SPIROSTOMUM. VORTICELLA. 11 



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. 



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 (moniliform) 

 macronucleus. In another species of Spirostomum the macro- 

 nucleus is similar to that of Paramecium. It is desirable to 

 examine stained specimens of the two species of Spirostomum. 



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

 occur spiral lines appear on the surface. Can you distinguish 

 these lines when the animal is extended? These 'are primitive 

 structures (myonemes) functioning as muscles. 



Make a drawing of the extended animal and a diagram show- 

 ing the form when contracted. 



VORTICELLA. 



Place a number of individuals on a slide and cover loosely 

 to avoid crushing. As usual, study first with the low power and 

 then with the high. 



1. Notice that the body of Vorticella has the general shape 



