14 THE UNIVERSE. 



ture has expended the most watchful care upon them. 

 Some of them are sheltered beneath a calcareous coat of 

 mail ; and in many the protecting shell is indestructible, 

 and of the nature of flint, being formed of silex. 



According to Ehrenberg, some of the Infusoria have 

 even eyes, which at times present the appearance of flame- 

 red pupils. If we could suppose organs of such minute- 

 ness possessing a field of vision large enough to allow these 

 animalcules to see us with the instruments which we use to 

 observe them, can we imagine what a terrific impression 

 we must make upon them when they see themselves in our 

 hands ? 



Lastly, many of these animalcules have, in the interior 

 of the body, large cavities, which incessantly empty and fill 

 themselves with colored fluid. These cavities represent the 

 heart of large animals, and their fluid the blood ; and this 

 circulating system is relatively so large that it may be 

 stated, without any exaggeration, that some microscopic 

 beings have hearts fifty times as large and as strong in pro- 

 portion as that of the horse or ox. 



If the wonderful organic perfection of those living cor- 

 puscles surpass all our preconceived ideas, their perpetual 

 activity affords ground for no less astonishment. The life 

 of all animals is made up of alternate action and repose, of 

 movement which wastes the forces, and sleep which repairs 

 them ; but the Infusoria are strangers to anything of the 

 kind ; their life is an emblem of incessant agitation. Eh- 

 renberg, who observed them at all hours of the night, al- 

 ways found them in movement, and accordingly concluded 

 that they had neither rest nor sleep ! Even the plant, ex- 



