804 SOIL PKOTO/.OA IX SOUTH AFRICA. 



(8) Another similar culture in a flask of 62'5 mm. diameter, 

 made at the same time and examined at the same time as. the 

 other cultures, showed a still further increase, the Protozoa found 

 in one-half c.c. of the culture being: — 2 Amoeba proteus, 1 

 Difjlugia pyrifonnis, 1 Hyalosphoiia clegans, 8 Euglypha sp., 13 

 Musfigamoeba sp., 00 Plcuroninnas jacitlcDis and ol Cyclidinrn 

 g] an coma. 



From this experiment, it seems possible that shallow cultures 

 of soil are likely to yield more Protozoa quickly than deep 

 cultures, perhaps due to better aeration, but the matter is under 

 further investigation by us, and the present statement is 

 tentative. 



Effect of Light 



In continuation of our previous experiments (see this 

 Journal, XVIII, p. 388), some parallel cultures of soil were kept 

 in the light and in a dark, well ventilated cupboard respectively, 

 and were examined daily. Light and darkness appeared to have 

 very little influence on the development of the contained Protozoa, 

 as the same organisms appeared in each culture on the same day. 



However, one interesting effect was noticed in the case of 

 Hyalosphenia clegans, from a culture of Stellenbosch soil reported 

 on last year. When cultures containing this organism 



and kept in the dark were examined, it was noted that some- 

 times the organism put out pseudopodia, which was very seldom 

 seen in Hyalosphenia from a culture kept in the light. This, 

 perhaps, was a response to the sudden stimulus of light. 



The Distpjbutiox of Protozoa i.\ the Culture Fluid. 



It has been stated by some American workers that certain 

 Protozoa occiu' in all parts of the culture fluid. It may be of 

 interest to note the distribution as found in some cases of soil 

 cultures in South Africa. New cultures were made for these 

 experiments, and sails were used that were known, from our 

 previous experience, to be relatively rich in Protozoa. The 

 culture tubes contained one inch of soil, above which were three 

 inches of water, making a depth of four inches in all. The areas 

 of the culture tube are designated surface film, middle layer, and 

 soil layer respectively. A few typical results may be cited: — 



(1) Cultiu-e of soil from St. James. 



Surface film. — Many Amoeba prnfeus, a few Mastiga}iio'})a 



sp. 

 Middle layer. — Negative for Protozoa. 

 Soil layer. — Very few Amoeba proteus. Mastigamoeba sp., 



Euglypha sp., Cyclidium gJaucoiita. 



(2) Culture of soil from Heathfield, C.P. 



Surface film. — A)noeba proteus, fairly numerous Plevro- 



monas jacuJans. 

 Middle layer. — V.ery few PJeuroi)io)ins jacidans. 

 Soil layer. — Very few Amoeba proteus, Pleuromonas 



jarulans. Cyclidium glaucoma . 



