152 ZOOLOGY 



II. With the high power, study, — 



3. Cilia: where found? Are they uniform in length? How do they act? 

 What results do they produce? (Place a small amount of water containing finely 

 powdered indigo or carmine at edge of cover-glass. If the movements are too 

 rapid a little gelatine added to the water will be of advantage.) 



4. Find the mouth, with the oral groove leading to it. Position and shape? 

 How are food particles captured? Can you find them within the body (Jood 

 vacuoles) ? How are the food vacuoles formed ? Do the food vacuoles move within 

 the cell? If so, trace their course? What finally becomes of them? Evidences? 



5. Contractile vacuoles (clear spherical objects rhythmically disappearing and 

 reappearing). Number? Position? Rate of contraction? Do they contract 

 at the same time? What becomes of the clear material during the contraction of 

 the vacuole? Are they deep or superficial structures? Your evidences? Does 

 change of temperature cause any change in their rate of contraction? 



6. Distinguish between the inner mass of protoplasm (endosarc) and an outer 

 layer {ectosarc). What are the characteristics of each as regards motion, clearness, 

 firmness, etc. ? Note the changes in these portions on the addition of dilute acetic 

 acid or iodine at the edge of the cover-glass. 



7. Discover, if possible, nuclear bodies. These are not usually recognizable 

 without careful staining. Place at the edge of the cover-glass, in a fresh preparation 

 of Paramecia, a drop of 5-10% aqueous solution of methyl green. Compare the 

 result with a permanent mount stained by suitable methods (see Appendix: Sug- 

 gestions for the Laboratory). 



191. Other Protozoa. — The pupils should examine stagnant water for as many 

 types of protozoa as may be found. Compare these, noting the points of similarity 

 and difference in general structure and activities. Especially profitable protozoa 

 for laboratory work are the green flagellate infusorian, Euglena, which often tinges 

 the water, or forms a green scum over shallow pools of water; the colonial ciliate 

 form, Vorticella, found attached to submerged objects in ponds or pools of slowly 

 moving streams in which there is considerable decaying organic matter. The 

 colonies are easily visible to the naked eye. Stentor is a very large trumpet-shaped 

 infusorian which may be alternately attached and free-swimming. It lives upon 

 submerged sticks and leaves and may often be found attached to the sides of 

 vessels in which such matter has been placed. In all such studies and identifica- 

 tion of the protozoa the student should seek evidence of the unicellular character 

 of the organism. 



Descriptive Text 



192. In this first and lowest group of animals, the individu- 

 als of which consist of single cells or loosely associated simi- 

 lar cells, we find something of the variety of shape which we 

 observed in the tissue cells of the higher animals (Chapter V). 

 The Protozoa are especially interesting to the biologist because 

 they represent the simplest forms of animal life now found 

 on the earth and because some of their representatives are very 



