Fig. 18.—Euglena.
We thus see that the paramecium, though of only one cell, is a much more complex and advanced animal than the amœba. The tiny paddles, or cilia, the mouth-groove, etc., have their special duties similar to the specialized organs of the many-celled animals to be studied later.
Fig. 19.—Shell of a Radiolarian.
If time and circumstances allow a prolonged study, several additional facts may be observed by the pupil, e.g. Does the paramecium swim with the same end always foremost, and same side uppermost? Can it move backwards? Avoid obstacles? Change shape in a narrow passage? Does refuse matter leave the body at any particular place? Trace movement of the food particles.
Draw the paramecium.
Which has more permanent parts, the amœba or paramecium? Name two anatomical similarities and three differences; four functional similarities and three differences.
The amœba belongs in the class of protozoans called Rhizopoda “root footed.”
Other classes of Protozoans are the Infusorians (in the broad sense of the term), which have many waving cilia (Fig. [17]) or one whiplike flagellum (Fig. [18]), and the Foraminifers, which possess a calcareous shell pierced with holes (Fig. [19]). Much chalky limestone has been formed of their shells. To which class does the paramecium belong?
Protozoans furnish a large amount of food to the higher animals.