556 Journal of Agricultural Research voi. iv. No. 6 



DEVELOPMENT OF THE DIFFERENT TYPES OF SOIL PROTOZOA 



That the temperature influences the development of the different types 

 of soil protozoa in culture solutions is shown by the fact that the numbers 

 of the different species developed varied a great deal. The forms studied 

 tallied best with the descriptions of Colpoda cucidlus, Colpidium colpoda, 

 Vorticella spp., Prorodon ovum, and Glaucoma sp. They appeared in 

 some of each series of solutions incubated at 15°, 22°, and 29°. Of these 

 organisms Colpoda cucullus was the only one that developed at 6°. At 

 this temperature only a few appeared on the fourteenth day, and these 

 were present until the twentieth day. Other ciliates that developed at 6° 

 were Paramecia spp. At 15° Colpoda cucullus was the most numerous 

 form of the ciliate type. These first appeared on the sixth day and 

 were present throughout the experiment. Incubating at 15° was not 

 very favorable for the development of the vorticellae. They appeared 

 on the fifth day and were still seen on the thirtieth day after incubation. 

 Besides species of Colpoda, Vorticella, Prorodon, and Glaucoma, long 

 slender ciliates, possibly Condylostoma patens Miill., were very numerous 

 at 22° and 29°. At 22° species of Vorticella, Colpoda, Prorodon, and 

 Glaucoma appeared on the third day. The vorticellae were present until 

 the twenty-sixth day after inoculation, while the other forms were still 

 seen on the thirtieth day. The temperature of 29° was more favorable 

 for the development of Colpoda cucullus, Prorodon ovum, and Glaucoma 

 sp., but at this temperature many vorticellae were also developed. This 

 last-named form appeared on the second day and was noted until the 

 fifteenth day after inoculation. The most prominent flagellates were 

 species of Monas and Bodos. 



As previously noted in Part III, all the small ciliates do not encyst 

 when the conditions become unfavorable. This was again noted, for in 

 the solutions incubated at 29° many dead individuals of Prorodon ovum 

 and Glaucoma sp. were seen* on the seventh day after inoculation. 



The higher temperatures of incubation were the most favorable for 

 the early excystment of small ciliates. 



That the Vorticella cysts are present in field soils which have received 

 applications of manure is shown by the fact that these organisms devel- 

 oped in culture solutions inoculated with the fertilized soil. The num- 

 bers, however, were very small as compared to those developed in solu- 

 tions inoculated with greenhouse soil. 



Upon several occasions during the examination of the solutions an 

 individual of Colpoda cucullus was seen in the process of being excysted. 



The conditions under which this experiment was carried out seemed 

 to be unfavorable for the development of amoebae, as none of these organ- 

 isms developed in any of the media employed. 



