Many of the Snails, like _Helix nemoralis_, are gaily coloured. Are these hues, these bands of black and yellow, the product of “sexual selection”—the outcome of a process of selection from among the most conspicuously coloured individuals as postulated by the Darwinian theory of Sexual Selection? If so, then this choice must be regarded as a periodic recurrence coinciding with the period during which the individual is dominated by its female attributes. In due course it becomes, for the time, a male, and may find itself rejected, owing to a lack of intensity in its coloration, or, on the other hand, it may vanquish a rival by its very splendour. Each, in short, would help materially in this process of beautification. If the choice of mating for it is this rather than a choice of mates—proceeds on these lines, the bright coloration of the members of this species becomes easy to understand. But does it? It is more than doubtful whether the eyes of Snails are sufficiently good to distinguish the coloration of their neighbours’ shells, or for the matter of that of their own, for their eyes being carried on long mobile stalks, they should have no difficulty in contemplating their own charms. And what of Snails of more sober hues? It seems highly probable that here, as in so many cases, scent is the selecting factor, and the coloration is an “accidental” feature. That the colour of the shell plays no such part as that just postulated may be gathered from the evidence afforded by many marine species, whose shells, though conspicuously marked, are, during life, completely enveloped and concealed by the all-investing, fleshy mantle. In like manner the exquisite beauty in the form and sculpturing of the shell which so many species exhibit, are characters which cannot be regarded as due to sexual selection. As touching the danger of self-fertilization to which reference has been made. That this is real is shown by the fact that the ova and spermatozoa are rarely ripe in one individual at the same time. However, among the pulmonata, or air-breathing gastropods, it seems to have been established that self-fertilization can, and does, occur. That in some species, at any rate, where cross-fertilization, for some reason, is impossible, the individual thus isolated can store up its own spermatozoa to be used in fertilizing its own eggs. But the fact that this rarely happens is testimony enough that such occurrences are inimical to well-being.