550 Journal of Agricultural Research voi. iv. No. e 



favorable than hay infusion. That the conditions in the solutions exam- 

 ined were unfavorable for the existence of these organisms is seen by the 

 fact that they did not appear until the twelfth to the fourteenth day, 

 while in others they did not develop throughout the entire period of 30 

 days. 



With the exception of solutions of hay infusion inoculated with green- 

 house and fertilized field soil, in all inoculations of both media greater 

 numbers of small ciliates developed at 15° to 16° C. than at any other 

 temperature, indicating that with these culture solutions this tempera- 

 ture is the most favorable for the development of small ciliates. With 

 every soil examined there was a much greater development of these 

 organisms in hay infusion than in blood extract. These facts indicate 

 that only certain types of small ciliates exist and develop at a definite 

 temperature and that the extent of their development is influenced by 

 the amount of desirable food and other favorable conditions in the cul- 

 ture solutions. Because of the fact that the development of small cili- 

 ates in dried-blood extract at 15° to 16°, 22° to 23°, and 29° to 30° C. 

 was not as great as in the solutions of hay infusion, the maximum num- 

 bers were in most cases developed sooner in the former than in the 

 latter solutions. At 15° to 16° C. in inoculated solutions of both media 

 the period of maximum development varied considerably. In the inocu- 

 lation of dried-blood extract with greenhouse soil the greatest numbers 

 were reached on the seventh day, while with the other soils a longer 

 time was required. The maximum development with the field-soil 

 inoculations was on the thirteenth day. With the fertilized field soil the 

 greatest number was not reached until the twenty-fifth day after inocu- 

 lation. In solutions of hay infusion with greenhouse soil the maxi- 

 mum number of organisms was reached on the thirteenth day, with the 

 fertilized field soil on the eleventh day, and with the field soil on the 

 nineteenth day after inoculation. 



Incubating at higher temperatures as a rule encouraged a more rapid 

 development of these organisms. However, this fact was not universal, 

 but it was noted that at the temperatures of 22° to 23° and 29° to 30° C. 

 the small ciliates began to appear at an earlier period than at lower tem- 

 peratures of inoculation. This fact is especially marked in the green- 

 house and fertilized-soil inoculations of both media. At 29° to 30° C. in 

 the greenhouse-soil inoculations the organisms appeared on the second 

 day, at 22° to 23° C. on the third day, at 15° to 16° C. on the fifteenth, 

 and at 6° to 7° C. in one inoculation on the twelfth day, and with the 

 other they did not appear until the twenty-seventh day. A very similar 

 circumstance was noted with the fertilized field soil, but in this case at 

 the highest temperature the organisms did not appear until the third 

 day, in solutions inoculated at 15° to 16° C. on the fifth to sixth day, 

 while in solutions inoculated at 6° to 7° C. they appeared on the four- 



