326 CARNEGIE INSTITUTION OF WASHINGTON. 



proper list of subjects and cross-references to orient the reader as to the 

 location of titles, it is believed that this will be a labor-saving device 

 and that it will simplify many of the bibliographic problems which have 

 perplexed both the editor and the readers. 



In connection with increased literature on various subjects, the intro- 

 duction of such new titles as "Entomology," ''Medical Sociology," 

 "Encephalitis lethargica," "Food Economics," "War Bread," etc., is 

 self-explanatory. 



BIOLOGY. 



Castle, W. E., Harvard University, Cambridge, Massachusetts. Continua- 

 tion of experimental studies of heredity in small mammals. (For previous 

 reports see Year Books Nos. 3-18.) 



The subjects under investigation during the past year have been 

 substantially the same as in the previous year, viz: (1) a study of 

 linkage, which causes characters either to go together or to stay apart 

 in heredity, and (2) a further study of size inheritance. 



Progress has been made in determining more precisely the linkage 

 relations in rats of three genes which occur in a conunon linkage system. 

 It has been found that the arrangement is probably linear. A large 

 stock of animals has been reared for the purpose of gaining a decisive 

 answer to this question. A convenient and accurate method of de- 

 scribing linkage strength has been devised. The linkage strength of 

 two linked genes of mice has been determined. A pair of linked genes 

 has been discovered in rabbits. The characters involved are English 

 pattern of white spotting and dilution. The indicated linkage strength 

 is 23 on a scale of 100. Dr. L. C. Dunn, who has been associated with 

 these investigations for several years, took up the work of biologist at 

 the Storrs (Connecticut) Agricultural Experiment Station in March. 

 The results of his investigations with mice will shortly be published. 

 Material for a study of size inlieritance in rabbits has been accumulated 

 during the past three years and is now being studied. It is hoped that 

 the results will be ready for publication within a few months. A con- 

 siderable part of the work conducted during the past 17 years under the 

 auspices of the Institution will be summarized or reviewed in a second 

 edition, now in press, of "Genetics and Eugenics." Four short papers 

 have been published during the year. 



Mann, Albert, Washington, District of Columbia. Continuation of investi- 

 gations and preparations for publication of results of work on DiatomacecB. 

 (For previous report see Year Book No. 18.) 



The large number of requests for information and for cooperative 

 study of the diatoms during this first year of research has exceeded the 

 resources of the office. This has been partly due to the fact that the 

 writer, although well supplied with laboratory help, has so far been 



