AMPHIBIANS. 3-15 



common little newt (Triton punctatus) is "brownish-gray above 

 "passing into yellow beneath, which in the spring becomes a rich 

 "bright orange, marked everywhere with round dark spots." The 

 edge of the crest also is then tipped with bright red or violet. 

 The female is usually of a yellowish-brown color with scattered 

 brown dots, and the lower surface is often quite plain." The 

 young are obscurely tinted. The ova are fertilized during the act 

 of deposition, and are not subsequently tended by either parent. 

 V/e may therefore conclude that the males have acquired their 

 strongly-marked colors and ornamental appendages through sex- 

 ual selection; these being transmitted either to the male offspring 

 alone, or to both sexes. 



Anura or Batrachia. — With many frogs and toads the colors evi- 

 dently serve as a protection, such as the bright green tints of tree- 

 frogs and the obscure mottled shades of many terrestrial species. 

 The most-conspicuously colored toad which I ever saw, the Phry- 

 niscus nigricans,** had the whole upper surface of the body as 

 black as ink, with the soles of the feet and parts of the abdomen 

 spotted with the brightest vermilion. It crawled about the bare, 

 sandy or open grassy plains of La Plata under a scorching sun, 

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

 These colors are probably beneficial by making this animal known 

 to all birds of prey as a nauseous mouthful. 



In Nicaragua there is a little frog "dressed in a bright livery of 

 "red and blue" which does not conceal itself like most other 

 species, but hops about during the daytime, and Mr. Belt says" 

 that as soon as he saw its happy sense of security, he felt sure 

 that it was uneatable. After several trials he succeeded in tempt- 

 ing a young duck to snatch up a young one, but it was instantly 

 rejected; and the duck "went about jerking its head, as if trying 

 "to throw off some unpleasant taste." 



With respect to sexual differences of color. Dr. Giinther does 

 not know of any striking instance either with frogs or toads; yet 

 he can often distinguish the male from the female, by the tints ot 

 the former being a little more intense. Nor does he know of any 

 striking difference in external structure between the sexes, ex- 

 cepting the prominences which become developed during the 

 breeding-season on the front-legs of the male, by which he is en- 

 abled to hold the female." It is surprising that these animals 



" Bell, 'History of British Reptiles,' 2nd edit. 1849, pp. 146, 151. 



« 'Zoology of the Voyage of the "Beagle," ' 1843. Bell, ibid. p. 49. 



*8 "The Naturalist in Nicaragua,' 1874, p. 321. 



*' The male alone of the Bufo sikimmensis (Dr. Anderson, 'Proc. 

 Zoolog. Soc' 1871, p. 204) has two plate-like callosities on the thorax 

 and certain rugosities on the Angers, which perhaps subserve the same 

 end as the above-mentioned prominences. 



