CHAPTER VI 

 ONE-CELLED ANIMALS (BRANCH PROTOZOA) 



The Amoeba which has just been studied is one of the sim- 

 plest of the one-celled animals. Others while still retaining 

 the one-celled condition, become more highly specialized along 

 certain lines and show a wonderful power to adapt themselves 

 both in form and habits to the various conditions under which 

 they live. A brief study of a few of these will be worth while. 



Paramoecium. Paramcecia are usually found in considerable 

 numbers in any pond of stagnant water. A good supply can 

 often be obtained by placing sticks or leaves from a pond, 

 together with some dry hay or clover, in a dish, which is then 

 filled with water and allowed to stand for several days. When 

 very abundant the Paramoecia may even be seen with the 

 unaided eye as minute white specks near the edge of the dish. 

 Examined with the low power of the microscope they will be 

 seen as very active, slipper-shaped animals much larger than 

 the Amoebae. As they move about so rapidly it is desirable 

 to put them into some thicker medium, such as a thin mixture 

 of cherry gum; or a few shreds of cotton may be put under 

 the cover-glass and some of the Paramcecia will become en- 

 tangled in this in such a way that they may be studied. 



It will at once be seen that Paramoecium differs from Amoeba 

 in many respects. It has a definite and persistent elongate- 

 oval shape, roughly like that of a slipper, hence it is often 

 called the slipper animalcule. There are definite anterior 

 and posterior ends and dorsal and ventral sides, and the body is 

 covered with minute cilia, fine hair-like projections, which 

 vibrate very rapidly and propel the animal through the water. 

 On one side, beginning at the anterior end and extending more 

 than half the length of the animal, is a buccal groove, which is 

 provided with many small cilia which drive water currents and 



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