MICROSCOPIC ANIMALCULES. 49 



ed upon the contractile fibres, and therefore are 

 motions which never tire. We may thus ex- 

 plain the fact which Ehrenberg relates not 

 without an expression of surprise namely, that 

 at whatever period of the night he examined 

 the living Infusoria, he invariably found them 

 moving as actively as in the day-time ; in short, 

 it seems to him that these little beings never 

 sleep." 1 



This life of ceaseless activity is indeed not 

 long : but the watchful devotee of science has 

 traced an infusoria through a course of exist- 

 ence, extending to an old age of twenty-three 

 days ! 



4. To a true Animalcule, of high and com- 

 plex organization, brought to view by the 

 Microscope, we must still request our reader's 

 attention ; namely, the Rotifer, or " Wheel 

 Animalcule" These animalcules belong to the 

 articulated division of the animal kingdom, 

 and seem to constitute a class in that lower 

 portion of it, to which the designation worm 



1 Lectures on the Compar. Anatomy and Physiology of the 

 Invertebrate Animals, p. 19. 1843. 

 D 



