40*2 
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 44 ear-cockle” or 44 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 :— 44 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, 
