The display of a vividly coloured mouth during moments of sexual excitement, it may be remembered, occurs in some birds. Among reptiles it is a common feature. A good illustration of this is furnished by the Moustached Lizard (_Phrynocephalus mystaceus_), a native of Southern Russia. When violently excited it raises itself on its hind legs, curls and uncurls its tail, and opens its mouth to its widest extent, presenting, to our eyes, a quite fearsome aspect. This effect is immensely increased by the fact that the corners of the mouth are provided with flanges of skin, which at this time swell up into crescentic plates, the inner borders of which pass gradually into the rosy lining of the mouth, thereby causing it to appear much wider than it really is. So far this display has been witnessed only when the animal is under the influence of fear. But since we find that birds will make similar displays, both when under the stimulus of fear and that of sex, we may assume, with no little degree of certitude, that the same applies in the case of the reptiles, for the origin of the ornaments is almost certainly to be attributed to the same gland secretions which produce the secondary sexual characters of birds and beasts. This, however, is no mere assumption, for we have some positive evidence as to the association of bright coloration with “courtship,” which has been furnished by Mr. Annandale, a naturalist of long experience and having a first-hand acquaintance with tropical life. He has given us a lively description of the courtship of the Malayan Lizard (_Calotes emma_). “The males,” he says, “are very pugnacious, and change colour as they fight. At the time of courtship a curious performance is gone through by the male, the female remaining concealed in the foliage hard by. He chooses some convenient station, such as a banana-leaf, or the top of a fence, and advances slowly towards the female. His colour is then pale yellowish flesh colour, with a conspicuous dark spot on each of the gular pouches, which are extended to their utmost. He stands upright, raising the fore-part of the body as high as possible, and nodding his head up and down. As he does so the mouth is rapidly opened and shut, but no sound is emitted. When he is driven away, caught, or killed, the dark spot disappears entirely from the neck.” [Illustration: Plate 30. Photo by W. Saville-Kent. THE BEARDED LIZARD. Paring moments of excitement the Bearded Lizard opens the mouth widely displaying a vividly coloured interior. Face page 166]