Hudson, in his interesting book, “The Naturalist in La Plata,” has also criticized Darwin’s theory of sexual selection. He has brought together a considerable number of interesting observations that go to show that the displays--dancing, singing, and combats--of males and females have no relation to mating. Many of them involve birds already mated, sometimes several males participating, sometimes males and females together. Some of the tourneys he describes are more elaborate than the mating instincts themselves, yet are not concerned with mating. He attempts to explain them as overflow phenomena, _i. e._, as expressions of the high vitality of the males, especially at this time. If he is right, then elaborate exhibitions of these kinds have evolved that have no special connection with mating. Are we called upon for a different explanation for other differences that distinguish the sexes? One example will suffice to bring out a curious emotional (?) display that, elaborate as it is, has no apparent connection with mating (p. 269): “The lapwing display, called by the natives its ‘dance’ or ‘serious dance’--by which they mean square dance--requires three birds for its performance, and is, so far as I know, unique in this respect. The birds are so fond of it that they indulge in it all the year round, and at frequent intervals during the day, also on moonlight nights. If a person watches any two birds for some time--for they live in pairs--he will see another lapwing, one of a neighboring couple, rise up and fly to them, leaving his own mate to guard their chosen ground; and instead of resenting this visit as an unwarranted intrusion on their domain, as they would certainly resent the approach of almost any other bird, they welcome it with notes and signs of pleasure. Advancing to the visitor, they place themselves behind it; then all three, keeping step, begin a rapid march, uttering resonant drumming notes in time with their movements; the notes of the pair behind being emitted in a stream, like a drumroll, while the leader utters loud single notes at regular intervals. The march ceases; the leader elevates his wings and stands erect and motionless, still uttering loud notes; while the other two, with puffed-out plumage and standing exactly abreast, stoop forward and downward until the tips of their beaks touch the ground, and sinking their rythmical voices to a murmur remain for some time in this posture. The performance is then over and the visitor goes back to his own ground and mate, to receive a visitor himself later on.”[8]