Abstract
(1) Description is given of the occurrence of the following types of chromosome reorganization observed in meiosis of, second and third generation progenies derived from treatment of Nicotiana tabacum with x-rays and radium: attachment, translocation, deletion, fragmentation, altered valency.
(2) Attention is called to the relatively high degree of viability of these types of chromosome alteration as, they occur in N. tabacum.
(3) Evidence is presented that stable derivatives, often.distinct in external morphology from the original race, may in certain organisms be products of these chromosome reorganization and provide material of interest both from the experimental and from the practical point of view.
