will produce a worm; and besides, she herself will be dead long before the unknown worm can be in existence. Therefore she works blindly; without knowing that her work is to subserve any useful purpose, she works to a purpose both definite and important; and her acts are uniform with those of all solitary wasps that have lived before her or that will live after her; so that we are compelled to refer these untaught actions to some constant impulse connected with the special organization of the wasp,--an innate tact, uniform throughout the species, of which we, not possessing anything of the kind, can form only a poor conception, but which we call instinct. There have been some philosophers, however, who have exercised their ingenuity in tracing so-called instinctive actions to the operation of experience. The celebrated Doctor Erasmus Darwin gave, as an illustration of this view, his opinion that the young of animals know how to swallow from their experience of swallowing _in utero_. Without going into any refutation of this position, we would only remark, in passing, that the act of swallowing is not an instinctive action at all, but a purely mechanical one. Would not Doctor Darwin have rejoiced greatly, if he could have brought to the support of his theory the observation of our own great naturalist, Agassiz, who, knowing the savage snap of one of the large, full-grown Testudinata, is said to have asserted, that, under the microscope, he has seen the juvenile turtle snapping precociously _in embryo_? But not only is instinct prior to all experience, it is even superior to it, and often leads animals to disregard it,--the spontaneous impulse which Nature has given them being their best guide. The carrier-pigeon or the bird of passage, taken a long distance from home by a circuitous route, trusting to this "pilot-sense," flies back in a straight course; and the hound takes the shortest way home through fields where he has never previously set foot. The existence of instinct prior to all experience or instruction, and its perfection in the beginning, render cultivation and improvement not only unnecessary, but impossible. As it is with the individual, so it is with the race. One generation of the irrational tribes does not improve upon the preceding or educate its successor. The web which you watched the spider weaving in your open window last summer, carefully measuring off each radius of her wheel and each circular mesh by one of her legs, was just such a web as the spider wove of old when she was pronounced to be "little upon the earth, yet exceeding wise."