20 Carnegie: institution of Washington. 



logic time. From this work it is believed that some of the salient fluctua- 

 tions in climate during the past two or three thousand years may be clearly 

 made out. Another noteworthy investigation of the year is that of the respi- 

 ration of cacti, undertaken by Prof. H. M. Richards in collaboration with the 

 department. This has developed the remarkable fact of a definite diurnal 

 periodicity in the acid content of the sap of the cacti under observation. The 

 progress and status of many other instructive investigations are set forth at 

 length under the twenty subdivisions of the Director's report, to be found in 

 full in the current Year Book. From this it appears that, in addition to the 

 regular and associate members of the staff of the department, about an equal 

 number of individual investigators have collaborated in the researches under 

 way. Special attention may be here invited to the detailed account given in 

 one of the subdivisions of this report by Professor Tower in reference to his 

 further experiments on the evolution of chrysomelid beetles, the results of 

 his early work in this line under the auspices of the Institution having been 

 issued as publication No. 48. 



It is a well-known fact that important generalizations in science usually 



leave a multitude of details to be worked out. Indeed, advances often raise 



_, more questions than they settle. Such has been the won- 



L/epartment . 



of Experimental dcrfully fruitful effect of the doctrine of evolution pro- 

 Evolution, pounded by Darwin, Spencer, and Wallace a half century 

 ago. It should not be surprising, therefore, that the program of the Depart- 

 ment of Experimental Evolution presents a considerable variety of investi- 

 gations related to the highly complex problem of heredity chosen by the 

 Director as the principal object of research. Thus the work of the year 

 includes investigations of heredity in plants, insects, birds, animals, and man. 



One of the most promising investigations of the year is that of the Direc- 

 tor in reference to the heredity of epileptics. Through his connection with 

 the Eugenics Record Office, he has collaborated with Dr. David F. Weeks, 

 of the New Jersey State Village of Epileptics, and secured a large quantity of 

 accurate statistical data bearing directly on this disorder. From these data 

 it appears not improbable that important practical deductions may be pres- 

 ently, if not already, drawn. Another investigation continued during the 

 year, which involves prime utilitarian application, is that of Dr. Shull on the 

 effects of self-fertilization in maize, or Indian corn. His earlier conclusions, 

 published in 1908, have been confirmed by the later studies. A striking result 

 from the latter is that, other conditions being the same, the yield of cross- 

 fertilized plants proved fifty per cent greater than that of the self-fertilized 

 plants. Observational and experimental work has been carried on also along 

 many other lines. The total number of zoological individuals under study 

 exceeded 2,000, while the range of plants observed included nearly 500 spe- 

 cies and upwards of 40,000 individuals. 



