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LABORATORY MANUAL OF MICROBIOLOGY 



4. Protozoa. — Many of these organisms feed upon bacteria, 

 and their development depends upon the abundance of bacteria. 

 Some of the protozoa, hke the ciUates and amoebae, are large in 

 size, and they may form a considerable quantity of living or 

 recently living protoplasm in the soil. The protozoa are repre- 

 sented in the soil by the (a) flagellates, (b) amoebde, and (c) ciliates 

 which are usually less numerous than the other two groups. 



5. Invertebrate Population of Soil, Non-protozoan in Nature. — 

 This group is represented in the soil by the (a) Nematodes, or 

 round worms, which may be present in hundreds of millions per 

 acre of soil, (b) Rotifers or wheel animalcules, (c) Turbellarians, 

 or flat worms, (d) Trematodes, or flukes, (e) AnneUds or seg- 

 mented worms, including the earthworms, (/) Arachnids, includ- 

 ing the mites, ticks, and spiders, (g) Myriapodes, (h) insects, etc. 



The relative abundance of these organisms per gram of soil 

 can be shown as follows : 



