DR. BATHER'S lecture on “Evolution through Adaptation”, printed in NATURE of Mar. 30, bristles with debateable points, but I will select a cardinal one which appears to present a fundamental difficulty in his theory. He speaks of the changes of depth and salinity in the waters which have taken place in geological time and draws the conclusion “that the surroundings of a race are continuously altering; the race has perpetually to catch up with the change”. But even if the small changes that have taken place in the oceanic environment could account for the trend of evolution, for example, from an Asteroid to an Echinoid form in the Echinodermata, how could be explained the persistence of the original Asteroid type practically unchanged? The race has not changed, if certain members or groups of it have.