PREFACE. 



The data and conclusions presented in part in this volume are the product 

 of a project in which it was attempted to attack the " evolution problem " in 

 one set of organisms from a number of different aspects. Evolution in organ- 

 isms must be conceived of as the product of the interaction of internal and 

 external factors, operating in strict mechanistic manner, as in non-vital phe- 

 nomena, so that the central problem was the determination and proof of the 

 mechanism of action of these two groups of factors whose operations are pro- 

 ductive of evolutionary changes. Experimental analysis of the problems, prose- 

 cuted with rigor and thoroughness, has been held to be the only means of 

 progress. Before this ideal could be applied much preliminary clearing of the 

 ground had to be done, and to this I gave the necessary attention in a report 

 published under the title "An Investigation of Evolution in Chrysomelid 

 Beetles of the Genus Leptinotarsa." * 



The results of the project have been the development of a mechanistic concep- 

 tion of evolution based upon the interplay of genetic and environic factors and 

 the demonstration that the methods of evolution are heterogeneous, even in 

 one group of organisms. The basis of all methods of change is found to be 

 directly the product of the nature of the genetic factors of composition and 

 their capacity for diverse modes of reaction, especially with factors of the 

 environic complex. Purpose, utility, and kindred concepts have found no sup- 

 port, every change appearing as the chance mechanistic product of the reacting 

 agents ; while the product of the reaction either was able or not able to operate 

 under the conditions of origination, so that survival is decided at once and not 

 after long and faltering trials. 



The project as organized consists of three parts, each necessary to the success 

 of the others and to the hope of arriving at a knowledge of the mechanism of 

 evolution that is not based upon plausibility and the arrangement of isolated 

 facts upon the fabric of preconceived theory. 



The first stage (reported upon in the publication referred to) must deal with 

 the discovery and testing of some limited set of organisms in nature that are 

 possible subjects for study and especially for the experimental portions of the 

 investigation. Further, it is necessary to become fully acquainted with the 

 organisms in nature and to make preliminary tests to discover whether it is 

 possible to produce permanent changes in the material and the probable success, 

 if any, that might be expected from an experimental attack upon this portion 

 of the problem. 



The second portion, given a successful outcome of the first, must comprise a 

 rigorous experimental investigation of the factors of evolution and an attempt 

 to create new attributes and qualities not existing in nature in the materials, 

 and to discover the relation of these to old characters and their interaction when 

 brought into combination or into competition with existing characters. With 

 this vantage gained, it will then be possible to create in the laboratory new 



* Carnegie Inst. Wash., Pub. 48, 330 pp., 30 pi., 31 text figs., 1906. 



Ill 



