220 ANNUAL REPORT SMITHSONIAN INSTITUllON, 193 4 



number present in somatic cells was almost as brilliant an example 

 of scientific prophecy as was the prediction of the existence and 

 position of the planet Neptune. And, finally, his explanation of the 

 origin of fitness in the living world is still, I think, the best scientific 

 conception that has ever yet been offered. I cannot better express 

 my own views on this subject than by closing with these words from 

 the preface of his last book (1902) : 



Although I may have erred in many single questions which the future will 

 have to determine, in the foundation of my ideas I have certainly not erred. 

 The selection principle controls in fact all categories of life units. It does not 

 create the primary variations but it does determine the paths of development 

 which these follow from beginning to end, and therewith all differentiations, 

 all advances of organization, and finally the general course of development of 

 organisms on our earth, for everything in the living world rests on adaptations. 



LITERATURE CITED 



In general only the earliest in a series of papers, or a later one which pre- 

 sents a general summary, is cited. 

 Bailey, Ij. H. 



1896. The survival of the unlike. Proc. Amer. Philos. Soc, vol. 35. 

 Bateson, W. 



1894. Materials for the study of variation : Discontinuity in tlie origin 

 of species. London. 

 Blakeslee, a. F. 



1921. Types of mutations and their possible significance in evolution. 

 Amer. Nat., vol. 55, pp. 254-267. 

 Blakeslee, A. F., and Aveuy, B. T., Jr. 



1919. Mutations in the jimpson weed. Journ. Heredity, vol. 10, pp. 111- 

 120. 

 Clausen, R. E. 



1928. Interspecific hybridization in Nicotiana, VII. Univ. Calif. Pubs, 

 in Bot., vol. 11, pp. 177-211. 

 Clausen, R. E. and Goodspeed, T. H. 



1925. Interspecific hybridization in Nicotiana, II. Genetics, vol. 10, pp. 

 278-284. 



CONKON, E. G. 



1896. The factors of organic evolution from the embryological standpoint. 



Proc. Amer. Philos. Soc., vol. 35, pp. 78-88. 

 1921. Problems of organic adaptation. Rice Inst. Pamphlet, vol. 8, pp. 299- 

 3S0. 

 Cope, E. D. 



1896. The primary factors of organic evolution. Chicago. 



CUENOT, L. C. 



1911. La genese des especes animales. Paris. 

 De Vuies, H. 



1901, 1903. Die Mutationstlieorie. Leii^zig. 

 Fisher, R. A. 



1930. Tl*e genetical theory of natural selection. Oxford. 

 Galton, F. 



1892. Hereditary genius, 2d ed. London. 



