Chapter IX

PROOFS FROM VARIATION OF ORGANIC FORMS, ARTIFICIAL AND NATURAL.

_Limitation of the use of experiment in morphology_--Unconscious
experiments in breeding, and their results--Principles
involved--Inheritance, immediate and ancestral--Effect of
true breeding long continued--Method of selection illustrated
by diagram--Formation of a race--Process the same in nature
--Show selective effect of physical environment--Of organic
environment--Of migrations--Of unlimited time--Other
factors of change, and their effects shown in nature and in
domestication--Differences between artificial and natural
species 222

_First difference, reversion_--The tendency to reversion
described--The reason explained--Illustrated by the case of
the pointer 229

_Second difference, intermediate forms_--Reason is, these are
eliminated in nature 232

_Third difference, cross-fertility_--Natural species are usually
cross-sterile--Degrees of cross-sterility--Two bases of
species, morphological and physiological--Two kinds of
isolation, sexual repugnance and cross-sterility--Latter most
essential--Illustrated by plants and hermaphrodite animals--
Former only higher animals--Natural laws interfered with by
domestication--Illustrated by plants and animals 232

_Law of cross-breeding_--Effect of close breeding--Of crossing
varieties to a limit--The law investigated--Reproduction in
lowest organisms--Fission--Gemmation--Internal gemmation
--Sex introduced--Effect of, is funding of differences in
offspring and tendency to variation--Sexual and non-sexual
reproduction compared--Separation of sex elements--
Of sex-individuals--Introduction of sex-attraction--
Funding of greater differences in offspring--Crossing of
varieties--Diagram illustrating effect in vigor--Effect
also in plasticity--Application of these principles--
Necessity of sexual isolation to produce species--Origin of
cross-sterility and thus of species by Dr. Romanes’s idea--
Why artificial varieties are cross-fertile--Geographical
species sometimes cross-fertile--Application of principles--
Absence of intermediate links in natural species explained--
Under what conditions such are found--Further explanation of
this point--Illustrated by a growing tree 236

_Objection answered_--Intermediate links ought to be found fossil
--Answer (1) Imperfection of record. (2) The term species
indefinite. (3) Transitions between all other taxonomic groups
abundant. (4) Between species, also, both living and fossil
--Of fossil, Planorbis of Steinheim--Other examples--(5)
Why transition-forms are rare--Answer--Changes in every
department of nature are paroxysmal--Illustrated--So the
steps of evolution paroxysmal--Critical periods in evolution
--Causes of rapid advance--Apparent discontinuity between
species--(1) changes paroxysmal--(2) Brooks’s idea--Male
sex is the progressive element--Illustrated by society--
Effect of prosperous times--Mrs. Treat’s experiments--Hard
times produce excess of males, and therefore tend to diversity
--Summary 248

_Objection_--Egyptian drawings and mummy plants, show no change
--Answer (1) Time too short. (2) We are now in time of slow
change. (3) All species don’t change, most become extinct. (4)
Evolution is probably slower now than formerly--Reasons for
so thinking--Organic evolution approaching completion--
Other supposed objections 265

_Origin of beauty_--Explanation of, in higher animals--In
flowering plants--But in many cases we can’t explain 269

_Incipient organs_--Difficulty of explaining--But these are
not objections to the _fact_ of evolution, but only to the
sufficiency of the present _theories_ of evolution. Therefore,
all discussion concerns special theories. The fact of evolution
is certain 270

PART III.

_THE RELATION OF EVOLUTION TO RELIGIOUS THOUGHT._

CHAPTER I.

INTRODUCTORY.

_Evolution if true affects every department of thought_--What
will be its effect on religious beliefs?--Objection that
truth-seeker has nothing to do with effects--Answered 275

_Relation of the true and the good_ 277

_Relation of philosophy to life_--The three necessary elements
of a rational philosophy--Application to the case in hand--
And the subject of Part III justified--Exaggerated fears--
Different forms of the conflict of science and religion--(1)
Heliocentric theory--First effect and final result--(2) Law
of gravitation--Effect and result--(3) Antiquity of the
earth and cosmos--Effect and result--(4) Antiquity of man
--(5) Evolution 277