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are published in Chicago. They include the following: "The 

 Marriage Problem" (1888), "Ethical Evolution" (1889), "On 

 the Material Relation of Sex" (1890), "Foundations of Theism" 

 (1893), "The Effeminization of Man" (1893), "The Present 

 Problems of Organic Evolution" (1895), and "Primary Factors 

 of Organic Evolution" (1896). These essays in time formed the 

 basis of chapters or even constituted chapters themselves in the 

 works that he subsequently published. Many of those that ap- 

 peared in Chicago were collected and woven into the volume enti- 

 tled The Primary Factors of Organic Evolution, which was pub- 

 lished in 1896. This work he describes as "an attempt to select 

 from the mass of facts accumulated by biologists, those which, in 

 the author's opinion, throw a clear light on the problem of organic 

 evolution, and especially that of the animal kingdom." 

 The evidence presented is chiefly paleontological. He says: 



"In the search for the factors of evolution, we must have first 

 a knowledge of the course of evolution. This can only be obtained 

 in a final and positive form by investigation of the succession of 

 life. The record of this succession is contained in the sedimentary 

 deposits of the earth's crust, and is necessarily imperfect. Advance 

 in knowledge in this direction has, however, been very great of 

 recent years, so that some parts of the genealogical tree are toler- 

 ably or quite complete. We hope reasonably for continued prog- 

 ress in this direction, and if the future is to be judged of by the 

 past, the number of gaps in our knowledge will be greatly lessened. 

 In the absence of the paleontological record, we necessarily rely 

 on the embryologic, which contains a recapitulation of it. The 

 imperfections of the embryonic records are, however, great, and 

 this record differs from the paleontologic in that no future dis- 

 covery in embryology can correct its irregularities. On the con- 

 trary every paleontologic discovery is an addition to positive 

 genealogy." 



Mention is appropriate at this place of his contribution of a 

 paper on "Evolution in Science and Art" to the Evolution Series 

 of the Brooklyn Ethical Association in 1891. He also prepared 

 one of the lectures in the series published over the title of Half 

 Hours with Modern Scientists, and he was the author of the article 

 on "Comparative Anatomy" contained in the Universal Cyclopedia, 



