CONTENTS. vu 



PAGE. 



selection, a discredited theory, for the support of the 

 natural selection theory, 85. Natural selection rests on an 

 unwarranted assumption of its homology with artificial 

 selection, 86. Many biologists find natural selection 

 unable to account for known biologic conditions, 89. Sig- 

 nificance of the concessions of Darwinians, 90. Kor- 

 schinsky's extreme anti-Darwinian doctrine, 91. Delage's 

 "true role of selection, "93. Morgan's rejection of natural 

 selection as a species-forming factor, 93. 



APPENDIX: Gal ton's statement of the law of regression, 

 97. Wolff's criticism of panmixia, 98. Example of inef- 

 fective panmixia, 100. Example of progressive degenera- 

 tion inexplicable by natural selection, 100. Wolff's 

 discussion of the selection coefficient, 101. Example of 

 non-selection of trivial differences, 103. References to 

 books and papers on plant breeding, 105. 



CHAPTER V. 



DARWINISM ATTACKED (Continued)-. THE THEORY 



OF SEXUAL SELECTION . . .... .106 



Secondary sexual differences or characters, 107. Classi- 

 fication of secondary sexual characters, 107. Useless and 

 harmful characters not explicable by natural selection, 

 no. Theory of sexual selection to account for them: the 

 theory defined, in. Darwin's assumptions as basis of the 

 theory of sexual selection, 112. Difficulties in the way of a 

 general application of the theory, 113. The theory appli- 

 cable only to species in which males are more numerous 

 than females, 113. The passivity of females, 114. Males 

 of species in which no real pairing occurs also show strik- 

 ing secondary sexual characters, 114. Necessity of 

 assuming unproved aesthetic development among lower 

 animals, 114. Few recorded cases of observed choosing 

 by female, 115. Difficult to assume utility for many 

 secondary sexual characters, 115. Stolzmann's case of the 

 Andean humming-birds, 116. How explain the beginnings 

 of secondary sexual characters, 117. How explain orna- 

 mental characters appearing in both males and females, 

 118. Morgan's objections to sexual selection theory, 118. 

 Experimental evidence touching the theory is against it, 

 1 20. Mayer's experiments with Promethea and Porthetria 

 moths, 121. Douglass's and Diirigen's observations on 



