336 PRINCIPLES OF SOIL MICROBIOLOGY 



inside mouth. The following organisms belonging to this group 

 were found in the soil: Blepharisma ovata by F, JB. laterita by J, 

 Metopus sigmoides and Metapides acuminata by F, Spirostomum 

 ambiguum by I, Condylostoma sp. by Koch. 



III. Oligotricha. Spherical or conical, with adoral zone often form- 



ing a closed ring; cilia usually absent from other parts of body. 

 The following forms were recorded as present in the soil: 

 Strombidium sp. by E, F and I, Halteria grandinella by A, F, I 

 and K. Other species of Halteria were found by B, E, J and N. 



IV. Hypotricha. Body flattened dorso-ventrically; cilia often fused 



to form larger appendages or cirri, usually limited to ventral 

 surface; adoral zone of membranellae. This group is represented 

 in the soil by Urostyla grandis (C, K), Stichotricha secunda (F), 

 Uroleptus musculus (A, F, K and Koch), U. mobilis (J), U. piscis 

 (I, J), U. dispar (F, I, N), Onychodromus grandis (J and other 

 investigators), Gastrostyla steinii (C, J), Gonostomum (Plagio- 

 tricha) affine (C, J, K, L, M), Oxytricha fallax (J), 0. bifaria (F), 

 0. pellionella (Cunningham and Lohnis, F, I, J); other species 

 of Oxytricha were also found by different investigators of soil 

 protozoa. Pleurotricha lanceolata and P. grandis (C, J), Sty- 

 lonychia mytilus (B, F, I), S. pustulata (F, K), Euplotes carinata 

 (F, J), E. charon (A, F, J), E. harpa and E. patella (I), Aspidisca 

 coslata (F, I, K) and A. lyncaster (K). 

 V. Peritricha. Body cup-like or cylindrical, often stalked, of a 

 sedentary habit; cilia usually limited to adoral zone, the mem- 

 branellae leading down to a vestibule, into which pharynx and 

 contractile vacuoles open; a posterior ring of cilia may be tem- 

 porarily present. This group is represented in the soil by Vorti- 

 cella microstoma (C, F, J, K, N), V. citrina and V. globularia 

 (F), V. nebulijera (K, N), V. putrina (A, F); other species of 

 Vorticella have also been found by different other investigators. 

 Epislylis coarctata (C), Cothurnia doliolum (B), Vaginicola ter- 

 ricola (B). 



Importance of protozoa in the soil. No definite evidence has as yet 

 been submitted as to the actual role of protozoa in the soil. We know, 

 on the one hand, that certain groups of protozoa at least, particularly 

 the ciliates and amoebae, are not only capable of ingesting bacteria, but 

 some actually use this sort of food exclusively. 9091 By determining the 

 number of amoebae and bacteria in the soil, at daily intervals, an inverse 

 relationship has been obtained between these two groups of organisms. 



90 Huntemtiller, O. Vernichtung von Bakterien im Wasser durch Protozoen. 

 Arch. Hyg., 54: 89-100. 1905; Calkins, 1926 (p. 312); Purdy and Butterfield, 

 1918 (p. 322) ; Cunningham, A. Studies on soil protozoa. Tour. Agr. Sci., 7: 49- 

 74. 1915. 



91 Cutler and Crump, 1920 (p. 50). 



