50 



THE SIMPLEST ANIMALS — PROTOZOA 



31. Paramecium. — One of the most common forms of 

 Protozoa is the slipper-shaped paramcecium (para-me'- 

 shi-um), which is more active than the amoeba. It is 

 abundant in stagnant water and in the hay infusions pre- 

 pared in the laboratory. (See Laboratory Suggestions.) 



LABORATORY STUDY 



There are certain kinds of Protozoa that are usually found in protozoan 

 cultures. The most abundant form is the paramoecium. Make repeated 

 examinations of drops of water from the protozoan culture, until you are 

 able to find the paramoecium. Notice its shape, rate of movement, be- 

 havior on meeting obstacles, and the like. Report on what you can 

 make out. Compare the paramcecium with any other protozoan you can 

 find, as to shape, rate of movement, size, color, etc. If available, ex- 

 amine slides which show the nucleus of a protozoan. Make sketches 

 that illustrate the above features. 



32. Structure of Paramcecium. — The paramoecium, like 

 the amoeba, is a single cell, but it has both a large nucleus 



and a small one. It has 



0$& 



Contractile.. 

 Vacuole 



-L 



•Cilia 



•Cuticle 



Trichocysts 



an endoplasm, an ecto- 

 plasm, and a cuticle 

 (ku'ti-kl), or cell wall. 

 Through the cuticle, 

 there extend great num- 

 bers of cilia (sil'i-a), or 

 threads of living proto- 

 plasm. The ectoplasm 

 contains many thread- 

 like darts known as 

 trichocysts (trlk'o-sists). 

 These can be discharged. 

 On one side is a fold or 

 depression (the gullet) 

 in which food is collected by the waving motion of the 

 cilia. Within the cell are found food and water vacuoles 



Food 

 Vacuole 



•Contractile 

 Vacuole 



Figure 48. — Diagram of Paramcecium. 



