WHEEL ANIMALCULES. 191 



circumference ; each part, in succession, be- 

 coming alternately convex and concave, and 

 thus producing the appearance of the actual 

 advance of the portions that are raised ; while 

 their real motions are only those of elevation and 

 depression, by the elongation and contraction of 

 their perpendicular fibres. 



Besides possessing extensive powers of loco- 

 motion, the infusoria manifest in several of 

 the vital functions, as we shall hereafter find, a 

 degree of complication, which appears to entitle 

 them to a higher station in the animal scale, 

 than that which most naturalists have assigned 

 to them. They are certainly superior to the 

 sponges or the polypi, doomed by nature to be 

 permanently fixed, like plants, to the same spot; 

 and of which, if we consider them as compound 

 beings, the individual animals are often so mi- 

 nute as to be scarcely visible without the aid of 

 the microscope. Mere size, indeed, is of all the 

 circumstances attendant on organized beings, 

 that which should least be assumed as the crite- 

 rion of complication or refinement of structure. 

 An object is great or small, only in relation to 

 the standard of our own limited and imperfect 

 senses ; but with reference to the operations of 

 creative power, all such distinctions must vanish. 

 There is not, as far as we have the means of 

 judging, in the colossal fabric of the elephant, any 

 structure more complicated than exists in the 

 minutest insect that crawls unheeded at our feet. 



