Genetiska Institutionen Lunds Universitet Institute of Genetics University of Lund Lund, Sweden Lund, January 12, 1961. Dr. J. Lederberg Department of Genetics Stanford University Medical Center Palo Alto, California U.S.A. Dear Dr. Lederberg: Dr. L.L. Whyte published recently in Science (No. 3432, 7 October, 1960, pag. 954) an article which deals with the problem of selection. In this article he discusses a point of view based on evi- dence which I produced some years ago on the organization of the chromosome. Dr. Whyte is not aware of the recent developments in this field and has put forward some interesting views very similar to those which I expressed in two papers in 1954 and 1956. I thought it adequate to assemble in a short article the evidence available at present on this phenomenon, and to put forward my present views on the subject. Since Dr. Whyte’s article was published in Science it should be appropriate that mine would also appear in the same periodical. I would appreciate if you would read critically my paper and for- ward it to Dr. E.L. Tatum in case you find it suitable for public- ation in the journal. Sincerely yours, LP, Jorma te Frm A. Lima-de-Faria Associate Professor at the University of Lund