57 BIOLOGY 



Pringsheim, H. Die Variabilitat niederer Organismen. 



Berl. 1910. 



Vernon, H. M. Variation in animals and plants. 



Lond. 1903. 



Vries, H. de. Mutation theory. 2 vols. 



Lond. 1910-11. 



'575 2 Species and varieties. Chicago 1905. 



'575 2 Shull, G. H. Bursa bursa-pastoris and Bursa heegeri, 

 : 583123 biotypes and hybrids. Wash. 1909. 



'575 2 Stout, A. B. Establishment of varieties in Coleus. 

 : 583891 Wash. 1915. 



'575 2 Pearl, R. Variation in Ceratophyllum. W'ash. 1907. 



: 583987 



*575 2 Crampton, H. E. Studies on the variation, distribu- 



: 5943 tion, and evolution of the genus Partula. The 



species inhabiting Tahiti. Wash. 1916. 



5752 Lutz, F. E. Variations of certain characters of Gryllus. 

 159572 Wash. 1908. 



5752 Pearl R., and Clawson, A. B. Variation in the cray- 

 : 597 fish. Wash. 1907. 



5753 ENVIRONMENT. 



5753 Henderson, L. J. Fitness of the environment. 



New York 1913. 



5753 Semper, K. Natural conditions of existence as they 

 affect animal life. Lond. 1881. 



5754 NATURAL SELECTION. 



5754 Coe, C. C. Nature versus natural selection. Lond. 1895. 

 5754 Sturtevant, A. H. An Analysis of the effects of selec- 

 tion. Wash. 1918. 



'5754 Wallace, A. R. Darwinism : an exposition of the theory 

 of natural selection. Lond. 1889. 



'5754 Natural selection and tropical nature. Lond. 1891. 



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