26 
SEXUAL SELECTION. 
Part II. 
could not fail to catcli 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, vrhich causes the mouth 
of a dog to froth, as if attacked by hydrophobia. 1 
was the more struck with the conspicuous colours of 
this toad, as close by I found a lizard (Prodotretus 
muUimaculatus) wdiich, when frightened, flattened its 
body, closed its eyes, and then from its mottled tints 
could hardly be distinguishable from the surrounding 
sand. 
AVith respect to sexual differences of colour. Dr. Gun- 
ther knows of no striking instance wdth 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. Gunther know of any striking difference 
in external structure between the sexes, excej)ting 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 Megalophrys mon- 
iana'^^ (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 he has several times found an unfortunate 
female toad dead and smothered from having been 
so closely embraced by three or four males. 
‘ Tiie Eeptiles of India,’ by Dr. A. Giinther, Eay Soc. 1861, p. 413. 
