26 SEXUAL SELECTION. Part IL 



could not fail to catch the eye of every passing creature. 

 These colours may be beneficial by making this toad 

 known to all birds of prey as a nauseous mouthful ; 

 for it is familiar to every one that these animals 

 emit a poisonous secretion, which causes the mouth 

 of a dog to froth, as if attacked by hydrophobia. 1 

 w^as the more struck with the conspicuous colours of 

 this toad, as close by I found a lizard (Proctotretus 

 muUimaculatus) which, when frightened, flattened its 

 body, closed its eyes, and then from its mottled tints 

 could hardly be distinguishable from the surrounding 

 sand. 



With respect to sexual differences of colour. Dr. Giin- 

 ther knows of no striking instance with frogs or toads ; 

 yet he can often distinguish the male from the female, 

 by the tints of the former being a little more intense. 

 Nor does Dr. Giinther know of any striking difference 

 in external structure between the sexes, excepting the 

 prominences which become developed during the breed- 

 ing-season on the front-legs of the male, by which he 

 is enabled to hold the female. The Megaloplirijs mon- 

 tana"^^ (fig. 32) offers the best case of a certain amount of 

 structural difference between the sexes ; for in the male 

 the tip of the nose and the eyelids are produced into 

 triangular flaps of skin, and there is a little black 

 tubercle on the back — characters which are absent, or 

 only feebly developed, in the females. It is surprising 

 that frogs and toads should not have acquired more 

 strongly-marked sexual differences ; for though cold- 

 blooded, their passions are strong. Dr. Giinther informs 

 me that lie has several times found an unfortunate 

 female toad dead and smothered from having been 

 so closely embraced by three or four males. 



41 ' The Eeptilfcs of India,' by Dr. A. Giinther, Eay Soc. 1864, p. 413. 



