8 4 



C. L. HOOD. 



TABLE I. 



SHOWING HYDROGEN ION CONCENTRATION OF THREE COLLECTING POOLS 

 OVER AN EXTENDED PERIOD OF TIME. 



A from pool containing Frontonia with no zoochlorellse. 



B with relatively few. 



C in which the zoochlorellas were innumerable. 



Beginning June 20th there were increasing rains until July 10. On July 12 

 collections were taken from all pools where Frontonia had previously been found 

 and a uniform scarcity of zoochlorella? was observed. 



As stated above, when specimens containing relatively few 

 zoochlorellae are placed in cultures and left undisturbed, so 

 that the culture medium becomes somewhat stagnant, the zoo- 

 chlorellae increase very noticeably. Also that when specimens 

 containing numerous zoochlorellae are changed from their original 

 culture to a medium of fresh spring water, the zoochlorellae 

 decrease very noticeably. There is correlated with this increase 

 and decrease in the number of zoochlorellae, an increase and 

 decrease in the hydrogen ions. The following examples are 

 characteristic of the finding in this respect. 



A collection in which the Frontonia showed relatively few 

 zoochlorellge had a pH value of 7.3. This culture remained in 

 the laboratory and the hydrogen ion concentration was taken 

 every other day until the specimens harbored innumerable zoo- 

 chlorellse, thirty days. Data thus obtained are given in Table II. 



TABLE II. 



SHOWING VARIATIONS IN pH VALUE OF THE MEDIUM AS THE NUMBER OF 



ZOOCHLORELLiE INCREASED. 



June and July, 1926. 



