8 The Mechanism of Evolution in Leptinotaesa 



conditions. 



Characters that may be described as conditions in the mass are present as 

 completely in organisms as they are in non-living substance, and in organisms 

 these characters concern many of the reactions and behaviors that are present 

 and that are so easily modifiable. These in the non-living are the product of 

 the nature of the substance as constituted by its factors productive of the specific 

 properties and the conditions of the medium, of which many common examples 

 will at once occur to the reader. In organisms many of the tropic activities and 

 " animal-behavior " characters are of this kind. They may be held in one con- 

 dition by retention of the same condition in the mass and one set of conditions 

 in the medium, or at any time altered, without in any manner changing the 

 nature of the substance itself, and of these changes I have presented several 

 examples in later portions of these reports. The characters in organisms that 

 are of the nature of conditions are in many instances of great importance in the 

 economy of the organism, and serve immensely vital roles in the processes of 

 conservation and equilibration as well as in the phenomena of migration, distri- 

 bution, and apparent composition. 



It will, I believe, be at once perceived that the three categories of characters 

 recognized are not only present in organisms as they are also present in the 

 non-living, but that this recognition of the nature of the different categories 

 present in organisms will aid in the further investigation of many problems. It 

 will be possible from this basis to clearly differentiate and formulate the prob- 

 lems of experimental investigation, and in some directions there appears at once 

 a clearer understanding of many problems and results. 



The chief advantage gained is the conception of the categories of the char- 

 acteristics of natural things, living and non-living, from one point of view, and 

 in this there must be at the least an element of permanent truth, since both are 

 the products of the same elements and of the same general types of physical and 

 chemical action. 



The literature upon the evolution problems has dealt and must properly deal 

 with the characteristics of organisms, but unfortunately there is an ever- 

 present " biological aspect " to these writings and failure to look at the prob- 

 lems of evolution from purely physical aspects in the majority of instances. 

 Many harmful metaphysical concepts and methods of expression have gained 

 entrance to the evolution literature; nevertheless I believe evolution problems 

 should be conceived of in a purely mechanistic physical sense, devoid of utilities, 

 purpose, motive, or " forces of evolution." 



EVOLUTION AND TRANSMUTATION. 



That there are in nature different kinds of living substance, each constant 

 in form and continued in endless series of generations as far as our observations 

 go; that there has existed in the past an innumerable array of these specific 

 kinds of substance and that the history of living nature on this planet, as dis- 

 covered, shows changes of the characters and in the historical sequence of these 

 forms, are undeniable facts. For the most part the facts of the history of life 

 upon this planet are isolated, but suggest to us nevertheless continuity of change 

 in the past, in conformity with some natural principle of causation, and hence 

 there have arisen diverse hypotheses of the causation of this diversity and the 

 sequence of events in the different phyla of the living world. 



