 The conclusion that natural populations in general, like that to which this study is devoted, are affected by selective action, varying from time to time in direction and intensity and of sufficient magnitude to cause fluctuating variations in all gene frequencies is in good accordance with other studies of observable frequencies in wild populations. … We do not think, however, that it has been sufficiently emphasized that this fact is fatal to the theory which ascribes particular evolutionary importance to such fluctuations in gene ratios as may occur by chance in very small isolated populations. …