VII.] THE BELL-ANIMALCULE. 367 



the coiling up of the stalk ; the rolling in of the 

 disc. The rapidity of these movements. 



y. The mode of re-expansion ; the stalk straightens 

 first ; then the peristome is everted ; finally the 

 disc and its cilia are protruded. 



4. Stain with iodine or magenta ; the cuticle uncoloured 

 — the rest stained; the nucleus especially becomes 

 deeply coloured. 



5. Treat with acetic acid; the contents soon disappear 

 (except perhaps some swallowed bodies) — the cuticle 

 later or not at all. 



6. Look for the following in various specimens — 



a. Multiplication by fission.^ early stage ; a bell par- 

 tially divided into two by a vertical fissure start- 

 ing from the disc. 



^. The same, late stage ; two complete bells on one 

 stalk ; the result of completion of the fission. 

 The development of a basal circlet of cilia by 

 one or both of these bells. 



y. Free swimming unstalked bells (detached bells 



from P). 

 8. Conjugation; the attachment of a small free 



swimming bell to the side of a stalked one. 



€. Encystation ; the body contracted into a ball 

 and surrounded by a thickened structureless 

 layer, the contractile vesicle being persistently 

 dilated. 



B. Other forms closely allied to Vorticella which may be 

 met with, and which will do nearly as well for exami- 

 nation, are ; — 



