paramecium,on theotherhand,never changes shape. Itlooks verymuchlike
the soleofa shoe, and itdartsswiftlyaroundthe water.
A particularly interesting type of protozoa has a tiny, chalk-like cell
aroundits one-celled body. The famouschalkcliffs ofDover,on thesouthern
coastofEngland,are made up of countless numbersof chalk-like cellsthat
were washed up by the seaafterthesoft-bodiedanimalsthemselves died.
Some protozoaare disease-producing animals. We call themparasites.
Malariais oneofseveral diseases caused by aparasiticprotozoa.
MAKING ACOLLECTION OF SEA SHELLS AND ANIMALS
Materials: The next time you go to the seashoremake a collectionof
interestinglyshapedand tintedsea shells and of some of the small seaanimals
you may find washed up on the sand. When you are home againandwantto
preserveyourcollectionofthese objects, you will need stickycellophanepaper,
a large roll ofabsorbentcottonand acardboardbox bigenoughto holdyour
shells and sea animals.clam~1I0'
Follow this procedure:Starfish should be weighted down in a flatposition
and allowed to dry in the sun. Sand dollars willnothave to be weighted, for
they are flat, but they, too, should be dried in the sun asshouldcrabsand
young crayfish. If you prefer, you can preserve crabs in a tightly coveredjar
containingalcohol. The shells of oysters, clams, mussels and snailsshouldbe
boiled in water in an enamel pot for ashorttime, and then completely dried.
Label each specimen (you can attacha pieceofpaperto it with sticky
cellophanetape), cover it withtransparentkitchenwrappingpaperand place
it in a largecardboardboxabouthalf-filled withabsorbentcotton.Starfish, sand dollars, crabs, oysters, clams, mussels, snails and crayfish
inhabitthe relatively shallow areas of bodies of salt water. Since their bodies