IX.] THE BELL-ANIMALCULE. 93 



a. | Its extreme irritability; it contracts on the 

 slightest stimulation: often without any ap- 

 parent cause. 



ft. The movements which occur in contraction ; 

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

 disc. The rapidity of these movements. 



7. 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. Note the following points in various specimens 



a. Multiplication by fission; a bell partially divided 

 into two by a vertical fissure starting from the 

 disc. 



/?. 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 



[8. Conjugation ; the attachment of a small free swim- 

 ming bell to the side of a stalked one.] 



[e. Encystation ; the body contracted into a ball and 

 surrounded by a thickened structureless layer, the 

 contractile vesicle being persistently dilated.] 



