ASPECTS OF KINETIC EVOLUTION 333 



HEREDITY AS A RESULT OF ENVIRONMENT. 



The strength of the predisposition toward theories of environ- 

 mental causes of evolution finds many illustrations in the con- 

 troversies which have raged about the Lamarckian doctrine of 

 direct environmental influences. Thus Professor Lankester, 

 even when opposing Lamarck, assumes environmental influ- 

 ences of a character which the facts may not justify. It is shown 

 that Lamarck was illogical in supposing that new environmental 

 characters could be preserved by heredity and thus replace at 

 once the effects of the " long-continued response to the earlier 

 normal specific conditions," but it becomes evident, even while 

 this excellent chronological distinction is being drawn, that it 

 rests on a conception of heredity only slightly less objectionable 

 than that of Lamarck himself. Though making no direct ref- 

 erence to mechanical theories of heredity, these assumptions are 

 such as to suggest and to justify such interpretations. 



" Normal conditions of environment have for many thousands 

 of generations moulded the individuals of a given species of 

 organism, and determined as each individual developed and 

 grew ' responsive ' quantities in its parts (characters) ; yet, as 

 Lamarck tells us, and as we know, there is in every individual 

 born a potentiality which has not been extinguished. Change 

 the normal conditions of the species in the case of a young indi- 

 vidual taken to-day from the site where for thousands of gener- 

 ations its ancestors have responded in a perfectly defined way 

 to the normal and defined conditions of environment, reduce the 

 daily or seasonal amount of solar radiation to which the indi- 

 vidual is exposed ; or remove the aqueous vapor from the atmos- 

 phere ; or alter the chemical composition of the pabulum access- 

 ible ; or force the individual to previously unaccustomed muscular 

 effort or to new pressures and strains ; and (as Lamarck bids us 

 observe), in spite of all the long-continued response to the ear- 

 lier normal specific conditions, the innate congenital potentiality 

 shows itself. The individual under the new quantities of envir- 

 oning agencies shows new responsive quantities in those parts 

 of its structure concerned, new or acquired characters." 1 



lankester, E. Ray, 1906. Inaugural Address before the British Association 

 for the Advancement of Science. Nature, 74 : 330. Science, N. S., 24 : 607. 



