ix.] THE BELL-ANIMALCULE. 95 



2. In the retracted state. 



a. The body. 



a. Its form; pear-shaped; rounded off above; no 

 disc or peristome visible. 



{3. The clear transverse space near the top, indi- 

 cating the interval between the retracted disc 

 and the rolled-in peristome. In this space 

 the cilia can frequently be seen moving. 



y. Structure; as in i. a. c. 



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



3. The movements of Vorticella. Compare especially 

 the regularity, defmiteness and rapidity of some of 

 them with the slow and irregular movements of 

 Amoeba. (III.) 



a. The ciliary movement. 



a. Examine the cilia carefully; delicate homo- 

 geneous processes; their length, diameter and 

 form ; their position. 



[/3. The continuity of the cilia with the cortical layer.] 

 y. 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 movements of the contractile vesicle (see III. 

 A. 3. c). Tolerably regular rhythmic distension 

 and collapse (diastole and systole). 



