14 SOME MINUTE ANIMAL PARASITES 



claims of zoologist and botanist, but we follow the 

 lead of the authority on the subject, Dr. J. J. Lister, 

 F.R.S., whose standing in the zoological world is 

 beyond assail. 



A third great group of the Protozoa is the Masti- 

 gophora, which includes that vast array of organisms 

 known as the Flagellates. 

 Within this group are both 

 free-living and parasitic 

 organisms, some of them 

 being of high economic im- 

 portance. The chief char- 

 acteristic of the Flagellates is 

 their possession of a special 

 method of locomotion. Pro- 

 truding from the body of the 

 organism are one or more 

 long, vibratile threads termed 

 flagella (Fig. 2, fl.}. Each 

 flagellum is capable of rapid 

 movements, and by means of 

 its actions the progress of 

 these Protozoa is largely 

 brought about. Many of 

 the Flagellates possess two 

 nuclear bodies (Fig. 2, ., 6.), 

 the functions of which are 

 supposed to be different from 

 one another. In some Flagellata the limiting 

 layer of the body is prolonged outwards into a 

 finlike, propulsory structure known as an undula- 

 ting membrane. Much variation exists among the 



FIG. 2 A FLAGELLATE 

 PROWAZEKIA 



n., Nucleus; &., blepharo- 

 plast ; fl. , the two flagella 



