78 OTHER NON-COLONIAL PROTOZOA 



of comparison with the protozoans already studied in detail. Draw- 

 ings should be made to illustrate the important structural features. 

 Further examination of chart and textbook figures gives one a better 

 idea of the number and variety of the types of these unicellular 

 organisms. 



Exercise 2. — Parasitic Species. 



(b) Protozoa belonging to the Class Sporozoa live as parasites in 

 the bodies of other animals. Notable among these is Gregarina, which 

 occurs in the digestive tracts of arthropods. Material for this study 

 may be obtained from the larvae or adults of the meal beetle, Tenebrio. 

 Take a living larva of the beetle on a glass slide and snip off, with 

 scissors, the last segment of the body. With forceps, tear off the head, 

 endeavoring to pull out the entire digestive tract attached to the head. 

 Cut off the head and remove from the slide. The digestive tract can 

 then be extended upon the slide, and the remnants of the cream- 

 colored fat-body that may be adhering to the tract can be removed. 

 Without adding a cover glass, examine the tract with the low-power 

 objective. The gregarines, if present in numbers, will be seen within 

 the tract as dark-colored bodies, two or three times longer than they 

 are wide. Look for a digestive tract containing a considerable num- 

 ber of the gregarines. AVhen found, such a tract may be cut into small 

 pieces and these teased apart in a very small drop of 0.99& salt (so- 

 dium chloride) solution before the cover glass is added. Very little 

 salt solution should be used, because the gregarines live longest when 

 in the normal fluid of the gut cavity. A single well-infected tract may 

 be used for the making of several preparations. As the infection with 

 any parasite is largely a matter of chance, it may be necessary to 

 examine a number of beetles or larvae before satisfactory material is 

 obtained. 



(c) Study the preparation under the high-power objective. The 

 gregarine has sharp outlines because of its firm cell membrane. The 

 cell is divided into anterior and posterior parts. Where is the nucleus? 

 Are there ectoplasm and endoplasm? Do the organisms move? How? 

 Do you find more than one type of individual? Individuals are often 

 found attached end to end. This is neither cell division, nor conjuga- 

 tion, but merely an association of the animals as they move through 

 the thick fluid in which they live. Draw a figure or 'figures, 10 cm. 

 long, to show the features observed. Compare the structure of 

 Gregarina with that of Paramecium. How is the structure and ac- 

 tivity of each related to its environment? 



(d) Encysted stages of Gregarina are not readily obtained, but 



