144 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 (food vacuoles')'? 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 disappear- 

 ing 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 (enclosure) and 

 an outer layer (ectosarc). What are the characteristics of each as re- 

 gards motion, clearness, firmness, etc.? Note the changes in these por- 

 tions 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 recog- 

 nizable 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 "Suggestions to Teachers"). 



186. 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. 



187. In this first and lowest group of animals, the individ- 

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



