences 
as  are,  at  the  end  of  their  ontogenesis,  the  perfected 
individuals  upon  whose  characters  we  base  our  animal 
system/ 

The  same  considerations  suggest  themselves  when 
it  is  sought  to  be  concluded,  by  reason  of  the  '  similarity  ' 
of  many  embryonic  stages  of  the  Mammals  to  tho&e 
of  adult  fishes  or  the  larvae  of  Amphibia,  '  that  the 
Mammals  descend  from  Amphibia  or  Fishes/  2  '  The 
recapitulation  theory  in  the  old  sense  '  cannot  therefore 
*  be  longer  maintained/  3 

Hacked  basal  principle  therefore  involves  a  perfect 
miscomprehension  of  the  nature  of  embryogeny.  The 
life  of  a  mammal  begins  with  an  egg  which  a  parent 
animal  of  the  same  species  has  formed  as  an  extract 


1  AUgemeine  Biologie,  p.  674. 

2  Ibid.  p.  675. 


Ibid. 


EMBRYOGENY 


225 


of  its  entire  essence.  The  parent  animal  produces,  how- 
ever, no  amoeba  but  reproduces  its  own  form.  Each 
germ  stage  is  through  and  through  a  mammal  in  the 
making,  devoted  to  that  one  object  by  the  preceding 
stage  and  itself  determining  the  succeeding  one  to  the 
same  end.1  The  types  have  thus  experienced  no 
greater  alteration  in  their  embryogeny  than  in  their 
grown  condition,  which  in  all  cases  is  only  the  result  of 
germ  stages  determined  in  one  particular  direction. 
Since,  however,  the  types  to  the  eye — whether  accord- 
ing to  present  systematic  classification  or  according 
to  palaeontological  finds — as  adult  mammals  never 
show  any  association  with  any  other  class  whatever, 
therefore  also  the  embryonic  stages  can  present  no 
approximation  since  they  belong  to  the  complete 
condition  and  produce  it. 

(d)  As  regards  the  applicability  of  the  '  biogenetic 
basal  principle '  in  palaeontology  Zittel  stated  in 
1895  at  the  International  Geological  Congress :  '  If 
palaeontology  be  consulted,  it  must  be  recognized  that 
this  hypothesis  has  not  been  confirmed  in  any  way/ 
He  then  shows  by  several  examples  at  what  '  peculiar 
ancestors '  we  must  arrive  according  to  the  '  basal 
principle ' — for  instance,  for  the  Crinoids  (Hairstars) 
and  Sea  Urchins,  which,  however,  '  would  not  accord 
in  the  remotest  degree  with  the  facts/  Such  examples 

i  All  this  has  been  determined  by  modern  biologists  by  observation 
and  experiment.  See,  for  instance,  Driesch  :  Philosophic  des  Organischen, 
I,  p.  76;  Analytische  Theorie  der  Formbildung,  Korschelt  and  Herder, 
part  I,  p.  81 ;  Das  Determinationsproblem ;  O.  Hertwig :  Allgemeine 
Biologic,  p.  572, '  Die  Theorie  der  Biogenesis' 

Q 


226  THE  THEOKY  OF  EVOLUTION 

showed  the  '  futility  of  the  conclusions  '  which  are  due 
to  the  embryological  methods.1  '  The  examples  might 
easily  be  multiplied  tenfold/ 

According  to  Deperet '  this  law  requires  to  be  applied 
every  time  with  the  most  extreme  care.  It  would 
in  no  case  be  able  to  dispense  with  the  subsequent 
proof  which  is  provided  by  the  actual  evolutionary 
history,  i.e.  by  the  knowledge  of  the  palseontological 
records/  3 

That,  in  ordinary  language,  means  that  it  might 
by  chance  so  happen,  as  Hackers  once  '  fundamental 
law  '  demands,  but  ordinarily  it  is  otherwise,  and  in  that 
case  the  investigator  adheres  to  the  other  cases.  If, 
despite  this,  the  said  investigators  grant  that  earlier 
forms  in  the  adult  condition  were  permanently  so 
constituted,  as  their  present  successors  are  only  tem- 
porarily constituted  in  their  '  embryonic  3  or,  better, 
'  young  '  stages,  that  is  by  no  means  surprising. 

'  The  palseontological  Belinuridse' — says,  for  instance, 
Zittel  in  his  exposition — '  resemble  a  thousand  young 
larvae  of  the  living  (recent)  "  Swordtail "  (Limulus)  ; 
the  Pentacrinus,  larvae  of  the  Antedon,  stands  closer 
to  many  fossil  Sea  Lilies  than  does  the  adult  animal. 
Certain  fossil  Sea  Urchins  retain  permanently  the  young 
characters  ...  of  their  still  living  relatives.  The 
splendid  investigations  of  Hyatt,  Wiirtenberger,  and 
Branco,  have  shown  that  all  Ammonites  and  Ceratites 
(Cephalopods  to  which  the  Cuttle  Fish  belong)  pass 

1  Deperet :    Umbildung  der  Tierwelt,  p.  107. 
i  Ibid.  p.  40. 


EMBKYOGENY  227 

through  a  Goniatite  stage  and  that  frequently  the 
internal  convolutions  of  an  Ammonite  in  their  form, 
ornamentation,  and  lines  of  suture  *  resemble  any  other 
earlier  existing  genus  in  the  adult  condition/  2  That 
is  quite  natural. 

It  is  quite  natural,  since  each  alteration,  whether 
retrogressive  or  progressive,  influences  the  entire  indi- 
vidual. If,  for  instance,  a  Sea  Lily  assumed  another 
form — either  by  specialization  or  in  a  definite  direction 
as  adaptation  to  a  definite  mode  of  life — it  would  there- 
fore only  reject  the  hitherto  embryonic  development 
in  so  far  as  the  new  complete  form  to  be  created  rendered 
necessary.  The  new  constructions  would  be  simply 
added  to  the  former  constructive  process,  and  so  it 
has  remained  until  the  present.  The  newly  acquired 
is  always  the  last  in  the  ontogenesis,  the  old  becomes 
always  the  younger  or  more  embryonic.  All  cases 
brought  forward  and  really  observed  thus  only  show 
how  little  since  the  Palaeozoic  period  the  types  like 
the  Sea  Urchin,  Sea  Lily  (Crinoids),  etc.,  have  changed. 
The  entire  transformation  indeed  is  confined,  for 
example,  in  the  Belinuridse  mentioned,  to  those  few 
alterations  which  in  the  evolutionary  course  of  the  recent 
Limulus  follow  upon  the  Belinuridse  stage,  precisely 
as  in  the  case  of  a  retrogressive  transformation — for 

1  The  long  since  extinct  Ammonites  (Ammonhorns)  were  shell-dwelling 
Cephalopoda  which  in  certain  interspaces  sometimes  constructed  a  new 
dwelling  chamber  in  the  earlier  ones  ;  the  line  of  separation  between  each 
two  chambers  is  called  the  suture  line  (division  seam).      This  forms  one 
of  the  discriminating  specific  characters  and  was    subject  to  constant 
modifications. 

2  Deperet :   Umbildung  der  TierweU,  p.  107. 

Q2 


228  THE  THEORY  OF  EVOLUTION 

example,  as  the  result  of  parasitism — the  entire  altera- 
tion shows  itself  between  the  first  abnormal  germ 
stage  and  the  completed  form. 


§  4.  Summary  of  the  collected  results. 

(1)  We  have  seen  how  manifold  are  the  alterations 
to-day    which    underlie    animals    and    plants.     Direct 
influences  (stimuli)  by  climate,  constitution  of  soil,  etc., 
isolation  and  close  interbreeding  through  long  periods, 
adaptation  to  quite  special  modes  of  life  such  as  Parasites 
or  Symbionts — all  these  effect  changes  in  a  progressive 
or  retrogressive  sense,  i.e.  in  the  shape  of  new  formations 
and  more  marked  differentiation  or  of  regression  of 
existing  features. 

(2)  None  of  the  transformations  observed  or  easily 
to  be  regarded  as  such  ever  go  so  far  that  the  allocation 
to  a  certain  type  can  no  longer  be  made  with  certainty, 
whether  in   the   completed   adult  condition  or  in   the 
embryogeny,  which  indeed  likewise  forms  a  constituent 
of  the  typical  distinguishing  character.     There  arise, 
it  is  true,  new  species,  genera,  and  even  families,  but 
no  animals  and  plants  with  an  entirely  deviating  plan 
of  construction  and  higher  total  organization.     With 
the  Parasites  there  remains  at  least  a  portion  of  the 
embryogeny  unchanged. 

(3)  The  alterations  which  we  can  determine  in  fossil 
organisms  are  of  the  same  kind  as  the  present  ones — 
i.e.  they  also  carry  in  themselves  the    distinguishing 
characters  either  of  a  direct  adaptation  to  the  environ- 


Polyphaga 


/Lamellicorn. 
Rhynchophora 
Phytophaga 

Heteromera 

Teredilia 

Sternoxia 
Serricorn. 
Macrodact. 

Brachymer. 
Clavicornia 

Malacoderm 
Palpicornia 

Staphylini- 
\     formia 

Adcphaffa 

Scarabacid.       .Hl.^-—  —  —  1  .    \ 

\ 

\ 

\ 

\\\ 

FIG.  48.  —  PEDIGREE  OF  THE  BEETLE  FAMILY  (after  Handlirsch). 

Passalidae          

Tpiflnr                           ...  | 

l 

^ 

**+?\ 

~~,    N  v 

1 

Curculionid.      ••••••••j 
Brenthid 

inthribid                   •     I                   1 

Cerambycid.      ••• 

>—— 

_'"___. 

Tenebrionid.      B_H_H 

> 

-  -^-1^> 

Lagm  ac 

Othniidae           

Monommid.        

Pj/rnrfiroiflrtf      .    .... 

^, 

-.v-- 

~  ^^  ^ 

—  —  - 

——  - 

Kwcnfinidfte       ,    

Elateridae         ^^^ 

•_M_Wi_HMM 

-- 

Rliipicerifl, 

DasciUid 

, 

?  Heterocerid.    
t  Qeorysaidae     

J 

jiyrrniaae 



\ 

,f<r><>f>iinf>n.irl,          _______ 

---"-V 

XV. 

f!li/1.nm.yt>hi.d. 

r1   /  rrl  "clnp 

Adimeridae        

rv" 

Lathridiid          ••  •  

-«. 

Thorictidae       

"- 

— 

C  ryptopKagia. 

hrotylidae 

Synteliidae         

_- 

-- 

Derodontidae     

™  • 

* 

Melyridae          

\ 

OOOfM 

N- 

1 

Staphylinidae    •_•_• 
Platypsyllid.     

•_--_. 



.S*x  S»'» 

Cnyi/lnpMdne 



Aphaenocephal.  _____ 
Clambidae          
Leptinidae          



VJ»t<foot 

x  n 

_„,'' 

\ 

Amphisoidae      —  —  ~~ 

*\  [/£/* 

Rhygodidae         _____ 

Dogger  \  J 

§    § 

^       £ 

I 

Cainozoic 

i 

1 

SUMMARY    OF    RESULTS  229 

ment  and  quite  special  objects,  habitats,  or  stations 
(law  of  specialization  and  convergence),  or  to  parasitic 
and  sessile  modes  of  existence  (law  of  regression). 

(4)  This  perfect  agreement  in  the  mode  and  manner 
of  the  transformations  and  their  extent,  as  between 
the  recent  and  the  fossil  organisms,  shows  that  the 
same  causes  which  are  busy  to-day  in  alteration  of 
form  were  so  formerly  and  no  others,  since  otherwise 
the  mode  and  manner  of  the  transformations  could  not 
be  the  same  in  both  cases. 

That,  however,  the  extent  of  the  changes  is  the  same 
now  as  formerly — i.e.  that  they  never  completely  wipe 
out  a  given  type — shows  clearly  that  a  more  thorough- 
going transformation  and  alteration  is  excluded.  That 
which  has  never  happened  can,  according  to  the 
principles  of  natural  science,  also  not  happen. 

The  organic  kingdom  therefore  forms  no  unit  but, 
as  established  by  natural  research,  a  definite  number 
of  true  types,  i.<e.  grades  of  perfection.  Ever  more 
and  more  do  the  investigators  see  that  their  chief  task 
consists  therein,  to  ascertain  the  history  of  the  separate 
groups  of  animals  and  plants  and  to  discover  the  laws 
and  causes  of  their  evolution. 

How  imperfectly  even  this  limited  task  has  so  far 
been  fulfilled  is  shown,  better  than  by  a  detailed  presen- 
tation, by  the  table  given  as  an  example  (Fig.  48)  from 
Handlirsch  l  showing  the  pedigree  of  the  Beetle  family, 
i.e.  of  a  subordinate  systematically  classified  category. 

The  extended  lines  show  actual  discoveries — they 

l  Die  fossilen  Insekten,  p.  1279. 


230  THE  THEORY  OF  EVOLUTION 

run  almost  without  exception  parallel — the  lines  which 
should  connect  the  separate  families  are,  almost  without 
exception,  broken,  i.e.  hypothetical. 


Conclusion. 

The  period  of  '  fantastic  evolutional  histories/  as 
Deperet 1  expresses  it,  or  the  '  methods  of  approximating 
valuation/  is  certainly  disappearing.  For  true  progress 
the  a  priori  hypotheses  of  Darwin  and  others  have  yielded 
not  only  absolutely  nothing,  but  done  much  harm. 
Professor  Steinmann  expresses  himself  in  that  connec- 
tion as  follows — in  which  bitterness  is  evident  since 
the  current  evolutional  hypotheses  have  driven  him 
almost  to  c  despair ' :  '  When  a  scientific  branch  of  such 
predominant  importance  as  the  theory  of  descent  gets 
off  the  proper  track  it  naturally  detrimentally  influences 
all  the  branches  of  knowledge  with  which  it  is  organically 
associated.  So  it  is  also  with  palaeontology  (and  to 
a  certain  extent  also  with  geology),  which,  instead  of 
having  an  independent  basis,  has  become  a  vassal  of 
the  Darwinistic-Hackelistic  theory  of  evolution.  With 
the  low  position  in  which  palaeontology  still  remained 
in  the  years  1860  and  thereabouts,  it  became  at  first 
entirely  taken  in  tow  by  them ;  the  significance  of  the 
formation  of  species  and  subjection  to  the  struggle 
for  existence  of  the  phylogenetic  meaning  of  the  syste- 
matic categories  of  the  unity  of  origin  of  the  smaller  and 

i   Umbildung  der  Tierwelt,  p.  143. 


CONCLUSION  231 

larger  animal  and  plant  divisions  were  brought,  without 
proof,  into  the  area  of  fossil  material.  No  wonder  then 
that  palaeontology  could  not  follow  these  academical 
prescriptions,  and,  when  it  tried  to  do  so,  made  a  fiasco/ l 

The  embryological  methods  of  Hackel  have,  ac- 
cording to  Deperet,3  led  the  whole  of  palaeontological 
research  in  a  wrong  direction.  The  '  naive  '  pedigrees  } 
constructed  according  to  them  '  have  crumbled  just  as 
speedily  as  they  have  arisen  ;  they  cover,  as  with  rotten 
wood,  the  ground  of  the  forest  and  only  render  more 
difficult  the  progress  of  the  future/  3 

All  the  more  is  it  to  be  regretted  that  the  neo- 
Lamarckians  wish  to  endeavour  once  more  to  solve  the 
problem  of  evolution  deductively,  since  they  deduce 
the  common  origin  of  plants,  animals,  and  man  from 
the  entirely  wrong  assumption  of  their  essential  equality. 
Despite  all  protests  there  is  thereby  substituted  another 
'  dogma  '  in  the  place  of  the  Darwinian  '  dogma  '  as 
they  express  it.  The  tone  of  their  writings  is  also  not 
always  a  high-class  one.  The  investigators  who  believe 
in  God  are  contumeliously  pitied  :  thus  A.  Wagner 4 
says  of  Wigand  that  his  'in  many  respects  excellent 
adverse  critique  of  Darwinism,  he  has  spoilt,  particu- 
larly, through  the  marked  theistic  colouring  of  his 
philosophy.  Like  Wigand,  too,  did  K.  E.  v.  Baer  spoil 
the  influence  of  his  arguments  by  deriving  from  his 

1  G.  Steinmann :    Die  geologischen  Grundlagen  der  Abstammungslehre, 
p.  17. 

2  Umbildung  der  Tierwelt,  p.  113. 

3  Ibid.  p.  108. 

4*  Oeschichte  des  Lamarckismus,  p.  60. 


232  THE  THEOKY  OF  EVOLUTION 

view  of  the  world  a  theistical  conclusion/  l  In  a  like 
hostile  fashion  write  also  Pauly  and  France. 

How,  however,  without  a  theistical  assumption  we 
can  understand  the  origin  of  life,  the  origin  of  animals 
and  plants,  the  graduations  within  the  two  kingdoms, 
the  faculties  for  adaptation  of  the  organisms,  the 
tendency  to  people  the  air,  earth,  and  water,  etc., 
without  intervention  of  a  super-mundane  cause,  Wagner 
certainly  does  not  show  us. 

If  we  know  of  the  organisms  that  they  can  maintain 
themselves  in  construction  and  function  in  agreement 
with  altered  conditions  of  life,  that  is  nothing  more 
than  a  statement  of  the  fact  but  no  explanation  of  it. 
If  we  read  that  animals  and  plants  occupy  the  air,  the 
water,  and  the  dry  land,  and  arrange  themselves  accord- 
ingly, that  also — if  it  be  true — is  again  only  a  simple 
statement.  Or  have  air,  water,  and  land  the  tendency 
in  themselves  to  become  inhabited  ? 

Let  us,  however,  go  into  details  and  ask,  for  instance, 
how  it  comes  about  that  the  lark  rises  singing  into  the 
air,  many  flat  fish  lie  on  their  sides,  some  plants  become 
carnivorous,  why  the  plant  Duvaua  dependens  produces 
for  the  moth,  Cecidosis  eremita,  a  gall  with  a  circular 
cover  which  renews  itself  on  the  inner  side  and  is 
precisely  large  enough  to  let  the  moth  escape,  etc.  If 
it  be  assumed  that  all  this  was  not  always  so  but  has 

i  UmUldung  der  Tierwelt,  p.  79.  When  Wagner  speaks  of  scholastic 
philosophers  one  would  think  that  he  had  to  do  with  a  host  of  highly 
primitively  organized  thinkers  who  had  not  at  all  attained  to  a  proper 
'  intellectual  organ.'  Just  as  well  might  Wagner  term  '  scholastics ' 
all  who  oppose  criticism. 


CONCLUSION  233 

been  evolved,  then  does  the  question  again,  as  always, 
recur :  Why  and  wherefore  has  it  been  evolved  ? 
What  need  is  there  for  the  plant  to  keep  and  cherish 
a  moth — since  it  only  does  so  by  constant  expenditure 
of  nutrition — and  to  shape  a  cover  at  the  right  time, 
not  earlier  and  not  later,  so  that  when  the  moth  creeps 
out  of  the  gall  the  chrysalis  skin  and  that  alone  is 
torn  off  ?*  We  can  only  say  that  it  must  and  should 
happen  just  so. 

Deperet  says  appropriately  :  ~ '  In  the  time  in  which 
we  live  it  would  be  very  thoughtless  to  maintain  that  we 
satisfactorily  know  the  general  law  which  has  governed 
the  unceasing  transformations  of  organic  life  from  its 
beginning  on  the  earth  to  the  present  day.  Neither 
the  mechanical  process  of  a  physiological  adaptation, 
nor  the  immediate  influence  of  the  environment,  and 
still  less  the  struggle  for  existence,  permit  us  to  give 
a  suitable,  sagacious,  and  perfect  explanation  of  the 
magnificent  picture  presented  by  the  palaeontological 
history  of  evolution.  In  this  evolutional  history  there 
are  certainly,  without  in  itself  speaking  anywhere  of 
the  first  origin  of  life,  enigmatical  points  and  important 
facts  in  existence  whose  explanation  eludes  us/  We 
have,  it  is  true,  for  many  of  these  '  enigmatical  points/ 
catchwords  which  have  become  very  popular,  but  with 
catchwords  alone  no  problem  is  ever  solved.  In  the 

1  See  the  excellent  article,    '  Ein   Wunderwerk   der    Pflanzentechnik,' 
by  H.  Dieckmann,  S.J.,  in  Natur  und  Kultur,  1911,  p.  485. 

2  UmbiMung  der  Tierwelt,  p  114.     If  Deperet  himself  speaks  in  various 
places  of  the  '  mechanism  '  of  the  evolutionary  process,  he  always  means 
thereby  only  the  external  course  of  development. 


234  THE  THEOKY  OF  EVOLUTION 

first  decades  of  the  last  century  an  investigator  who 
desired  that  his  works  should  be  regarded  and  read  as 
scientific  had  to  write  in  the  style  of  the  Hegelian 
philosophy,  somewhat  as  Reichenbach  did.1  '  As 
the  area  of  a  circle  is  not  merely  centre-point  and  cir- 
cumference but  also  the  relations  of  both  to  each  other, 
so  in  nature  is  everything  directed,  as  in  the  thinking 
mind,  by  thesis  (precept,  centre-point,  unity),  antithesis 
(contradiction,  periphery,  multiplicity),  and  synthesis 
(equalization,  combination  of  the  contradictions,  circle 
area,  formation)/  '  The  green  plant  kingdom  arose  in 
the  Algae  from  the  water — we  saw  these  in  progressive 
formation,  always  maternally  shaped  only  into  beautiful 
types  until,  soaring  into  the  element  of  the  air,  the 
Moss  by  anthers  limited  their  forms.  The  Ferns  take 
up  into  themselves  the  budding  of  the  Algse  and  Mosses, 
and,  seeking  in  vain  to  find  a  centre  by  their  circulation, 
Cycas  and  Zamia  achieve  this  finally  by  forming  the 
acrogenetic  axis  of  growth/ 

(  Central  formation  begins  from  this  point  as  the 
type  of  the  plant  developing  itself  first  from  the  primary 
bud  of  "  Isoetes/'  But  the  node  divides  and  repeats 
itself,  and  intermediate  growths  extend  themselves  as 
stem  and  scales — as  phantom  leaves — emerge  from  the 
node,  and  the  male  is  born  and  for  him  the  primary 
female.  The  scales  require  a  stalk  and  proclaim  the 
flower  in  the  trinity  oi  the  realm  of  plants,  etc/ 

'  Empty  words  '  we  may  say,  but  the  expressions 

i  From  A.   Kerner  v.  Marilaun  :    Pflanzenleben,    II,  Leipzig-Vienna, 
1891,  p.  591. 


CONCLUSION  235 

'  spontaneous  generation/  '  natural  selection/  '  sexual 
selection/  have,  as  general  explanatory  principles  of  the 
organic  world,  just  as  little  meaning.  They  too  will 
disappear,  just  as  the  thesis,  antithesis,  and  synthesis 
have  disappeared. 

Theories  of  evolution  will  remain,  since  everything 
points  to  the  fact  that  there  was  and  is  an  evolution 
of  the  organic  world.  This  evolution,  however,  does 
not  express  itself  in  quite  impossible  spontaneous 
'  leaps '  from  the  inorganic  to  the  organic,  or  from 
plants  to  animals,  and  also  not  in  plan  and  objectless 
hither-and-thither  variation,  but  in  a  constant  main- 
tenance of  the  harmony  between  construction  and 
function  and  the  external  conditions  of  life,  and  in 
constant  development  of  the  bases,  since  '  bases  ' — and 
these,  too,  for  one  definite  end — must  exist,  as  the 
result  is  always  in  one  definite  direction — viz.  the 
purposeful,  the  vitally  capable. 

Neither  was  life  acquired  by  the  organisms  them- 
selves, nor  were  the  evolutional  tendencies  :  both  were 
received  from  another  source — from  the  Creator.1 


INDEX 


ADAPTATION  (adaptation  pheno- 
mena):  meaning  of  term,  180; 
with  particularly  peculiar  modes 
of  life — parasites  and  symbiotics 
— there  arise  peculiar  animals, 
new  systematic  species,  genera, 
and  families,  and  even  orders  and 
classes,  183  ff.,  188-202  ;  but  no 
types,  since  the  entire  change  can 
be  recognized  as  retrogression  of 
a  type,  183  ff. 

Age  of  sedimentary  deposits : 
significance  in  connection  with 
the  theory  of  evolution,  18 ; 
general  results,  21. 

Algonkium  =  pre-Cambrian. 

Angiosperms  (covered  seeds) :  first 
certain  traces  in  the  Ceenozoic 
formation,  60  ;  further  develop- 
ment, 62  f.  ;  no  connection 
with  other  groups,  64  ;  system- 
atic classification,  125. 

Animal  geography:  separation  pro- 
duces local  races  and  local 
species,  171  ;  complete  isolation 
and  in- breeding,  formation  of 
species,  genera  and  families, 
171  ff.  ;  or  '  peculiar '  fauna, 
174  ff. ;  but  no  new  types,  176. 

Animals  are  organisms  possessing 
consciousness,  108  f.,  115  ;  genetic 
connection  with  plants  (life  with- 
out consciousness)  excluded,  116 ; 
history  of  their  evolution,  23-49 ; 
systematic  classification,  117  ff. 


Ant  and  Termite  guests,  188  ff. 

BERNARD,  CL.,  91,  94. 

Biogenetic  fundamental  law,  217- 

228. 

Bumiiller,  J.,  28,  33. 
Bunge,  G.  v.,  91,  92,  101. 

CALAMARIACE^B  (Primary  Equise- 
tae) :  predecessors  in  the  Devonian 
formation  (Proto-calamariacese), 
54  ;  differentiation  of  the  groups, 
67  f . ;  retrogressive  phenomena, 
73. 

Cambrian  formation  :  animal  life, 
23  ;  plant  life,  53. 

Carboniferous  formation,  22,  28  ; 
rich  development  of  the  plant 
world,  55  ff. 

Catastrophic  ( =  creation)  theory  : 
opinions  of  Cuvier  and  his 
pupils,  9  ff.  ;  protest  against,  by 
Lyell,  Lamarck,  and  Geoffrey 
St.  Hilaire,  11  f.  ;  improbability 
of,  15  f . 

Cirripedes  as  embryological  ex- 
amples, 205  ff. 

Club-mosses,  fossil  (Lepidodendron), 
55,  56  ;  extinction  of,  60,  66. 

Convergence :  meaning  of  term, 
45 ;  convergence  phenomena  in 
animals,  45  ff.  ;  in  plants,  71. 

Copepodse  (Rudder-crabs,  Cirre- 
pods),  example  of  graduated 
retrogression,  186. 


238 


INDEX 


Cordaites  :  first  appearance  in  the 
Silurian  formation,  54 ;  further 
development,  55,  56,  60. 

Cryptogams  (non-seed  plants)  : 
history  very  imperfectly  known, 
54,  64  ;  systematic  classification, 
122  f. 

Cuvier,  G.,  9,  117. 

DARWIN,  CH.,  12,  157-163,  168. 

Darwinism :  chief  conception  of 
Darwinism  as  a  specific  hypo- 
thesis of  evolution,  157  ff.  ; 
criticism,  159  ff. 

Deperet,  Ch.,  13,  25-36,  43-48, 
162,  166,  167,  170,  226,  227, 
230  f.,  233. 

Descent,  Theory  of  :  definition  of 
the  problem,  3  ;  historical  origin, 
3-17  ;  '  Descent '  and  '  Evolu- 
tion,' 14  ;  theory  really  only  a 
postulate,  17  ;  positive  founda- 
tion of  same,  23-76,  164-228. 

De  Vries,  H.,  168. 

Differentiation  :  meaning  of  term, 
36  ;  law  of,  with  animals,  35-41  ; 
law  of,  with  plants,  67-71. 

Doflein,  F.,  182. 

Driesch,  H.,  91,  94,  159,  160,  161, 
180,  225. 

EMBRYOLOGICAL  evidence :  em- 
bryogeny  can  explain  the  former 
appearance  of  organisms,  202  ff .  ; 
examples,  205-212  ;  affords  no 
evidence  concerning  origin  of  the 
types  themselves,  216  ;  in  the 
sense  of  a  '  biogenetic  funda- 
mental law,'  must  be  discarded, 
217-228. 

Engler  and  Prantl,  Textbook  of, 
58,  63. 

Evolution  :  meaning  of  term,  13  ; 
results  of  palaeontology  regarding 


higher  formation  proper,  34, 
48  ff.  ;  results  of  palseo-botany, 
61  ff.,  75  ;  evolution  as  postulate, 
83-138. 


FERN  growth  (in  a  wider  sense). 
See  Pteridophytes. 

Ferns  (proper),  yield  the  first 
certain  plant  remains,  53,  62 ; 
differentiation  of  the  groups  in 
the  carboniferous  formation,  69  f . ; 
systematic  position,  124,  127. 

Flat  fish  (soles),  examples  of  em- 
bryological  evidence,  208  f. 

Flowering  plants.  See  Phanerogams. 

Formation,  geological,  21. 

Forms,  intermediate.  See  Transi- 
tional forms. 

Fossils,  attempts  at  explanation,  5  ; 
determination  of  age,  18  ff.  ; 
conditions  of  their  formation,  49. 

France,  R.,  150,  151,  152,  154,  155. 

Franz,  B.,  139-144. 


GENERATION,  alternation  of,  123. 

Generation,  spontaneous :  defini- 
tion, 85  ;  impossibility  of,  86-96  ; 
vain  attempts  to  render  it  com- 
prehensible, 97-108. 

Ginkgo  :  first  traces,  55  ;  true 
ginkgos,  60  ;  transformation  in 
the  Jura  formation,  71  ;  systema- 
tic position,  125,  137  ;  no  tran- 
sitional form,  132. 

Gothan,  W.,  51  f.,  61,  63,  64,  68,  71, 
74. 

Graff,  L.  v.,  178,  180,  183  ff. 

Gymnosperms  (naked-seeded) :  the 
first  representatives  (Cordaites), 
54  ff. ;  widely  distributed  in  the 
carboniferous  formation,  58  f.  ; 
greatest  development  in  the 
Mesozoic  formation,  60 ;  no 


INDEX 


239 


connection    with    other    cl 

63 ;   description  and  systematic 

position,  125  f. 


HABERLANDT,  G.,  69,  111,  113, 114, 

154. 

Hackel,  E.,  217-228,  231. 
Handlirsch,  A.,  37-41,  196,  229. 
Hartmann,  E.,  85,  92,  106,  107. 
Heffe,  R.,  165,  170,  205. 
Heidenheim,  M.,  88. 
Hertwig,  O.,  85,  87,  90  ff.,  97  f., 

104,  106,  138,  223,  224,  225. 
Hertwig,  R.,  44,  117,  118,  133,  175, 

181,  207. 
Homer,  R.,  43. 


INSECTS  :  examples  from  palaeon- 
tology to  illustrate  differentiation, 
37-41  ;  represent  the  most  sym- 
biotics,  188-202. 

Invertebrates :  in  the  Cambrian 
formation  (and  pre- Cambrian) 
already  much  divided,  23  ff.  ; 
no  connection  between  the  dif- 
ferent stocks  and  classes,  30, 
33 ;  systematic  classification, 
118. 


KAYSER,  E.,  19  ff.,  22,  27,  43,  53. 
Kerner  v.  Marilaun,  A.,  136,  138, 

234. 

Kircher,  Athanasius,  5. 
Klein,  E.,  108. 
Koken,  E.,  24,  30,  31. 


LAMARCK,  J.  B.  de,  12,  145-150. 
Lamarckism  :     basal  principles  of 

the  doctrine,  145  ff.  ;  criticism, 

148  ff. 
Lepidodendron.     See  Club-mosses. 


Life :  definition  of,  86,  88  ff.  ; 
origin  of  life  cannot  be  explained 
by  spontaneous  generation,  96- 
108 ;  omne  vivum  e  vivo,  96. 

Life,  principle  of,  foundation  of 
same,  93  ff. ;  various  appellations, 
93  ff.  ;  it  stands  above  material 
energies,  94  ff. ;  life  of  animals, 
115  f. 

Lizards  :  example  as  embryological 
evidence,  211  ff. 

Lotsy,  J.  P.,  55,  58,  59,  131,  168, 
170. 

Lucas,  F.,  110,116. 

Lusus  Naturae,  5  ff. 


MERESCHKOWSKY,  C.,  103  f. 

Mountains,  Primary,  or  archaic 
formation  groups,  22,  52. 

Muckermann,  H.,  85,  199. 

Mutations,  168  f. 

Myrmecophils  and  Termitophils : 
meaning  of  terms,  188  ;  examples 
for  formation  of  new  systematic 
species,  genera,  and  families  by 
symbiosis,  188-202. 


NAEGELI,  K.  W.,  80,  85,  102,  103, 
104. 

Nauplius  larva,  205. 

Nee-Darwinism,  163. 

Neo-Lamarckians  :  chief  public  re- 
presentatives, 150 ;  their  doc- 
trine, 150-156,  231  f. 

Neo-Lamarckism  :  basal  principles 
of  the  doctrine,  150  ff. ;  criticism, 
152-156. 


OLIVER,  F.  W.,  58,  73. 

Organism :  preliminary  explana- 
tions, 86  ;  more  exact  definition, 
95. 


240 


INDEX 


PALAEONTOLOGY,  results  of :  con- 
cerning animal  development, 
23-49  ;  concerning  plant  develop- 
ment, 49-76  ;  comparison  with 
the  results  of  systematic  classi- 
fication of  the  present  animals 
and  plants,  129-138 ;  palaeon- 
tology and  the  '  basal,  bio- 
genetic  law,'  225  ff.,  231. 

Palseontological  law  of  evolution  : 
for  animals,  34-49  ;  for  plants, 
65-75. 

Parasites  (parasitism) :  meaning  of 
term,  178  ;  parasites  may  be 
recognized  as  retrograded  forms 
of  a  definite  type  (by  adaptation), 
179,  183  ff.  ;  probable  origin  of 
parasitism,  183,  187  ;  parasitism 
gives  rise  to  peculiar  forms, 
impure  '  orders  '  and  '  classes,' 
183  ff. 

Parasitica :  example  for  embryo- 
logical  evidence,  206  f. 

Pauly,  A.,  147,  150,  152,  154,  155, 
156. 

Perfection,  grades  of  (heights  of 
organization) :  criteria  (higher 
differentiation),  118  ;  extent  of 
the  purposeful  relations  with  the 
outer  world,  139  ff.  ;  equivalent 
to  '  types,'  229. 

Pfeffer,  W.,  91,  113. 

Phanerogams  (seed  or  flowering 
plants) :  first  occurrence  in  the 
Silurian  formation  (Cordaites), 
54  ;  further  development,  55  ff.  ; 
no  genetic  connection  between 
the  various  classes,  64 ;  sys- 
tematic classification,  125  f. 

Plant  geography.  See  Animal  geo- 
graphy. 

Plants :  are  those  living  beings 
which  display  no  consciousness 
and  therefore  have  none,  110  f.  ; 
assumed  sense  organs  in  such 


organisms,  115  f.  ;  spontaneous 
transformation  to  animals,  i.e. 
to  beings  with  consciousness, 
excluded,  116  f . ;  systematic 
classification,  122-129. 

Plants,  fossil :  first  certain  traces 
in  the  Silurian  formation,  53  ; 
process  of  evolution,  54-62. 

Postulates  of  the  theory  of  evolu- 
tion, 80  ff.  ;  examination  of  the 
chief  postulates,  83-138. 

Potonie,  H.,  50,  55,  68,  72,  73. 

Pre-Cambrian  formation  (Algon- 
kian)  :  discoveries  of  fossils,  23. 

Proto  -  calamariaceae.  See  Cala- 
mariacese. 

Pteridophytes :  form  the  greater 
part  of  the  carbonaceous  flora, 
55,  60  ;  systematic  position,  124  ; 
classes,  127. 

Pteridosperms,  58  ff.,  63,  132. 


REGRESSION,  law  of,  with  animals, 
44  f.,  181  ;  with  plants,  73  ff., 
186  ;  regression  and  rudiment, 
213  ff. 

Reinke,  L,  64,  71,  85,  91,  94,  95, 
101,  104,  106,  107,  136,  138. 

Rudiments,  definition  of,  213  ;  cri- 
teria of  existence,  214  ;  examples, 
215  f .  ;  unreliable  acceptance 
of  so-called  '  rudiments,'  217- 
228. 


SALAMANDER,  example  of  embryo- 
logical  evidence,  209  ff. 

Scheuchzer,  J.  J.,  6. 

Seed  plants.     See  Phanerogams. 

Selenka,  E.,  118ff. 

Sigillaria,  56,  60,  66  ;  predecessors, 
54  ;  differentiation  of  the  groups, 
27. 

Sinety,  R.,  157. 


INDEX 


241 


Specialization :  meaning  of  term, 
36  ;  law  of,  with  animals,  35-41  ; 
law  of,  with  plants,  67-71. 

Species,  systematic,  definition  of,  1. 

Specific  constancy,  theory  of : 
supporting  points,  4  ;  not  estab- 
lished in  its  original  sense,  164- 
228. 

Spontaneous  Generation.  See  Gen- 
eration. 

Steinmann,  G.,  29,  31  ff.,  47,  66, 
138,  230  f. 

Strasburger,  Noll,  Schenk,  and 
Schimper,  textbook  of,  91,  112. 

Symbiotics  (symbiosis) :  definition, 
177  f. ;  recognizable  as  '  adapted ' 
forms,  188-202  ;  symbiosis  leads 
up  to  the  formation  of  new 
families,  189, 193,  202. 

Systematic  classification :  system- 
atic categories,  1  f .  ;  the  higher 
categories  (stocks,  classes,  orders) 
show  no  genetic  connection 
according  to  palseontological 
research,  33,  48  f.,  62  ff.,  75; 
principles  of,  117-129 ;  the 
higher  categories  at  least  are 
primary  grades  of  perfection, 
131,  136  f.,  229. 


TAPEWORMS,  examples  of  graduated 

retrogression,  183  ff. 
Termitophils.     See  Myrmecophils. 
Transitional    forms,     phylogenetic 
—  intermediate)  forms  :   Stego- 

cephali,  31 ;  of  the  insects,  37  f. ; 

in  plants  (Pteridosperms),  58,  63  ; 

general   principles   for   deciding 


apparent     intermediate     forms, 
130  ff. 

Types :  meaning  in  systematic 
classification,  117 ;  description 
of  the  generally  accepted  types 
of  the  animal  and  plant  kingdoms, 
118-129  ;  actual  number  of,  137  ; 
a  type  is  always  a  constantly 
maintained  grade  of  perfection, 
137  f.,  229. 

VARIABILITY  of  organisms  through 
the  direct  influence  of  the  life 
conditions,  164-168;  kind  of 
variation,  168  ff. ;  by  isolation 
and  in-breeding,  170—177 ;  by 
the  influence  of  changed  modes 
of  life,  178-228. 

Vertebrates  :  lacking  in  the  Cam- 
brian formation,  23  ;  first  ap- 
pearance in  the  Silurian,  27 ; 
succession  of  the  classes,  28  ;  no 
connection  between  the  different 
classes,  31  ff.  ;  systematic  classi- 
fication, 119. 

Verworn,  M.,  92. 


WAGNER,  A.,  147,  148,  150,  151, 

152, 154,  155,  156,  231  f. 
Walther,  J.,  43. 

Warnung,  E.,  73, 122-128, 135, 136. 
Wasmann,  E.,  4,  41,  87,  115,  116, 

188,  189,  202,  214. 
Weismann,  A.,  163,  170. 
Wilson,  E.  B.,  98, 100. 


ZITTEL,  K.,  7,  53,  54,  68,  225. 


Spottiswoode  &  Co.  Ltd.,  Printers,  Colchester,  London  and  Eton. 


IMPORTANT    WORKS    ON    EVOLUTION 
By  FATHER  ERICH  WASMANN,  S.J. 


Medium  8vo.  57O  pages.  Price  16s. 

Modern    Biology 

AND 

The  Theory  of  Evolution 

Translated  from  the  Third  German  Edition  by 
A.    M.    BUCHANAN,    M.A. 

With  8  Plates  and  54  Textual  Illustrations. 

Extract  from  Preface  : — '  I  have  spoken  as  a  Christian  engaged  in  scientific 
research,  and  I  am  firmly  convinced  that  natural  truth  can  never  really 
contradict  supernatural  revelation,  because  both  proceed  from  one  and  the 
same  source,  viz.  the  everlasting  wisdom  of  God.  Therefore  the  study  of 
modern  biology  and  of  the  theory  of  descent,  if  carried  011  without  prejudice, 
can  tend  only  to  the  glory  of  God.' 

'  An  interesting  and  valuable  work,  by  a  Jesuit  Father,  whose  original  work  upon  ants 
in  especial  has  made  his  name  honoured  wherever  biologists  are  to  be  found.  .  .  .  The 
book  is  one  to  read  and  possess,  taking  its  own  place,  undoubtedly,  in  the  biological 
literature  of  our  epoch.' — Pall  Mall  Gazette. 

'  Will  be  welcomed  by  Catholic  students  in  the  realm  of  biology.  Father  Wasmann  has 
made  all  knowledge  in  that  sphere  his  own.' — Catholic  Times. 

'  Father  Wasmann's  book  has  attracted  great  attention  both  among  scientists  and  the 
public,  Catholic  and  anti-Catholic,  in  Germany  .  .  .  his  exposition  of  modern  biology  is 
confessed  by  his  critics  to  be  admirable.  As  a  proof  that  the  Jesuit  controversialist  has 
not  lost  his  ancient  skill  in  dialectics  the  book  is  indiibitable." — Saturday  Review. 

'  The  book  is  exceedingly  interesting  and  has  considerable  scientific  value,  for  Father 
Wasmann  is  not  only  an  able  and  courteous  controversialist,  but  is  also  a  zoologist  of  no 
mean  ability.'— Oittloofc. 


Demy  8vo.       28O  pages.       Price  6s.  net. 

The  Problem  of  Evolution 

Being  a    full   Report  of  the   Lectures   given   in    Berlin   in   February, 
1907,  and  of  the  Discussion  thereon. 

Authorised  Translation. 

'From  cover  to  cover  the  book  is  an  intellectual  treat.' — Catholic  Times. 

'  The  lectures  are  interesting  as  a  lucid  statement  of  the  position  taken  by  the  Roman 
Catholics  as  to  the  bearing  of  evolution  on  Theism  and  Atheism.' — Scotsman. 

'  The  learned  Jesuit  is  both  a  philosopher  and  a  zoologist  .  .  .  We  recommend  all  who 
are  interested  in  the  philosophic  aspects  of  scientific  research  to  read  Father  Wasmann's 
able  defence  of  the  Theistic  evolution.'—  Downside  Review. 

KEGAN  PAUL,  TRENCH,  TRUBNER  &  CO.,  LTD., 

BROADWAY  HOUSE,  68-74  CARTER  LANE,  LONDON,  E.G. 


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Frank,  K. 

theory  of  evolution. 


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