THE London Scientific Film Society gave a demonstration of films on May 16 at the Imperial Institute cinema. Dr. Julian Huxley introduced the film “Galapagos” and led a discussion on it afterwards. The film was made by the Dart-ington Hall Film Unit under the direction of Mr. William Hunter and Mr. David Lack and was photographed by Mr. Richard Leacock. It illustrates the comparatively free adaptive evolution of new types, in absence of competition, from original single colonizations on a group of oceanic islands. The extent of the differences from the mainland forms depends on the time that elapses since the colonization. In such cases, where the pressure of natural selection is light, the animals are not as well equipped to fill their environmental niches as are mainland forms. For example, there is a member of the gull tribe, the close ancestors of which are water birds, which nests in the trees although it still retains webbed feet ; and the finches have evolved a range of species to exploit the available food supplies, although the shape of their beak, unlike those of most mainland birds, does not always give a precise indication of the food habits of the bird.