SEX AND REPRODUCTION 6; 



expand a great throat-pouch they possess, lash their tails from 

 side to side, and then, worked up to the requisite pitch of fury, 

 rush at one another, rolling over and over, and holding firmly 

 with the teeth. The conflict generally ends by one of the com- 

 batants losing his tail, which is eaten by the victor. 



Dr. Gadow states that in the breeding season the males of 

 a Malay lizard (Calotes emma) " are very pugnacious and change 

 colour as they fight. At the time of courtship a curious per- 

 formance is gone through by the male, the females 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 up- 

 right, 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." 



That instances of this kind are by no means rare there can 

 be no doubt, but records of actual observation are few. Those 

 cited show the nature of the evidence so far collected, but on 

 the whole there is less activity and intensity of feeling displayed 

 by reptiles in their choice of mates than is the case with birds. 



Similarly, in the care displayed for their offspring reptiles 

 are far behind birds. As already mentioned, reptiles are pro- 

 perly oviparous, laying eggs from which the young are usually 

 hatched by the heat of the sun or by that engendered by decay- 

 ing vegetable matter, without any aid from either parent. In 

 many species, however, such as the common viviparous lizard 

 {Lacerta vivipard) the young burst the shells of the eggs immedi- 

 ately after they are laid, or in some cases even before they are 

 laid. Although in the latter instance the species may be said to be 

 viviparous, the term ovo- viviparous is properly applicable to this 

 mode of reproduction. At least one reptile, namely the Austra- 

 lian stump-tailed lizard ( Trachysaurus rugosus) is, however, really 

 entitled to be called viviparous, for not only are the young 

 born free, but the hard calcareous shell characteristic of the 

 eggs of reptiles in general is never developed. These differ- 

 ences in the mode of reproduction are probably in all cases 



