Why should the gene be suggested to be inconstant when the contrary view, that gene structure is invariant except through mutagenic processes induced by potent external factors, has long been a universal doctrine of genetics? Indeed, during the early part of the present century before mutation was recognized as being of general occurrence, the seeming unvarying nature of the gene led to skepticism regarding the validity of the evolutionary theory; only later could the origins of the morphological differences between individuals and species be attributed to a combination of mutation and evolution, involving natural forces selecting between favorable and unfavorable genetic changes. But during the past several decades, as knowledge of the macromolecular constitution of or­ ganisms has increased to the point where even the primary structures of the genes themselves are being revealed on a routine basis, it has become increasingly difficult to ascribe all the resulting observations to ordinary mutagenesis and natural selection. Some more profound mechanism often seems to be present that influences both the constancy and inconstancy of the genes, an ap­ paratus whose existence this study hopes to reveal. In seeking to demonstrate the universality of this mechanism, data are sought through the numerous activities of organisms of many types wherever gene action changes are manifest.