The instinct of the young chick to seize in its beak any small moving object is a simple and useful reflex action, but if the object should happen to be a bee which stings the chick, another bee or similar insect will not be seized. Here we see that a reflex has been changed, and changed with amazing quickness. Moreover, the chick has learnt to associate this experience with a particular sort of moving object. It is this power to benefit by the result of a brief experience that is one of the most advantageous properties of the organism. Young chicks first show a drinking reflex if by chance their beaks are wet by water. At once the head is lifted up, and the drop of water passes down the throat. In this way the chick first learns the meaning of water, and no doubt soon comes to associate it with its own condition of thirst. The sight of water produces no effect on the inexperienced chick, and it may even stand with its feet in the water without drinking; but as soon as it touches, by chance, the water with its beak, the reflex, or rather the set of reflexes is started. A more complicated instinct is that shown by the spider in making its web. In some cases the young are born from eggs laid in the preceding summer, and can have had, therefore, no experience of what a web is like; and yet, when they come to build this wonderfully complex structure, they do so in a manner that is strictly characteristic of the species. The formation of the comb by bees, in which process, with a minimum of wax, they secure a maximum number of small storehouses in which to keep their honey and rear their young, is often cited as a remarkable case of adaptation. There has been some discussion as to whether birds build their nests in imitation of the nest in which they were reared, or whether they do so independently of any such experience. There can be no doubt, however, that in some birds neither memory nor imitation can play any important part in the result, and that they build their nests as instinctively as spiders make webs. These instincts of spiders, bees, and birds appear to be more complex than the reflexes and tropisms that were first described. Whether they are really so, or only combinations of simple responses, we do not yet know. That they have come suddenly into existence as we now find them does not seem probable, but this does not mean that they must have been slowly acquired as the result of selection. The mutation theory also assumes that the steps of advance may have been small. Our account may be concluded with the recital of some instincts, chosen almost at random, that serve to show some other adaptations which are the result of these inborn responses.