In this species, in short the male plays successively a polygamous and a polyandrous rôle. Strange as these facts are, they are not apparently without parallel among fishes, for certain of the labyrinth-gilled fish present many features in common, though as yet proof seems to be wanting. Thus the small Siamese “Fighting Fish” (_Betta pugnax_) is endowed with so ferocious a nature that it is kept, as the Malays keep fighting cocks, for the amusement of native sportsmen, two fish being pitted against one another and large bets being made on the result. In a state of quiescence it presents no very remarkable coloration, but if two be brought together, or if one sees its image in a looking-glass, it becomes thrown into a paroxysm of rage, the fins are raised and the whole body becomes irradiated with metallic colours of dazzling beauty. There can be no doubt but that a like play of colour occurs during moments of sexual excitement; it is highly probable that it is polygamous. Of its breeding habits, however, little or nothing seems to be known. Not so, however, in the case of a closely-related species, less pugnacious in disposition, but almost as vividly coloured, in so far as the male is concerned. Now in this species a nest of froth is made and the eggs, after deposition therein, are jealously guarded by the male. Hence, on these facts, we may assume with a fair amount of certainty that the closely-related “Fighting Fish” displays like habits. That the Reptiles, Amphibia and Fishes have much in common with one another, and with the higher vertebrates, in the manner of their love-making is indisputable. We find no evidence anywhere that the first faint throbbings of the sexual pulse in the female are quickened to fever beats after the efforts of several successive wooers, each more demonstrative than the last, to arouse this state—the conditions required by the Sexual Selection theory. But successful mating depends, in each year, on the sexual fitness of the male himself, and the mate, or mates, which for that year he has taken “for better or worse.” It is possible, of course, that a male, ambitious but impotent, will be forsaken by his mate; it is possible that a female of low sexual vitality may fail to respond to the most impassioned displays; in either case no offspring result, and thus the failures are eliminated. It is possible that here, as with the higher vertebrates, coition may by no means always be immediately preceded by display. But the “display” has done its work. It has stimulated the sexual appetite, as the sight of tempting food stimulated the bodily appetite.