DEPARTMENT OF GENETICS.* 



C. B. Davenport, Director. 



GENERAL STATEMENT. 



The organization of the Department of Genetics consoHdates and 

 unifies the work of eugenics and experimental evolution and places 

 an institution for the study of human heredity and reproduction in 

 the same organization with one for the experimental breeding of other 

 mammals, animals, and plants. It is believed that the combination 

 will be peculiarly advantageous for fruitful research; a profound 

 biological investigation of mankind and his biotypes, their variations 

 of form and behavior and their genetical significance, has not hitherto 

 been carried out. 



Of the work of this Department during the past year, may first be 

 mentioned the researches that are demonstrating the close relationship 

 between variations in chromosome number and specific variations in 

 the form and other qualities of the body. The work on Datura 

 stramonium is offering remarkable explanations of the complexities of 

 de Vriesian mutation, a form of mutation of possibly not less general 

 significance than Mendelian mutation. While research has not yet 

 put "the mind into the chromosome," it seems not improbable that 

 some mental ''sports" in man, that deviate widely from the typical 

 condition, may some day be found due to such abnormalities in the 

 chromosome complex as are now known to characterize striking forms 

 of Datura. Attention is called to the discovery (page 132) that the 

 hybrids between two forms of domestic mice (one active and the other 

 slow) are on the average more active, sturdy, and intelligent than 

 either parental race. This is a quantitative result based on painstak- 

 ing measurement of nearly 300 individuals. 



Another matter of great theoretical as well as practical importance 

 is the demonstration that in mice there are hereditary physiological 

 factors that render certain strains and their hybrid descendants sus- 

 ceptible to the growth of tumors. In the absence of these factors 

 inoculated tumors will not grow. Moreover, the genetic nature of 

 these factors of susceptibility varies in different strains. Hitherto 

 our strains of mice have shown a complex genetic constitution, in that 

 probably four factors were required to determine susceptibility. Dur- 

 ing the current year it has been demonstrated that in one strain of mice 

 the combination of two factors, merely, is required for susceptibility. 

 In this strain the Mendelian nature of inheritance of susceptibility 

 to inoculated cancer is so simple as to be easily demonstrated to the 

 most skeptical. The discovery of the hereditary factors in inoculable 

 cancers constitutes obviously one of the most important advances in 

 cancer research. 



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



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