CHAP. xxi. ORIGIN OF SPECIES, 407 





CHAPTER XXL 



ON THE ORIGIN OF SPECIES BY VARIATION AND NATURAL 



SELECTION. 



MR. DARWIN'S THEORY OF THE ORIGIN OF SPECIES BY NATURAL 



SELECTION MEMOIR BY MR. WALLACE MANNER IN WHICH FAVOURED 



RACES PREVAIL IN THE STRUGGLE FOR EXISTENCE FORMATION OF 

 NEW RACES BY BREEDING HYPOTHESES OF DEFINITE AND INDEFINITE 

 MODIFIABILITY EQUALLY ARBITRARY COMPETITION AND EXTINCTION 



OF RACES PROGRESSION NOT A NECESSARY ACCOMPANIMENT OF 



VARIATION DISTINCT CLASSES OF PHENOMENA WHICH NATURAL 



SELECTION EXPLAINS UNITY OF TYPE, RUDIMENTARY ORGANS, GEO 

 GRAPHICAL DISTRIBUTION, RELATION OF THE EXTINCT TO THE LIVING 

 FAUNA AND FLORA, AND MUTUAL RELATIONS OF SUCCESSIVE GROUPS 

 OF FOSSIL FORMS LIGHT THROWN ON EMBRYOLOGICAL DEVELOPMENT 



BY NATURAL SELECTION WHY LARGE GENERA HAVE MORE VARIABLE 



SPECIES THAN SMALL ONES DR. HOOKER ON THE EVIDENCE AFFORDED 

 BY THE VEGETABLE KINGDOM IN FAVOUR OF CREATION BY VARIATION 

 SEFSTROM ON ALTERNATE GENERATION HOW FAR THE DOCTRINE 



OF INDEPENDENT CREATION IS OPPOSED TO THE LAWS NOW GOVERNING 

 THE MIGRATION OF SPECIES. 



FOR many years after the promulgation of Lamarck's doc 

 trine of progressive development, geologists were much 

 occupied with the question whether the past changes in the 

 animate and inanimate world were brought about by sudden 

 and paroxysmal action, or gradually and continuously, by 

 causes differing neither in kind nor degree from those now in 

 operation. 



The anonymous author of ( The Vestiges of Creation ' pub 

 lished in 1844 a treatise, written in a clear and attractive 

 style, which made the English public familiar with the lead 

 ing views of Lamarck on transmutation and progression, but 

 brought no new facts or original line of argument to sup- 



