14 PROTOZOA. 



5. Focus carefully on the margin of the body and note a very 

 thin outer cuticle. A thick layer, the ectoplasm, devoid of gran- 

 ules but containing radially arranged, minute, oval bodies, the 

 trichocysts, is just internal to the cuticle. The inner mass of 

 protoplasm, containing the contractile and gastric vacuoles, 

 and small granules, is the endoplasm. 



6. If possible distinguish the clear, centrally located nucleus 

 (macronucleus). 



Make a sketch showing all of the above points. 



7. Kill the animal by running a drop of methyl-green under the 

 cover-glass. What happens to the cilia? To the trichocysts? 



Sketch the trichocysts with the threads protruded, and also note 

 and sketch the macronucleus and the micronucleus. 



8. Observe, if possible, animals dividing and conjugating. 



9. Study demonstrations of permanently stained specimens 

 for finer structure. 



Calkins and Cull: Conjugation of P. caudatum. Arch. f. Protistenk., 



10, 1907. 

 Jennings: Effect of Conjugation in Paramecium. Jour. Exp. ZooL, 14, 1913. 

 Metalinkow: Contributions a I'etude de la digestion. Arch d. Zool. Exp. 



et Gen., 9, 1912. 

 Woodruff: Paramecium aurelia and Paramecium caudatum. Jour. 



Morph., 22, 1911. 

 Woodruff and Erdmann: A Normal, Periodic Reorganization Process 



(Endomixis) Without Cell Fusion in Paramecium. Jour. Exp. Zool., 17, 



1914. 



Woodruff: The Structure, Life History, and Intrageneric Relationships of 

 Paramecium Calkinsi, sp. nov. Biol. Bull., vol. 41, 1921. 



SPIROSTOMUM. 



1. Compare Spirostomum with Paramecium, noting the 

 method of locomotion, the shape of the body, the ciliation, the 

 buccal groove and mouth, and the large excretory reservoir, fill- 

 ing the posterior end of the body and in communication with 

 the anterior end of the body by a canal. 



2. Note the highly refractive, long, band-like (^noniliform) 

 macronucleus. In another species of Spirostomum the macro- 

 nucleus is similar to that of Paramecium. 



3. Note the sudden contractions of the body. When these 



