290 CARNEGIE INSTITUTION OF WASHINGTON. 



Medical Association, the Boston Medical Library, and the New York 

 Academy of Medicine a fair proportion of the German literature, in 

 particular that in the weekly medical periodicals, has been indexed up 

 to the end of 1916. The literature subsequent to this date will prob- 

 ably not be accessible until after the conclusion of the war. Apart 

 from Germany, the only foreign nations which have kept up their 

 full quota of medical Uterature are France, Italy, Spain, the Scan- 

 dinavian and Spanish- American countries. The falling off of this 

 material in England is evidenced by the fact that the British Medical 

 Journal for the first half of 1917 contains 896 pages as against 1,440, 

 1,104, and 904 pages for the corresponding semesters of 1914, 1915, and 

 1916 respectively. A soUtary Belgian journal, the Archives medicales 

 beiges, has been revived during the present year. The preponderance 

 of war literature in the foreign periodicals is everywhere manifest. 



BIOLOGY. 



Morgan, T. H., Columbia University, New York. Study of the constitution 

 of the germ-plasm in relation to heredity. (For previous report see Year 

 Book No. 15.) 



The program outlined in the application for the grant has been car- 

 ried nearly to completion. The linkage relations of the genes of 

 chromosomes II and III have been studied. The results for the second 

 linkage group will be ready for publication this autumn; most of the 

 data have been collected for the third linkage group and will be brought 

 together in the course of the winter. Since publishing the report on 

 the first or X chromosome (Carnegie Publication No. 237) much addi- 

 tional information on the location of as many more new sex-linked 

 mutations has been collected. 



The locahzation of the genes under '"normal" conditions is only a 

 part of the program followed, for in all three of these chromosomes 

 inherited linkage variations have been discovered and studied. In 

 addition to the inherited variations, evidence of the influence of external 

 conditions upon linkage has been obtained by Dr. H. H. Plough, work- 

 ing as a collaborator. The possibiUty of differences in linkage rela- 

 tions existing in wild stocks from widely separated localities has also 

 been looked into by another co-worker, Mr. A. M. Brown. A detailed 

 biometrical study of crossing over has been carried on in the laboratory 

 by Mr. J. W. Gowen; and an investigation of the relation between one 

 crossover and a second in the same chromosome (coincidence) has been 

 made by Dr. Alexander Weinstein. 



In addition to these studies concerned directly with linkage, Miss 

 Clara J. Lynch has carried on an investigation of certain unusual phe- 

 nomena relating to fertihty, and Miss Mary B. Stark has made a study of 

 a sex-linked tumor that kills half the males in each generation. The 

 researches of these six co-workers, while not subsidized by the grant of 



