I will begin with one of the best-known habits of the stickleback, its nest-building instinct; because that is really the one of its peculiarities which most affects the theory of tittlebats, and has the deepest interest and the widest implications for the general reader.
If you put a pair of assorted sticklebacks into a small aquarium, and supply them well with food during the early spring, you will find that after a short time the male fish begins to undergo a remarkable change of personal appearance. His coloration grows brighter and more beautiful; his throat and belly assume a deep crimson hue; his eyes acquire a brilliant bluish-green metallic luster, like the gorget of a humming-bird; and in the well-chosen words of his panegyrist, Mr. Warington, his whole body becomes almost translucent, and seems to glow as with some mysterious internal brightness. It is the season of courtship, and the stickleback is adorning himself in his courting suit.
"In the spring a ruddier crimson comes upon the robin's breast,
In the spring the wanton lapwing gets himself another crest,
In the spring a livelier iris changes on the burnished dove,
In the spring a young man's fancy lightly turns to thoughts of love."
The name of the stickleback falls unfortunately below the level of the lyrical muse, or else he might perhaps form a fifth member in that lovers' quartet. For no creature decks himself out in more gorgeous nuptial colors, or arrays himself more like Solomon in all his glory against his wedding-day, than the common little Hampstead tittlebat of Mr. Pickwick's missing dissertation.
Theoretically, of course (and we are all on the theory of tittlebats here), this assumption by the stickleback of special colors and ornaments for the pairing-season is all of a piece with the numerous other devices of Nature for securing the due selection by animals of the handsomest, strongest, and most vigorous mates. Many of the more brilliant animals don their finest decorations for the period of courtship only. The crests and lappets of the herons and egrets are developed and retained during the summer alone; they fall off as soon as winter arrives. The African widow-birds deck themselves out in the nesting-season with very long and conspicuous plumes, which disappear again, and leave them as mere inconspicuous little brown birds, after the brood is reared. The crested newt puts on his vandyked head-gear, and dapples his body with orange and crimson spots, at the approach of spring-tide. The speckled trout becomes livelier in hue; the salmon shine with brighter silver; the lizards acquire their metallic throat-pouches. It is at such times alone that the face of the mandrill glows with blue and purple, or that the rhesus monkey blushes a vivid crimson. Throughout the whole of nature, in fact, all the most beautiful animals attain their highest beauty in the season of courtship, and many which are never beautiful at other times then put on the most decorative ornaments or the most gorgeous coloring. This is true alike of the wings of butterflies, and of the song of crickets;
