In early time, before the invention of the railway and telegraph, some ingenious breeder of pigeons, observing the constant way in which these creatures returned to the place where they were bred, invented the plan of using them to convey information. This service was found convenient not only for ordinary correspondence, but was exceedingly valuable where a place was beleaguered by an enemy. In such cases carrier pigeons could often be used to convey information across the otherwise impassable lines. Even in modern times, as, for instance, during the last siege of Paris, these swift and sure flying birds proved of great use in keeping up communications between the people of the invested town and the French armies in the field. Letters in cipher, sometimes photographed down until the characters were microscopically fine, were made into packages of small weight in order not to impede the flight of the bird, carefully affixed to its body, and thus sent away. Very generally these curious shipments came to the hands of those for whom they were destined. The birds can be trusted to fly at night; they retain for a long time the memory of their home, and spare no pains to return to it. The homing power of the carrier pigeon appears to be a special development of a natural capacity, as is also its swiftness and endurance in flight. Our other breeds and the wild species whence they have all come are not disposed to undertake long journeys; they rarely, indeed, wander far from their abiding places. Our experience with the carriers shows how readily the creatures may be educated to perform feats which they were not accustomed to do in their wild state. Something of the same elasticity of constitution may be observed in the bodies of our pigeons as they have been affected by selection. Not only has the plumage been greatly altered by the breeder's art and in pursuance of his plans, but the form and proportions of the bones have coincidently and unintentionally been greatly changed. So considerable are these alterations that if these creatures were submitted for dissection to a naturalist who knew nothing of the history of the bird, he would have no hesitation in classing them as belonging not only in different species, but as members of diverse genera. It must be regarded as unfortunate that the experiments which have been made on pigeons have been limited to their features of form, color, and slight peculiarities in their habits. If the breeders had sought to modify the intellectual parts with anything like the insistence which they have given to the development of these bodily peculiarities, we might now have a most valuable store of knowledge as to the limitations of animal minds. The facts gained in the breeding of the carriers show clearly that certain of the instincts of these birds can be readily modified. There is every reason to suppose that their mental capacities in other directions have something of the same pliability.