28 PROTOZOA 



Make a drawing of the extended animal and a diagram 

 showing the form when contracted. (See Doflein and Reich- 

 enow.) 



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 of an inverted bell. The covering of the body is a 

 very thin transparent layer, the cuticle, underneath which is 

 the peripheral layer of ectoplasm enveloping the more fluid 

 and granular endoplasm. 



2. The peristome is the rounded rim about the base of the 

 bell. 



3. The elevated and inclined area included within the 

 peristome, and ciliated around the edge, is the disk. It is 

 somewhat convex. 



4. The marked depression between the disk and the per- 

 istome is the vestibule. It is also lined with cilia. The ves- 

 tibule defines the ventral surface of the animal. 



5. The gullet, a slender canal, leads from the vestibule 

 toward the center of the body. 



6. The feces escape from the body by the side of the ves- 

 tibule. The opening is temporary. 



7. Within the endoplasm are situated the clear contractile 

 vacuole, several food vacuoles, the long U-shaped macronu- 

 cleus, and the small round micronucleus. The macronucleus 

 may be made more distinct by treating with methyl green. 



8. The stalk is composed of a sheath, which is continuous 

 with the cuticle of the body, and, within the sheath, the con- 

 tractile axis or myoneme, which is continuous with the body 

 ectoplasm. Notice that this myoneme is situated within the 

 sheath in a very loose spiral, and that the stalk quickly con- 

 tracts into a close spiral when the animal is stimulated. Ob- 

 serve also the manner in which the peristome folds over 



