362 JULIA ELEANOR MOODY 



In the interval between March 13 and March 23, there was a 

 sudden and marked mcrease, the number of divisions averaging 

 3.1 per day. Diagram 1 was made according to the method 

 of Calkins. The curve represents the general vitality of the 

 three lines through 218 generations, from February 24 to July 

 7, 1911. Woodruff defines a rhythm as "a minor periodic rise 

 and fall in fission-rate due to some unknown factor in cell metab- 

 olism from which recovery is autonomous" and in summing 

 up his paper on ''Rhythms in the reproductive activity of In- 

 fusoria" he concludes ''that it is not possible by constant envir- 

 onmental conditions to eliminate the rhythms and resolve the 

 graph of the multiplication into an approximately straight line." 

 Spathidium, cultivated under constant environmental conditions 

 except for slight variations in the temperature, showed distinct 

 rhythmic fluctuations as indicated by the curve in diagram 1, 

 which result is in close accord with those obtained by Gregory 

 ('09) in a study of the life-history of Tillina magna. The de- 

 crease in fission rate, followed by the death of the series; may 

 have been due to a difference in the salt content of the water. 

 From February 24 to June 6 Croton tap-water wsis used, but 

 from the latter date to July 7 spring water was substituted. 

 After March 23 there occurred a sudden decrease in the vitality 

 followed by high division rate from April 2 to April 30. From 

 this time on there was a gradual trend downward as indicated 

 in the diagram. 



On June 6, the entire stock was in poor condition as indicated 

 by the low division rate. On this date the individuals were 

 transferred to fresh hay-infusion to which Colpidium in abun- 

 dance had been added. Spathidium was sluggish and although 

 it continued to feed, it showed no improvement. Stimulation 

 with beef-extract was tried. At the end of an hour, one out of 

 six had died, and those which survived showed little improve- 

 ment. At the end of the second hour these individuals showed 

 a return to their normal condition and were transferred from 

 the beef-extiact to tap-water then to hay-infusion contaming 

 a few Colpidia. Although the individuals were normal in ap- 

 pearance, the division rate remained low. 



