92 ELEMENTARY BIOLOGY. [iX. 



j8. The clear transverse space near the top, indica- 

 ting the interval between the retracted disc 

 and the rolled-in peristome. In this space the 

 cilia can frequently be seen moving. 



7. Structure ; as in 1. a. c. 

 b. The stalk ; thrown into corkscrew-like folds. 



3. The movements of Vorticella. Compare especially 

 the regularity, definiteness and rapidity of some of them 

 with the slow and irregular movements of Amwha. 

 (III.) 



a. The ciliary movement. 



a. Examine the cilia carefully; delicate homoge- 

 neous processes ; their length, diameter and 

 form ; their position. 

 [/i. The continuity of the cilia with the cortical layer.] 

 7. The function of the cilia; their rapid move- 

 ments, alternately bending and straightening ; 

 the co-ordination of these movements ; they 

 work in a definite order ; note the currents 

 produced in the neighbouring water (if ne- 

 cessary introduce a few particles of carmine 

 under the coverslip); the sweeping of small 

 bodies down the gullet. 



b. The movem,ents of the contractile vesicle (see III. 

 A. 3. c). Tolerably regular rhythmic distension 

 and collapse (diastole and systole). 



c. The currents in the central parts of the body carry- 

 ing round the swallowed bodies. (Compare VI. C.) 



d. The movements of the animal as a whole. (-^ inch 

 or \ inch obj.) 



