ONE-CELLE D ANIMALS— PHYLUM PROTOZOA 101 



The cycle is completed when the mosquito bites another person. 

 When the mosquito bites she injects a little saliva into the wound 

 which prevents the blood from clotting. This saliva will carry the 

 sporozoites into the body of the person which she is biting, and the 

 cycle begins again. 



Malaria control is one of the major health problems of the world 

 because of the widespread occurrence of this disease. There are many 

 regions of the world which are rich in resources, but remain undeveloped 

 because of the prevalence of malaria. Many of these are being opened 

 to development by a program to fight malaria. Since all mosquitoes 

 must pass the first part of their lives in water, most means of control 

 start there. Swamps can be drained or oiled and other bodies of water 

 can be kept well supplied with minnows which eat the eggs, larvae, 

 and any adults which may alight on the water. Sprays, such as DDT, 

 will help eliminate any of the adults that manage to survive. These 

 measures coupled with a campaign to find and treat those persons 

 carrying the malarial parasite will do much to eradicate the disease. 



Protozoa v/ith Cilia — The Ciliata 



Members of this class are found very abundantly in the water of 

 ponds and streams which is rich in decaying organic matter. They 

 can usually be cultured rather easily in the laboratory by placing 

 some dead grass or other leaves in pond water and allowing the mixture 

 to stand for a week or two. As the water becomes turbid with sus- 

 pended particles of decaying matter, the ciliates will usually be rather 

 abundant. All members of this class bear cilia on their bodies. Cilia 

 are very small hair-like structures which can beat back and forth 

 in locomotion. By controlling the beating of the cilia these organisms 

 can move in any direction without changing their body position. 



Paramecium is a good representative genus of this class which is 

 usually selected for laboratory study to illustrate a complex protozoan. 

 A number of different species are commonly available, but Paramecium 

 caudatum is probably used more than any other. It is found abundantly 

 in many ponds which are rich in organic matter. It is a slipper-shaped 

 animal with its body covered by a tough, yet flexible, pellicle. This 

 pellicle enables the Paramecium to bend its body, but it will return to 

 it original shape when it relaxes the bending force. The plasma mem- 

 brane lies under the pellicle. Cilia are embedded in the pellicle and 

 are arranged in the form of a spiral down the longitudinal axis of the 

 animal. This causes the paramecium to revolve and take a spiral 

 course through the water when swimming. A single animal will have 



