Sept. 15, 191S 



Soil Protozoa 



519 



what might appear to be protozoa. For this reason all of the protozoan 

 counts were made under the low power. In order that the results might 

 be concordant, every culture was examined about the same hour each 

 day, for there is a great variation in the numbers of active organisms 

 present at different hours during the day (Table VI). This is especially 

 true for the first 10 to 15 days after inoculation. 



Table VI. — Variation per grain 0/ soil in numbers of protozoa present in culture solutions 

 at different hours of the same day 



Culture No. 



721 

 722 



723 

 724 



Second day after inoculation. I Third day after inoculation. 



3,272,000 



6, 180, 000 



505, 000 



221, 400 



5, 430, 000 



7, 220, 000 



I, 117, 000 



585, 000 



16, 800, 000 



6, 980, 000 



798, 000 



516, 000 



9, 982, 000 



5,950,000 

 610, 000 

 221, 400 



DEVELOPMENT OF PROTOZOA IN DIFFERENT CULTURE SOLUTIONS INOCU- 

 LATED WITH VARYING AMOUNTS OF MOIST AND DRY SOIL 



Small ciliates. — The development of protozoa in the various solutions 

 was quite different (as shown in Table VII). In comparing the develop- 

 ment of the small ciliates in different media, it is apparent that the maxi- 

 mum development of these organisms occurred sooner in dried blood than 

 in soil extract. In all inoculations of the dried-blood extract the greatest 

 numbers were present on the third to the fourth day ; the numbers then 

 decreased, so that after the ninth day there were very few present through- 

 out the remaining period of obser^^ation. In soil-extract solutions inocu- 

 lated with the largest amounts of soil, the maximum development was 

 from the third to the fourth day, whereas in solutions of the same extract 

 inoculated with 1 gm. of dry soil they did not appear until the ninth day 

 and on the sixteenth day with the same amount of moist soil. In both 

 culture solutions the numbers of small ciliates developed were very small 

 as compared with the number of flagellates. For the existence of small 

 ciliates the soil extract seemed to be more favorable than dried blood. 

 In comparing the numbers of organisms developed in the different solu- 

 tions it was found that those which were inoculated with the largest 

 amounts of soil did not show greater development than the ones to 

 which the smallest amounts of soil had been added. Hence, on the 

 gram basis more than a hundred times as many small ciliates developed 

 from I gm. of soil as from 100 gm. It is noted that in nearly all inocula- 

 tions of both media a greater number of organisms developed at an 

 earlier period from the moist than from the dry soil. This difference 

 was, however, not very great. 



