NATURAL HISTORY. 



213 



" Whose snout hath rooted up 



The fruitful vineyard of the commonwealth." 



BEAUMONT AND FLETCHEB. 



The reason of this will be readily understood by those who are aware how mach 

 more easily a boat is pulled by oars nearly on a level with the water than when th 

 oars have to dip deeply into the water, and are used near the bows. 



638. Why ham certain species of animals sharp-pointed snouts ? 



To enable them to seek their 

 nourishment from the ground. 

 Thus the tapir species, nearly 

 allied to the hog, have 

 their noses much prolonged in 

 front of the mouth, constitut- 

 ing a little trunk, capable of 

 lengthening and shortening 

 itself. The shrews and small 

 insectivorous animals, nearly 

 allied to the shrew, but 

 .formed to swim with ease, and 



to live at the bottom of burrows hollowed in the banks of rivers, 



also exhibit a similar conformation. (See 466.) 



639. Why is the fur of some animals changed in the winter from 

 a dark to a white colour? 



Because, although the darker colours absorb heat to a greater 

 degree than the lighter ones, so that dark-coloured clothing is much 

 warmer than light-coloured, where the wearer is exposed to the sun's 

 rays, the radiation of heat is also much greater from dark than from 

 light-coloured surfaces, and consequently the animal heat from 

 within is more completely retained by a white than by a dark 

 covering. The temperature of an animal, therefore, having whita 

 fur, would continue more equable than that of one clothed in 

 darker colours, although the latter would experience a greater 

 degree of warmth when exposed to the sun's rays. Another reason 

 may be that the mottled browns, which form the principal colours of 

 the animals alluded to, although well adapted for their concealment 



