VORTICELLA. 



Vorticellidse are found both in fresh and salt water, adhering to plants, insects, 

 &c., and when present in considerable numbers appear to the naked eye as little 

 white tufts. 



A. Eemove a small piece of weed to which the Vorticellse are attached, place in a 

 drop of water on a slide, lay a piece of moistened writing paper near the weed, and 

 apply a covering glass. Examine with low power, and note — 



1. That the colony is composed of a number of individuals, each of which 



has a beU-shaped body, supported at its narrow end on a stem. 



2. That this stem is constantly being retracted in a spiral form. 



3. That during retraction of the stem, the body assumes a spherical form, by 



the margin being bent closely inwards. 



4. In addition look for — 



(a) Specimens in process of budding. 



(b) The small free swimming buds. 



(c) The buds conjugating with adult fixed forms. 



(d) Specimens in process of division by longitudinal fission. 



(e) The half which becomes free, noting the posterior circlet of cilia 



which exists during its free-swimming stage. 



B. Examine under high power, and notice — 



1. That the bell has the margin bent outwards, forming a thickened edge (the 



peristome), and that it is vertically striated near the base. 



2. That this peristome bears cilia. 



3. That there is a ciliated disk-shaped portion — the epistome — filling up most 



of the mouth of the bell. 



4. That at one point a space — the vestibule — is left between the peristome 



and epistome, and that there is a narrow pharynx continuous with the 

 vestibule. 



5. The stem, consisting of — 



(a) An outer generally straight sheath, and 



(6) A central striated portion, which has a slight spiral form within the 

 outer sheath. 



6. That on irritation the epistome is retracted, while the peristome is folded 



closely over it, so that the body assumes a rounded form, which is fol- 

 lowed by the retraction of the body by the stem throwing itself into a 

 spiral form. 



7. That the body consists of cuticle, clear ectosarc, and granular endosarc. 



8. The contractile vacuole near the upper edge of the bell. 



9. That food vacuoles are present, and that they circulate slowly down one 



side and up the other. 



C. Place a few particles of powdered carmine near the vorticellse and notice that 

 the cilia sweep them into the vestibule, near the bottom of which they are aggregated 

 into a food vacuole. 



D. Add to the preparation acetic acid or a staining fluid, and note the horse- 

 shoe-shaped nucleus. 



