MONOCELLULAR ANIMALS-THE PROTOZOA 



115 



In order to discover how the ciHa operate 

 in such perfect coordination, biologists have 

 made careful studies of the mechanism in- 

 volved. It has been found that the cilia 

 are attached to one another by tiny fibrils 



ments. Clearly something similar to the 

 nervous system in multicellular animals ex- 

 ists in Paramecium, which makes it possible 

 for this tiny cell to carry on in such a com- 

 plicated manner. 



contractile vacuole 

 food vacuole 

 trichocyst 



cilium 



oral qroove 



micronucleus 



macronucleus 



cytostome 



ectoplasm 



endoplasm 



pellicle 



canal of c. vacuole 



cytopyqe 



Fig. 7-7. Paramecium with internal parts shown in detail. 



just beneath the pellicle. The fibrils con- 

 centrate at a focal point in the region of 

 the gullet where the protoplasm must form 

 the equivalent of a miniature "brain." If 

 this is destroyed experimentally, the cilia 

 fail to beat in a coordinated manner, and 

 the animal loses all control of its move- 



Ingesting of food 



A simple experiment can be performed 

 to demonstrate how paramecium feeds. 

 Some yeast cells that have been heavily 

 stained with Congo red ( a dye ) are placed 

 on a glass slide containing a drop of para- 



