THE CHROMOSOMES IN HEREDITY

In a recent announcement of some results of a critical study of the chromosomes in the various cell-generations of Brac/zystola' the author briefly called attention to a possible relation between the phenomena there described and certain conclusions first drawn from observations on plant hydrids by Gregor Mendel in 2 1865, and recently confirmed by a Ilurliber of able investigators. Further attention has already beeti called to the theoretical aspects of the subject in a brief communication by Professor E. B. Wilson.3 The present paper is devoted to a more detailed discussion of these aspects, the speculative character of which may be justified by the attempt to indicate certain lines of work calculated to test the validity of the conclusions drawn. The general conceptions here advanced were evolved purely from cytological data, before the author had knowledge of the Mende han principles, and are now presented as the contribution of a cytologist who can make no pretensions to complete familiarity with the results of experimental studies on heredity. As will appear hereafter, they completely satisfy the conditions in typical Mendelian cases, and it seems that many of the known devia tions from the Mendelian type may be explained by easily con ceivable variations from the normal chromosomic processes. It has long been admitted that we must look to the organiza tion of the germ-cells for the ultimate determination of hereditary phenomena. Mendel fully appreciated this fact and even insti tuted special experiments to determine the nature of that organi zation. From them he drew the brilliant conclusion that, while,