Primary (Originative) Factors. 
SUMMARY OF EVOLUTION THEORIES. 
SUMMARY OF EVOLUTION THEORIES 
(Axiom or Truism.) 
Changes are all ultimately due to the External Influences 
and the Nature of the Organism, z.e. of Protoplasm. 
813 
( Environment.) 
Changes in the 
environment are 
followed by changes 
in the organism, 
either — | or (4) in 
(2) in its | its germ 
body, cells, 
or (c) in (4) through 
(2) (?). 
(Result of (a) * En- 
- wtronmental Modi- 
Jications.”*) 
Degree of trans- 
missibility unknown. 
Such environ- 
mental modifications, 
IF transmissible, and 
if the originating con- 
ditions persist for 
some time, might 
perhaps give rise to 
new species, especi- 
ally if favoured by 
natural selection and 
isolation, In the 
individual lifetime 
Secondary (Directive) Factors. 
they may serve to 
shield the incipient 
stages of vardations 
in a similar direction.) 
(Organism.) 
Germinal varia- 
tions arising from 
the nature of pro- 
toplasm, or from 
changes in the 
nutritive environ- 
ment of the germ 
cells, or from the 
changes necessarily 
associated with fer- 
tilisation, may. be 
continuous or dis- 
continuous, quanti- 
tative or qualitat- 
ive, etc. 
( Variations.) 
Such variations 
probably supply the 
usual material for 
the origin of new 
species, for the 
establishment of 
which, more or less 
natural selection 
(elimination) and 
isolation must be 
necessary, according 
to the nature of the 
variation. 
(Function. ) 
Use and disuse of 
parts, or change of 
‘function (due to 
change of environ- 
ment or to ger- 
minal change), are 
followed by changes 
in—(q@) the body of 
the organism, or (4) 
in the gerin cells, 
either directly or (?) 
through (a). 
(Result of (a) ‘“Func- 
tional Modifica- 
tions.’’) 
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Degree Of transmis- 
sibility unknown. 
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Such functional 
modifications, IF 
transmissible, and 
if the originating 
conditions persist 
for some time, might 
perhaps give rise to 
new species, espe- 
cially if favoured 
by natural selection 
and isolation. In 
the individual life- 
time they may serve 
to shield the in- 
cipient stages of 
variations in a 
similar direction. 
‘saBueyD Jo USC 
“sotoads jo UISIIQ 
