536 THE POPULAR SCIENCE MONTHLY 



We follow the cycle of his reflection beginning with "adaptation" 

 as the great mystery to be solved ; in the middle and sanguine period of 

 life, "adaptation" is regarded as fully explained by natural selection; 

 in the closing and conservative period of life " adaptation " is again 

 regarded in some of its phases as entirely beyond human powers of inter- 

 pretation, not only in the evolution of the mental and spiritual nature of 

 man, but in such marvelous manifestations as the scales of butterflies 

 or the wings of birds. 



From our own intellectual experience we may sympathize with the 

 rebound of maturity from the buoyant confidence of the young man of 

 thirty-five who finds in natural selection the entire solution of the problem 

 of fitness which has vexed the mind and aroused the scientific curiosity 

 of man since the time of Empedocles. We have ourselves experienced a 

 loss of confidence with advancing years, an increasing humility in the 

 face of transformations which become more and more mysterious the 

 more we study them, although we may not join with this master in his 

 appeal to an organizing and directing supernatural principle. Younger 

 men than Wallace, both among the zoologists and philosophers of our 

 own time are giving a somewhat similar metaphysical solution of the 

 eternal problem of adaptation, which still baffles and transcends our 

 powers of experiment and of reasoning. 



List of Books of Alfred Eussel Wallace, O.M., F.R.S., etc. 



Sent to the author of the present article in a letter of May 3, 1912. 



"In accordance with your request I herewith send you a list of my published 

 books. The delay has been caused by the only complete copy I had having been 

 sent away for publication. 



"I have always intended to make out a complete list of my various com- 

 munications to periodical literature, but have hitherto been unable to find time 

 to do so. All my scientific communications, however, will be found in the Eoyal 

 Society's Catalogue of Scientific Papers which no doubt you have access to." 



1. "Palm Trees of the Amazon and their Uses." Pub. 1853. 



2. "A Narrative of Travels on the Amazon and Rio Negro, with an Account of 

 the Native Tribes and Observations on the Climate, Geology and Natural 

 History of the Amazon Valley." Pub. 1853, new edition 18S9. 



3. ' ' The Malay Archipelago, the Land of the Orang-utan and the Bird of Para- 



dise. A Narrative of Travel with Studies of Man and Nature." First edi- 

 tion LS69 (2 vols.). Tenth edition 1898 (1 vol.). 



4. "Contributions to the Theory of Natural Selection." Pub. as single vol. 



1870. Pub. with "Tropical Nature" in 1 vol. 1891. 



5. "Miracles and Modern Spiritualism." Pub. 1S74. Revised edition 1896. 



6. "The Geographical Distribution of Animals, with a Study of the Relation of 



Living and Extinct Faunas as Elucidating the Past Changes of the Earth's 

 Surface." Pub. 1876 (2 vols.). 



7. "Tropical Nature and Other Essays." Pub. 1 vol. 1878. Pub. with "Nat- 



ural Selection" in 1 vol. 1891. 



8. "Australasia." Stanford's Compendium of Goojxrapliy and Travel. Pub. 



1879, 3d edition 1883. New edition 1893, 1st vol., ".\ustralia and New 

 Zealand. ' ' 



