THE THEORY OF TITTLEBATS. 827 



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 pecul- 

 iarities 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 orna- 

 ments 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 dis- 

 appear 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 metal- 

 lic throat-pouches. It is at such times alone that the face of the man- 

 drill glows with blue and purple, or that the rhe'sus monkey blushes a 

 vivid crimson. Thi*oughout the whole of nature, in fact, all the most 

 beautiful animals attain their highest beauty in the season of court- 

 ship, 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 ; 



