65 



from a dark red, to a pale pink, by secluding them 

 from light. The parts of fish, which are exposed to 

 light, exhibit various colours ; but the belly, which 

 is deprived of light, is uniformly found white in all 

 of them. The birds that inhabit the tropical coun- 

 tries, are much brighter coloured than those of the 

 north : and those parts of the feathers, which are 

 exposed to light, are almost always coloured, while 

 the parts secluded from light are generally pale or 

 white. The same observations apply to the hairs of 

 quadrupeds : and, not only are the beasts of the 

 equatorial uniformly brighter coloured than those of 

 the polar countries, but the northern animals are 

 dark coloured in summer, and white, or pale, in 

 winter *. These observations point out the influence 

 of light, in giving rise to the colour of animals ; but 

 they do not, any more than in vegetables, shew the 

 immediate necessity of it to the existence of animal 

 action. 



5\. But when, by the combined agency of water 

 and heat, the animal structure is brought into a con- 

 dition fitted for exhibiting living action, the presence 

 of atmospheric air is required to enable it to con- 

 tinue this action ; for, as far as observation has ex- 

 tended, no living being can long subsist without a 

 due supply of fresh air, " In insects," says Mr Ray, 

 " there are many orifices on each side of their 

 bodies for the admission of air, which, if you stop 

 with oil or honey, the insect presently dies, and re- 

 yives no more. This, he adds, was an observation 



* Contribution* to Science by Beddoes, p. 192- 



