ASPECTS OF KINETIC EVOLUTION 1 99 



These suggestions have not been able to retain the full con- 

 fidence of biologists for the selective theory, as witness the 

 recent remarkable diversions towards Mendelism and muta- 

 tionism. The prompt acceptance of these doctrines by so many 

 students of evolution is not justified by any indication of general 

 pertinence for the facts on which they are based. They met 

 with immediate welcome because they afforded a suggestion, 

 at least, of methods by which new characters or character-com- 

 binations could be produced. They promised, in other words, 

 the long-needed supplement of the selective theory, the cogs 

 which selection might turn. 



The kinetic theory recognizes that evolution does not depend 

 upon selection nor upon the environment, and still less upon 

 mutation and Mendelism. The evolutionary causes are in the 

 species, not in the environments. They are resident, moreover, 

 in species as constituted in nature, and are exemplified only 

 abnormally in the phenomena which become prominent in the 

 close-bred domesticated plants to which the studies of Mendel 

 and De Vries were mostly directed. 



TWO TYPES OF ORGANIC FITNESS. 



The current belief in the environmental causation of evolution 

 is largely due to the confusion of two different kinds of organic 

 fitness, (i) The general fitness of the species for the environ- 

 ments in which they exist ; and (2) the special fitness or power 

 of adjustment of the individual organisms to particular condi- 

 tions which they may encounter. An interesting example of 

 the extent to which these two distinct phenomena have been 

 confused may be found in so well known a work of reference 

 as the Standard Dictionary. Adaptation is defined as "an ad- 

 vantageous conformation of an organism to changes in its envi- 

 ronments," but the quotation given to illustrate the use of the 

 word in this sense alludes to the " special adaptations " of deep- 

 sea organisms. The definition applies to the second type, fit- 

 ness by individual adjustment, while the example refers only to 

 the first type, the general fitness of the species, genus or family 

 as a whole. 



No method has been suggested whereby either type of fitness 

 Proc. Wash. Acad. Sci., December, 1906. 



