1 68 THE INFANCY OF ANIMALS \ 



survive unless their wearers live in situations where such 

 a type of coloration tends to render them in harmony 

 with their surroundings ; nor can the creatures keep their 

 pale spots amid desert surroundings. For it is a well- 

 ascertained fact that when spots occur in desert-dwelling 

 animals, they are dark on a light ground, as is exemplified 

 among reptiles by some of the sand skinks (Chalcides) and 

 among mammals by leopards and servals ; while among 

 forest-dwellers, light spots on a dark ground are the fashion, 

 as in the fallow-deer and the Indian spotted deer. 



In the young of the " painted terrapin " (Chrysemmys 

 picta), there is a conspicuous stripe of bright orange running 

 down the middle of the carapace, or back shield, while the 

 naked neck, limbs and tail bear numerous narrow longi- 

 tudinal lines of yellow on a blackish-brown ground colour. 

 Gradually a line of orange or red appears down the middle 

 of each of these yellow bands, and the yellow band down 

 the back disappears, to be replaced by transverse bars of 

 yellow. ^ 



In the soft-shelled fresh-water turtles of the genus 



Irionyx the young are profusely spotted, indicating an 



earher striped condition. But in the Indian Trionyx 



hurum and the Burmese Trionyx fermosa these spots are 



augmented by two pairs of large black and yellow, eye-like 



spots on the back of the shield, whose purpose is difficult 



to imagine. Difficult because, according to current 



theories, such spots are generally borne on areas which 



may be damaged with impunity, and serve as lures to 



draw off the attention of predatory animals from the vital 



parts of the body. In butterflies, for example, the spots 



commonly occur on the edge of the wing, so that birds, in 



chasing them, snap at the fragile wing membrane and 



Jeave the vital organs uninjured. But the " eyes " in thes? , 



