Forest Preserve District of Cook County, Illinois
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Moss Animals
Nature Bulletin No. 138   January 17, 1948
Forest Preserve District of Cook County
William N. Erickson, President
Roberts Mann, Supt. of Conservation

Last summer, several visitors in the forest preserves were puzzled by finding masses of jelly-like substance stuck to sunken sticks in certain ponds and lakes.

These masses were usually round or egg-shaped, ranging in size from that of a tennis ball to that of a football. On the outside they were covered by a grayish scum with faint lines in a coarse design. Inside there was apparently nothing but a clear colorless jelly that quivered and shook like a well-chilled gelatin dessert. One man guessed that it was some sort of garbage; another, reasonably, that it was some strange plant growth.

As a matter of fact, each mass was a colony of thousands of tiny animals. These animals do not have true heads but each has a mouth, surrounded by a ring of microscopic tentacles, on the end of a long slender neck. On each tentacle are hundreds of still smaller hair-like projections which sweep minute water plants and animals through the mouth into the U-shaped alimentary canal. At the slightest jar they snap their mouths and necks back into shallow tunnels in the jelly mass. This protects them against nibbling enemies such as small fish, water neas and swimming insects.

They are Bryozoa, which means " Moss Animals" in English. In the freshwaters of this region there are several other kinds of moss animals which form colonies in thick crusts, or as feathery branching tubes, stuck to boats, sticks, stones, fishermen' s nets, and the underside of lily pads..

Moss animals, like sponges and the jellyfish tribe, are primitive animals that have a multitude of relatives in the sea. In the Niagara limestone rock underlying the Chicago region, we find skeletons of many ancestors of these moss animals that lived in the sea that once covered this part of the continent and deposited the materials which made that rock.

Like some people, they stick their necks out when they open their mouths.

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