SOILS FERTILIZERS. 21 



can be transferred by a platinum wire loop to the ruled area of a clean glass 

 slide. 



Comparing the development of protozoa in artificial culture solutions of 

 different kinds, inoculated with varying amounts of soil, with moist and dry 

 soils, and with different kinds of greenhouse soils, it was found that the maxi- 

 mum development of small and large ciliates and flagellates in dried-blood 

 extract was from the third to the fourth day, while in soil extract it was from 

 the second to the fifteenth day, depending upon the character and amount of 

 soil used for inoculation. The soil extract seemed to be the more favorable 

 medium. When the maximum development of all organisms was reached, there 

 was a gradual decrease in numbers until very few active forms were present. 

 The most rapid development of protozoa occurred in the culture isolutions inocu- 

 lated with the largest quantities of soil. Per gram of soil, there was the greatest 

 development from the least amount of soil used. The flagellates were the first 

 organisms to excyst and developed in greatest numbers. Drying the soil slightly 

 favored the development of flagellates in soil extract, while with dried blood 

 there was little difference. More large and small ciliates developed from the less 

 composted soils. In dried blood more flagellates developed from the more heavily 

 manured soils. Very many different types of ciliates were present, while the 

 types and numbers of amebfe were few. 



In further studies of the development of protozoa in different culture solu- 

 tions with varying amounts of soil inoculations and to compare the numbers 

 and types of protozoa developed from compost and field soils, it was found " that 

 in developing protozoa from the soil in artificial culture solutions different 

 numbers and types of protozoa will be developed for every variation in the 

 amounts of each soil used for inoculation and with every culture solution used." 



Experiments dealing with the numbers and types of soil protozoa appearing 

 at various temperatures in artificial culture solutions inoculated with soils of 

 different origin showed that a temperature of 15 to 16° C. was the most favor- 

 able for the development of small ciliates, hay infusion being the most favorable 

 culture solution at this temperature. The maximum development of small 

 ciliates occurred earlier in dried blood than in hay infusion, varying at 6 to 7" 

 from 17 to 30 days after inoculation and at 15 to 16° from 7 to 25 days after 

 inoculation. Large ciliates developed at all the temperatures noted. The 

 maximum development of flagellates occurred at 6 to 7° in dried-blood extract 

 and at 15 to 16° in hay infusion. DMed-blood extract and hay infusion were 

 unfavorable media for the development of large ciliates, while hay infusion was 

 the most favorable medium for the maximum development of flagellates. As 

 with the small ciliates, the higher temperatures encouraged and the lower tem- 

 peratures retarded the early development of flagellates. At all temperatures 

 the flagellates developed sooner than the ciliates, appearing 4 or 5 days earlier 

 at 15 to 16°. Species of Vorticella, Colpoda, Prorodon, and Glaucoma devel- 

 oped at 15 to 16°, at 22 to 23°, and at 29 to 30°, the last temperature being 

 very favorable for the development of the last three types. A few individuals of 

 Colpoda and Paramecium developed at 6 to 7°. At 15 to 16° Colpoda was the 

 most numerous ciliated form. Vorticella cysts were present in field soils which 

 had received applications of manure. Hay infusion and dried-blood extract were 

 unfavorable media for the development of amebse. 



General conclusions drawn from the experiments are that the development of 

 soil pi'otozoa in artificial culture solutions varies (1) with the kind of media 

 employed, (2) the quantity of soil used for inoculation, (3) drying of the soil, 

 (4) different kinds of soil and different soils of the same kind, and (5) the 

 temperature of incubation. 



A list of references to literature bearing on the subject is appended. 



