at which bee-blossoms altogether cease to grow. Now, the butterfly differs greatly from the bee in his mode of honey-hunting; he does not bustle about in a business-like manner from one buttercup or dead-nettle to its nearest fellow; but he flits joyously, like a sauntering straggler that he is, from a great patch of colour here to another great patch at a distance, whose gleam happens to strike his roving eye by its size and brilliancy. Hence, as that indefatigable observer, Dr. Hermann Müller, has noticed, all Alpine or hill-top flowers have very large and conspicuous blossoms, generally grouped together in big clusters so as to catch a passing glance of the butterfly's eye. As soon as the insect spies such a cluster, the colour seems to act as a stimulant to his broad wings, just as the candle-light does to those of his cousin the moth. Off he sails at once, as if by automatic action, towards the distant patch, and there both robs the plant of its honey and at the same time carries to it on his legs and head fertilising pollen from the last of its congeners which he favoured with a call. For of course both bees and butterflies stick on the whole to a single species at a time; or else the flowers would only get uselessly hybridised instead of being impregnated with pollen from other plants of their own kind. For this purpose it is that most plants lay themselves out to secure the attention of only two or three varieties among their insect allies, while they make their nectaries either too deep or too shallow for the convenience of all other kinds. Nature, though eager for cross-fertilisation, abhors 'miscegenation' with all the bitterness of an American politician.