PROTOZOA 151 



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 (food 

 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 5-10% aqueous solution of methyl green. Compare the result 

 with a permanent mount stained by suitable methods (see Appendix : Suggestions 

 for the Laboratory). 



191. Other Protozoa. If the class is supplied with microscopes, the pupils 

 should be allowed to examine stagnant water for as many types of protozoa as 

 may be found. Allow them to 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 identification of the protozoa 

 the question of evidence of the unicellular character of the organism should be kept 

 before the student. 



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 



