REPTILES AND AMPHIBIANS 1 47 



Most of the amphibians that secrete offensive matter 

 are brightly coloured. The fire-salamander catches the 

 eye at once with its bright yellow spot on a black 

 ground, the newt or water- salamander has a yellow 

 belly, like the ringed snake ; the latter have been seen 

 to throw themselves on their backs at the approach of 

 danger, so that the yellow under-side is suddenly 

 presented to the astonished pursuer. 



Light colouring is very common amongst malodorous 

 and poisonous animals and plants. Of plants we have, 

 for instance, the fox-glove, the laburnum, and many 

 poisonous fungi ; but as the flowers of most plants 

 are brightly coloured — for reasons that we shall see 

 in the sixth chapter — the poisonous flowers are not 

 very conspicuous. This is more the case with the 

 animals. Besides our amphibia, a number of malodor- 

 ous and nasty-tasting butterflies and many marine 

 polyps are brightly coloured. OflTensive and poisonous 

 organisms show red or, more generally, yellow colours ; 

 it can hardly be a matter of chance that in the colour- 

 language of lovers yellow is regarded as a sign of hatred 

 and aversion. 



It is easy to see why natural selection has given a 

 striking appearance to poisonous and obnoxious animals. 

 It is an advantage to them to be recognised at once as 

 inedible and dangerous. What use is it to an obnoxious 

 animal if the assailant does not know that it has a nasty 

 taste, and has to convince himself of it ? The victim 

 has generally to die under the test. So their poison is 

 of no use to poisonous organisms if their enemies do not 

 know them. The enemies die also after eating them, 



