368 The Study of Animal Life app. 



student will naturally pass to the works of Darwin himself — Th& 

 Origin of Species by means of Natural Selection; or, the Pre- 

 servation of Favoured Rcues in the Stfuggle for Life (Lend., 

 1859) ; The Variation of Animals and Platits under Domestication 

 (2 vols., Lond., 1868); The Descent of Man, and Selection in 

 Relation to Sex (Lond., 1871), etc. ; the earlier works of Wallace, 

 especially his Contributions to the Theory of Natural Selection 

 (Lond., 1 871); Spencer's Principles of Biology — cf his articles 

 on " The Factors of Organic Evolution " {Ninetee?ith Cetitttry, 

 1 886) ; Haeckel's Generelle Morphologie, and Natural History of 

 Creation. As a popular account of Darwin's life and work. Grant 

 Allen's Charles Darwin (English Worthies Series, 3rd ed., Lond., 

 1886) has a deserved popularity; G. T. Bettany's similar work 

 (Great Writers Series, Lond., 1886) has a very valuable biblio- 

 graphy ; but for full personal and historical details reference must 

 be made to the Life and Letters of Charles Darwin, by his son 

 Francis Darwin (3 vols., Lond., 1887). 



Recent Contributions to the Theory of Evolution. — 



At the present time there is much discussion in regard to the 

 factors of organic Evolution. The theory of Evolution is still 

 being evolved ; there is a struggle between opinions. On the 

 one hand, many naturalists are more Darwinian than Darwin was, 

 — that is to say, they lay more exclusive emphasis upon the theory 

 of natural selection ; on the other hand, not a few are less Darwinian 

 than Darwin was, and emphasise factors of Evolution and aspects 

 of Evolution which Darwin regarded as of minor importance. 



Of those who are more Darwinian than Darwin, I may cite as 

 representative : Alfred Russel Wallace who, in his Darwinism, 

 subjects Darwin's subsidiary theory of sexual selection to destructive 

 criticism ; August Weismann who, in his Essays on Heredity, 

 denies the transmissibility of characters acquired by the individual 

 organism, as the results of use or disuse or of external influence ; 

 and E. Ray Lankester. see his article "Zoology" in the Encyclo- 

 pcedia Britannica, and his work on the Advaiuement of Science 

 (Lond., 1890). The student should also read an article by Prof. 

 Huxley, "The Struggle for Existence, and its Bearing upon ^lan" 

 in the Nineteenth Century, Feb. 1888. 



See also : — 

 Samuel Butler, Evolution Old and New (Lond., 1879), Luck or 



Cunning {hond. , 1887), and other works. 

 Prof. E. D. Cope, Origin of the Fittest {New York, 1887). 

 Prof. G. H. T. Eimer, Organic Evolution, as the Result of the 



Inheritance of Acquired Characters, according to the Laws of 



Organic Growth (Jena, 1888). Trans, by J. T. Cunningham 



(Lond., 1890). 



