12 PROTOZOA. 



4. Observe the contractile vacuoles. How many are there? 

 Is their position constant? What is their action? In com- 

 pressed specimens the contractile vacuoles and their reservoirs 

 are usually conspicuous. Note the order of appearance and 

 disappearance of the vacuoles and reservoirs. 



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 shouting 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. Protist., 10, 1907. 

 Jennings and Hargitt: Characteristics of the Diverse Races of Paramsecium. 



Jour. Morph., 21, 1910. 

 Metalinkow: Contributions & l'e"tude de la digestion. Arch d. Zool. Exp. 



et Gen., 9, 1912. 



Schaeffer: Selection of Food in Stentor cseruleus. Jour. Ex. Zool., 8, 1909. 

 Woodruff: Paramsecium aurelia and Paramsecium caudatum. Jour. 



Morph., 21, 1910. 

 : A Five Year (3000 generations) Pedigreed Race of Paramsecium 



without Conjugation. Proc. Soc. Ex. Biol. and Med., 1912 (also Biol. 



Centr., 33, 1913). 



SPIROSTOMUM. 



1. Compare Spirostomum with Paramsecium, 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. 



