In this same connection, we may note that the aesthetic appreciation among the birds appears to have attained a far higher level than it has won in any other creatures. There can be little doubt that the exquisitely beautiful plumage, the unparalleled shapeliness of form and grace of carriage, as well as the melodies which are uttered by so many species, all owe their development to a process of sexual selection which has led the discerning females to prefer the more ornamental of the males who sought them as partners. If any one will examine the exquisite shapes and gradations of color which are exhibited in the tail of the peacock, or of the lyre-bird, or even the coloration of the game-cock, he may perhaps imagine how prodigious must be the development of the aesthetic sense in these species, in order that it may take account of every little betterment which leads towards more perfect beauty. As it will take the generations of aesthetes many generations before they are able to "live up to" the level of their culture which is attained by the peacock's tail, it is not unreasonable for us to hold that in the appreciation of simple beauty in form and in color, the birds are far ahead of ourselves. It must not be supposed that our aesthetic culture is to be reckoned below that of birds, though in our case the work embodies the delineation of ideas, while in the birds it is a matter of pure ornament. Nevertheless, taking the evidence which shows the way in which these creatures appreciate beauty in the three realms of form, color, and sound, it seems to me clear that while their intellectual life is low, their purely emotional experiences are probably more vivid than those of ordinary men. As the joy of life is, in the main, even in ourselves the result of emotional experiences, we may fairly reckon, even on _a priori_ ground, that the birds win a measure of happiness, though it be that of an unconscious kind, which is granted to no other living beings. Psychologically described, they might well be termed the group built for joy. Their bodies are, on the whole, the best constructed of all animals, except the insects. They suffer little from disease. We all see that their intercourse with each other is freer and merrier than that of other creatures. The wide range of their notes shows that in most forms they appreciate every little difference in the pleasure-giving changes of the day or the weather. They rejoice in the coming of each morning; they are sorrowful with the advent of each evening. They echo the distress of their kind in a readier way than any other forms. He is indeed a poor naturalist who overlooks this trait; for however deeply he may have delved, he has not won the jewel unless he appreciates this element of an unending joy which the bird-life continually offers him. From that life we may well believe that man is hereafter to derive some great and fruitful lessons. USEFUL INSECTS