SOME "COLD-BLOODED" LOVERS 165 



with all the colours of the rainbow. Having regard to 

 what has been said already as to the sources of this 

 coloration it is not surprising to note that here also the 

 males are the more vividly coloured whenever the sexes 

 differ in this particular. And further, it is among the 

 most vividly coloured males that most animated displays 

 take place when the endeavour is being made to excite the 

 amorous instincts of the females. 



The males of the genus Sitana are very brightly garnished. 

 They possess a large throat pouch, coloured blue, black, 

 and red when expanded, and this occurs only during 

 moments of excitement, whether this is due to fear or 

 pleasure. And at the same time the vividness of the 

 coloration is greatly increased. No such secondary sexual 

 characters are present in the female. 



A variant on the throat pouch, of a much more striking 

 character, is displayed by the Frilled Lizard {Chlamy- 

 dosaurus kingi), wherein the tongue bones have become 

 enormously elongated so as to project backwards on each 

 side of the body almost as far as the base of the tail. 

 With them they have carried a thin fold of skin, so that 

 whenever the mouth is opened these bones stand out at 

 right angles to the head and display a circular fold of skin 

 stretched as it were on rods ; or they may be compared 

 to the ribs of an umbrella. The great Elizabethan frill 

 thus formed, is displayed only during moments of great 

 excitement, and the open mouth, at such times, is flushed 

 with a vivid red, which, contrasting with the teeth, gives 

 a very terrifying aspect to prospective enemies, and 

 doubtless also proves a valuable asset as a " secondary 

 sexual character." 



The display of a vividly coloured mouth during moments 

 of sexual excitement, it may be remembered, occurs in 



