8o 



C. L. HOOD. 



the zoochlorellae were innumerable. Artificial cultures were at- 

 tempted with little success. For this reason collections were 

 kept in the laboratory just as they were when taken from the 

 pool, except that fresh spring water was added daily. 



After thirty days specimens from these cultures showed a 

 decided decrease in the number of zoochlorellae. Fresh collections 

 were then made and treated as before with like results. It 

 was found that with such treatment Frontonia would, in from 

 thirty to forty days, be partially if not entirely free of zoo- 

 chlorellae. 



On September 15, 1925, seven cultures in fresh spring water * 

 were started, using Syracuse watch glasses as containers. Twelve 

 specimens were placed in each culture, and fresh spring water 

 was added daily. By September 18 approximately fifty per 



FIG. i. Camera lucida drawings. X 375. A, normal specimen taken on 

 date of collection. B, after twelve days in fresh spring water. C, after twenty- 

 five days in fresh spring water. D, after forty days in fresh spring water. 



cent, of the total number of the specimens had disappeared. 

 September 21, all specimens had disappeared from five cultures. 



1 Analysis of the spring water was made by Mr. R. K. Witt, under the direction 

 of Dr. John H. Yoe of the Department of Chemistry, University of Virginia, and 

 showed the following: 



Parts Per Million. 



Total solids 37.6 



Fixed residue 28.0 



Loss on ignition 9.6 



Organic matter Very small amount as 



indicated by a slight 

 charring on ignition. 

 The pH value of the spring water was fairly constant at 7.2. 



