DEPARTMENT OF EXPERIMENTAL EVOLUTION.* 



C. B. Davenport, Director. 



Among the principal advances of the year have been the extension 

 of the series showdng the evolution of the chromosome complex of 

 Drosophila and allied flies (perhaps the strongest purely cytological 

 argument yet presented for the individualitj^ of the chromosomes); 

 the lack of dependence of the vigor of certain strains of parthenogenetic 

 Cladocera upon the recurrence of sexual reproduction; the discovery 

 that in different strains of Lychnis there is a difference in the dominance 

 of one and the same trait, hermaphroditism (including maleness) ; 

 the demonstration that in certain plant hybrids the characters whose 

 determiners are derived from both parental germ-plasms develop more 

 promptly than those whose determiners come from only one side of the 

 house; the demonstration of a triple factorial basis of the fohage color 

 of Lychnis, and of multiple determiners in the reduction of the number 

 of bristles in Drosophila; the working out of a theory of a pair of factors 

 (and their absence) that is capable of explaining the hereditary basis 

 of temperament; the demonstration that the symptoms of certain 

 diseases (Huntington's chorea, pellagra) are determined by several 

 hereditary factors — are, indeed, '' syndromes"; the demonstration 

 that hereditary brittle-bone (or osteopsathyrosis) is due to a dominant 

 factor; the production of a strain of beans with double the usual 

 number of cotyledons and "fu-st leaves" of the seedling; the preparation 

 for the press of one volume of the unpubhshed scientific work of the late 

 Professor Whitman. 



STAFF. 



The work of this Department during the present year has been 

 carried on by seven resident investigators and various associates and 

 assistants. The Director has, besides his other duties, put most of his 

 time on the analysis of the data of human inheritance, assisted by Miss 

 Mary T. Scudder. Dr. George H. Shull has used plant material for 

 his studies in heredity and has been assisted part of the time b}'^ Mr. 

 B. C. Helmick. Dr. J. A. Harris also has paid particular attention to 

 the inheritance of abnormalities in beans, with the assistance of the 

 Misses Lockwood and Margaret and Lillie Gavin. 



Mr. Charles W. Metz is making studies on the subject of the mecha- 

 nism of heredity and has been temporarily assisted by Mr. H. H. Plough. 

 Dr. Oscar Riddle has worked on the chemical distinctions that lie at 

 the basis of sex, with the assistance of Miss Adelaide Spohn and, later, 

 of Mr. O. R. Clutter. 



♦Situated at Cold Spring Harbor, Long Island, New York. 



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