THE recent exchange between Woolhouse1 and Popper2 presents the enigma of the low entropy content of living systems. The means whereby their rapid decay into the inert state of “equilibrium” is avoided are serious problems to the theoretical biologist. It is, of course, to Schrodinger3 that we owe the classic analysis of biological entropy. It was the source of negentropy which Schrodinger was unable to discover, as the recent discussion indicates. That from, one generation to the next, a complex coding and decoding can occur without net loss of negentropy is problem enough, but in the large sequence of generations through geological time, we see that, if anything, the informational system becomes fuller and the organization of many species more improbable. It is my purpose here to show what I believe to be the answer to this seeming paradox and to describe the “entropy pump” whereby the species of living matter not only prevent a drop into a position of greater positive entropy at each generation, but may in fact acquire more negentropy as their reproduction continues. This will involve only principles widely known and easily defended.