312 PRINCIPLES OF SOIL MICROBIOLOGY 



classification, and physiology of protozoa is found elsewhere. 4-8 Some 

 of the information, necessary for a knowledge of the identification and 

 study of activities of soil protozoa, is given here. 



Protozoa are unicellular organisms, varying in size from a few microns 

 to 4 to 5 cm. Some protozoa may also form colonies consisting of 

 numerous individuals. The majority of species, particularly the soil 



4 Biitschli, O. Protozoa. In Bronn's Klassen und Ordnungen des Thier- 

 reichs. 1, 1883. 



6 Doflein, F. Lohrbuch der Protozoenkunde. 4th Ed., Jena, 1916. 



6 Minchin, E. A. An introduction to the study of protozoa. Arnold, Lon- 

 don. 1912. 



7 Edmondson, C. H. The protozoa of Iowa. Proc. Davenport Acad. Sci., 

 12: 1-124. 1906. Schaeffer A. A. Taxonomy of the amebas, with descrip- 

 tions of thirty-nine new marine and freshwater species. Dept. Marine Biol. 

 Carnegie Inst., Washington, 24. 1926. 



8 Calkins, G. N. The biology of the protozoa. Lea & Febiger, Philadelphia. 

 1925. 



PLATE XVII 

 Soil Protozoa 



128. Naegleria gruberi: a, small organism (8 to 3G>) with one broad blunt 

 pseudopodium or sometimes several blunt ones, and one subcentral nucleus. 

 When it enflagellates the karyosome sends out a chromatic process b, which tra- 

 verses the nuclear membrane, forms a marginal blepharoplast, and emerges as 

 two long flagella (c, d). The body assumes a rigid asymmetrically curved shape 

 and the organism swims away in the typical spiral course. When it exflagellates 

 the flagella shorten, thicken and retreat into the cytoplasm and the blepharo- 

 plast returns to the karysome within the nucleus (from Kofoid). 



129. Vahlkampfia soli, a Umax amoeba, from fresh fixed film (from Martin and 

 Lewin). 



130. Amoeba cucumis, a lamellipodian amoeba (from Martin and Lewin). 



131. Euglypha sp., a thecamoeba (from Martin and Lewin). 



132. Cyst of Amoeba cucumis (from Martin and Lewin). 



133. Colpoda steinii, X 800 (from Goodey). 



134. Balantiophorus elongatus, X 800 (from Goodey). 



135. Pleurolricha grandis (?), X 410 (from Goodey). 



136. Gonostomum affine, X 510 (from Goodey). 



137. Vorticella microstoma, living stalked form, X 410 (from Goodey). 



138. V. microstoma, free swimming, recently excysted form with aboral ciliary 

 ring, X 510 (from Goodey). 



139. Bodo caudatus (from Martin and Lewin). 



140. Monas guttula (from Fellers and Allison). 



141. Cercomonas crassicauda (from Fellers and Allison). 



142. Bodo ovatus (from Fellers and Allison). 



143. Pleuromonas jaculans (from Fellers and Allison). 



