402 ON THE STRUCTURE AND HABITS 



proofs of His wisdom in the least attractive objects. It is thus that we find 

 more evidence of the existence of a God in the structure of an animalcule than 

 in the pompous movements of the physical universe. 



In this group, then, I have included the Wheel-animalcule (Rotifera), in 

 order to show how complicated a structure may exist in an almost invisible par- 

 ticle of organic matter. Hydatina senta, common in ponds of fresh-water, 

 possesses a strong masticatory apparatus, supplied with powerful muscles, a long 

 alimentary canal, and a highly developed nervous system. 



Perhaps nothing is more astonishing than the varieties of forms presented by 

 these little animals ; there is a little Eel-like animal called a Vibrio, which, being 

 introduced into the sap of the stems of Wheat, at last gets into the fruit, and 

 there produces such destruction as renders the grain useless. Hundreds of them 

 are contained in a single grain of Wheat, and they constitute the disease known 

 to farmers by the names of " ear-cockle" or " purples." 



Dalyell, the translator of Spallanzani, who devoted many years of his life 

 to the investigation of these animals, sums up their forms and other characters in 

 the following words : — " One is a long slender line ; another an Eel or Serpent ; 

 some are circular, elliptical, or triangular ; one is a thin flat plate ; another like 

 a number of reticulated seeds ; several have a long tail almost invisible ; or their 

 posterior part is terminated by two robust horns ; one is like a funnel ; another 

 like a bell, or cannot be referred to any object familiar to our senses. Certain 

 animalcules can change their figure at pleasure, sometimes they are extended to 

 immoderate length, then almost contracted to nothing ; sometimes they are curved 

 like a Leech, or coiled like a Snake ; sometimes they are inflated, at others 

 flaccid ; some are opaque, while others are scarcely visible from their extreme 

 transparence. No less singular is the variety of their motions ; several swim 

 with the velocity of an arrow, so that the eye can scarcely follow them ; others 

 appear to drag their body along with difficulty, and move like the Leech ; and 

 others seem to exist in perpetual rest ; one will revolve on its centre or the 

 anterior part of its head ; others move by undulations, leaps, oscillations, or 

 successive gyrations ; in short, there is no kind of animal motion, or other mode 

 of progression, that is not practised by animalcules." 



Infusoria have been lately recognised in a fossil state by Ehrenberg, a sum- 

 mary of whose observations appeared in The Analyst for October, 1837. 



The next group" of animals is very different from the last in size, structure, 

 and functions. They are called Polypiferous animals, on account of their being 

 supplied with an abundance of peculiar organs called polypi. These organs are 

 not only used for the purpose of prehension, but also by their constant movement 

 they serve to agitate the water in which these animals live, and thus bring their 

 food near them. This is quite a necessary arrangement for this class of animals,' 



