I lO PROTOZOANS 



by conjugation of a free swimming head with a stalked 

 head ? 



Draw several forms and show as much of the structure 

 as possible by the drawings. 



Compare Amoeba, Paramecium, and Vorticella, bringing 

 out especially the increasing complexity of structure. 



SUMMARY. 



One celled animals are not only simple and primitive in 

 form, but the life processes in them are carried on with 

 the least mechanism possible. As the entire cell is in con- 

 tact with the food medium, the organization for nutrition 

 is necessarily almost wanting. Yet there is a perceptible 

 increase in complexity as we go from the Amoeba to the 

 Vorticella. 



Other Common Forms : Protozoans are everywhere pres- 

 ent and furnish part of the environment in which all ani- 

 mals must grow. The number of species is very great 

 and they inhabit in countless numbers and conditions every 

 part of the known world. They are supposed to have 

 been the first forms of life on the earth, and during this 

 time they have developed many variations in form and mode 

 of life. 



Parasites : Many protozoans are parasitic in habit, their 

 size, and simplicity rendering them particularly well fitted 

 for such life. In the human body, the germ of disease which 

 causes dysentery, and the malarial parasite which by mul- 

 tiplying causes malarial fever, etc., are protozoans. Gre- 

 garinidcC are also parasites and live in the intestines of the 

 centipede, crayfish and other animals. 



Marine Forms : The water of the ocean, though clear in 



