196 SCIENCE FROM AN EASY CHAIR 



ducers of food currents driving the food right in to a 

 permanent, definitely-shaped mouth. Some have also a 



FIG. 41. Two specimens of a bell-animalcule (VorticelZa). A, extended. 

 B, with retracted disc and coiled stalk, a, the ciliated disc ; b, the firm 

 ring behind the disc, called "peristome"; c, the pulsating chamber, 

 called often the contractile vacuole ; d, a completely digested particle of 

 food on its way to be cast out through the gullet ; e, the sausage-shaped 

 nucleus ; /, a particle of food which has just sunk into the protoplasm 

 from the gullet, and is surrounded by a little water ; g, the gullet ; A, the 

 reservoir leading from the pulsating chamber to the gullet ; i, the hollow 

 stalk ; k, the spirally attached muscle within the stalk ; /, the attachment 

 of the stalk to a weed m. 



separate opening by which the undigested remains of the 

 food are extruded. They have also a liquid-holding 



