OBSERVING PROTOZOA
Materials: Your hay infusion, a medicine dropper, a small piece of
absorbentcotton. This is amicroscopestudy, so you will need a clean slide
and a cover slip, too.
Follow this procedure:Placea fewstrandsofabsorbentcottonin the middle
ofa clean slide. Thecottonstrandswill tend to keep the more activeprotozoa
confined sothatyou can observe them. Very carefully, so as not to stir up
the infusion, take somewaterfrom thebottomof thejarwithyourmedicine
dropper.
Place adropof this water on thecottonlying onyourslide. Cover care-
fully with aroundcover slip. Observe firstunderlow power, and thenunder
high power ofyourmicroscope.
Now, preparea second slidejustas you did the first. There is one differ-
ence,though; this time take yourspecimen from thesurfaceof theinfusion.
Comparewhatyou see on the two slides.
You will observe:Afteryour eye becomesaccustomedto the lightnessof
the water, you will see tiny formsofmovinganimallife. Someprotozoawill
bedartingback andforthacrossyourfield of vision. Some will seem to be
tumblingover and over, like the rolling barrels in a "funhouse." Others
will glide lazily along, while stillotherswill seem to ooze sluggishly. You will
seeprotozoaofmanydifferent shapes and sizes.
These tiny bitsofindependentlife(protozoa)are animals whose bodies
consistof only one cell. Varietiesofthese one-celledanimalsmay befound
in pools, ponds,lakes, rivers, even in oceans and seas. Althoughmanylive
by themselvesindependently,some lovecompanyand exist ingroups. There
are types ofprotozoawho feel at home at thebottomofa body ofwaterand
othertypes who prefer the betterlightedpartofthe water nearthe surface.
However, allprotozoaserve as food for larger, water-living animals.
The two best-knowntypesofprotozoaare the amoebaand the para-
mecium. Theformerresembles anirregularlyshapedblobofprotoplasm. It
changes its shapeconstantlyas it oozes slowly from oneareatoanother. The