It is among the vertebrate forms alone that we find animals which by their characteristics of body or of mind are well fitted to have an economic or social value. There alone are the qualities of flesh or of the external covering such as to make them in a high measure valuable, and the instincts of a nature to fit them for association in man's work. Even among these back-boned animals we find that the lower groups--the fishes, the amphibians, and the reptiles--promise little in the way of gains as compared with the higher groups, the birds and mammals; yet even among these inferior creatures we find certain forms which give promise of improvement under the care of man. Some of the fishes readily learn to come to any one from whom they may expect food, and they indicate in other ways that they are capable of a certain intellectual advance. The frogs and toads readily learn to recognize a master. Several of the larger members of the first-named forms could advantageously be bred so as to be very useful as food. The common hop toad of our gardens is an admirable helper in restraining the excessive development of certain slugs and insects. The tortoises and turtles contain a number of species which are edible, and many of the forms invite the breeder's care. It is, however, when we ascend in the type of vertebrates to the level of the birds that we find the great array of creatures which are worth considering as members of our civilization. Nearly all the birds except those of prey and those which haunt the seas can easily be accustomed to man. A few of these species which have been reduced to captivity have not become sufficiently reconciled to the unnatural conditions to maintain their breeding habits. Even in these cases, however, it seems likely that in spacious aviaries, at least in climates to which they are accustomed, it will be possible to secure the continuous reproduction of the kind, on which all development by the breeder's art depends.