The function of the light-ether, the second of the four modes of ether, can best be envisaged by thinking of the difference between a plant growing in darkness (perhaps a potato sprouting in a cellar) and another of the same species exposed to the influence of the light. On Plates VII and VIII two kinds of unicellular organisms are shown, of one which – the green algae – is accustomed to live in light, the other – the bacilli – in darkness. These things are, of course, well-known facts. Our purpose here, however, is not merely to record them as ‘fact’, but, by re-creating them within ourselves, to use them to gain an experience of the function of the light-ether.