20 The Mechanism of Evolution in Leptinotaksa 



organisms is the product of operations within this domain. They supply to the 

 race the qualities, attributes, and conditions, the modified old, the new char- 

 acteristics, either in combinations or separate, arranged to produce the specific 

 living kinds or species which must after their formation by the operations 

 mentioned be subjected to the tests of the factors of conservation, and lastly to 

 the processes of equilibration. 



CONSERVATION. 



The factors of conservation are those natural relations of the internal and 

 external factors of every organic kind whose relations determine at once and for 

 all whether or not the organism can persist. This is perhaps a synonym 

 of natural selection, but natural selection is employed in so many ways to 

 mean an agency productive of diversity, or as an agent which is productive only 

 of elimination, that I prefer the term " conservation " as indicating those 

 operations in which the newly arisen mechanism is tested out and it is proven 

 by test whether it is able or not to survive under the conditions into which it is 

 thrust by the process of origination. This is a complex test and it can only be 

 investigated by exact experimental analysis. No information can come from 

 the routine collecting of statistics and their treatment in biometric fashion, 

 and thus far the only information that I have been able to obtain concerning the 

 operation of the processes comes from experimental test in which it must be 

 proven what the specific eliminating factors are and how they work in the 

 system. I have experimentally tested a number of examples in this investiga- 

 tion, and in every instance it has been found that elimination or failure to pass 

 the test of conservation is entirely due to the factorial composition of the 

 organism, and that a factor of one kind or another by its very presence forces 

 upon the organism either in mode of action, or in some quality, attribute, or 

 condition, relations or methods of reaction such that in some portion of its life 

 the relations between external and internal can no longer be maintained, and 

 the organism is either eliminated by its own death or the race is eliminated by 

 the inability of the organism to reproduce itself under the conditions. 



I have thus far failed to find any influence of those selection effects, and in 

 every instance elimination, as far as I have observed it and tested it in these 

 and other organisms, involves little of the " biological content," and is largely, if 

 not entirely, a matter of physical relationship between the factors of composition 

 within the organism and the physical factors of existence without, in the- 

 medium. This aspect of the problems of evolution at the present moment needs 

 extensive experimental testing, and must be carried out, in order to obtain the 

 best results, in combination investigations in the laboratory and in nature, and 

 in this investigation I have been fortunate in the nature of my material and 

 with the facilities which the American continents have afforded for various 

 types of experimentation in nature. 



EQUILIBRATION. 



When an organism has passed, if by its original constitution it succeeds in 

 passing, through the test of conservation, it must then meet an added series of 

 problems in the activities which are characterized equilibration, which are those- 

 activities whereby the organism, without changing its qualities, so adjusts its 

 attributes and conditions to the composition of its medium that there is the least 



