90 REPORTS OF INVESTIGATIONS AND PROJECTS. 



In connection with Airs. Davenport I have begun a series of studies into 

 normal human inheritance. A paper on inheritance of human eye-color was 

 published last autumn (Science, Nov. i, 1907), in which it was shown that 

 blue-eyed parents can have only blue-eyed children, but that if either parent 

 has brown eyes the children may be also of that type. With these results the 

 work of C. C. Hurst, of England, published this spring, is in full accord. In 

 May we published in the American Naturalist results of our studies on the 

 inheritance of the form of the hair, proving that two straight-haired parents 

 have only straight-haired children, but that if either parent is curly-haired at 

 least some of the children may be of that type also. The results of studies on 

 hair-color — a very complex subject — are nearly ready for publication and 

 show that the amount of black pigment in the children does not ordinarily 

 exceed that of the darker parent. Much additional data is at hand and will 

 be reduced as fast as possible. The practical importance of the proof of the 

 application of the modernized Mendelian law of inheritance to man is that it 

 enables us to predict the marriage matings that may be expected to yield a 

 particular type of offspring. If we have hitherto made little progress in 

 eugenics it is because there has been little precise knowledge as to the result 

 of any mating. When such knowledge has been gained and formulated we 

 may expect educated persons to take advantage of it. 



Our generalization that the quality of a character tends to rise in the off- 

 spring to no higher a grade than in the parent helps account for the facts of 

 the frequent injurious effects of continued inbreeding. If in both parents any 

 organ stands at a low level it will stand at that level or lower in the children ; 

 if relatives, with the diminished grade, be again inbred the organ drops to a 

 still lower grade or may in time disappear altogether. Of the injurious ef- 

 fects of inbreeding Dr. Shull has again brought evidence in the case of corn ; 

 there is evidence in poultry; even in the vinegar-flies (Drosophila) Dr. Lutz 

 has clear evidence of degeneration of the wings ; and in our human records we 

 have cases of albinism, imperfect sense-organs, and low intelligence. In ac- 

 cordance with this generalization qualities tend to run downhill unless lifted 

 by union with a quality of higher grade — here we see the advantage of out- 

 crossing in strengthening the stream of germ-plasm. 



DETAILED REPORTS ON SCIENTIFIC WORK. 

 HEREDITY. 



Poultry. — In this work 59 pens were maintained. About 12,000 eggs were 

 incubated and 3,546 chicks hatched. As a matter of some physiological inter- 

 est may be given the weekly record of egg-laying, in 4-weekly periods, of the 

 350 to 320 hens that constituted our flock. 



For 4-week period beginning — 



Sept. I 546 Jan. 19 863 June 7 650 



" 29 309 Feb. 16 2,556 Julys 253 



Oct. 27 190 Mar. IS 3,736 Aug. 2 223 



Nov. 24 299 Apr. 12 4,261 . 



Dec. 22 284 May 10 3,082 Total 17,252 



