What is Infusoria, the Little Animals?

by Henry Hottenstein

Infusoria are minute animals abounding in waters that contain decaying animal and vegetable matter.

They are protozoa which are ciliated either through life or in the young condition.  Some authorities therefore call them ciliata. 

The form of its body varies.  Like other protozoa it consists of a single cell, which may be roundish, kidney shaped, ovoid, vase-shaped, trumpet shaped or flattened. 

Some are free-swimming, others are attached to stones, weeds or sticks by a stalk.  Still others are parasitic.  In some species the stalk is quite firm, in others it is very contractile, and can coil like a corkscrew when the animal is stimulated in any way. 

Like the amoeba, the body of Infusoria consists of soft, transparent protoplasm, but unlike the amoeba, this protoplasm is surrounded by a thin but firm wall, so that the shape of the body can not be so readily altered. 

From the outer layer of the protoplasm, fine, thread-like projections extend through the wall into the water in which the animal lives.  These thread-like projections are called cilia (the singular of this word is cilium).  The cilia aid in locomotion and also in getting food. 

The arrangement of the cilia is not the same in all infusoria.  In some species the cilia are small, nearly equal in size, and distributed in rows all over the body of the animal. 

In others the cilia are of unequal size, the larger being found usually near the place where food is taken in. 

In others a row of large cilia is found near the mouth-end, with the rest of the body being quite naked. 

The highest form of infusoria may have cilia that take the shape of hooks, fans, bristles, and plates with fringed ends.  They are much stronger than those of ordinary infusoria, and are therefore used by the animal much like an insect uses its legs.  

The amoeba ingests food by surrounding it, but that's not how insuforia eat.  In forms, not the parasitic type, there are definitely a mouth or a depression through which food enters.  The food in question would be algae or other small organic particles found in water. 

Their way of reproduction is quite interesting - it takes place almost exclusively by means of a simple division or fission, one animal dividing into two equal or nearly equal parts. 

Infusoria received their name from the fact that they are usually found in infusions, that is in water in which hay, grass or other organic material is soaking. 

If you'd like your own infusoria farm for personal study under a microscope in your room perhaps, all you need do is place a handful of hay in a jar and pour cold water over it.

Heck knows where they actually come from, but in a few days the water should be teeming with microscopic ciliated animals. 

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