W. T. BOVIE AND ALICE KLEIN 333 



Total No. of organisms radiated 60 



No. of deaths 



Per cent of death 



Experiment 1 shows that with the Hght intensities used, an expos- 

 ure of 4 seconds to fluorite rays is not sufficient to cause death of the 

 organism. 



Experiment 2. Effect of Extra Manipulation of Placing on a Tem- 

 perature Slide and Then Exposing to Heat. — Organisms were radiated 

 for 4 seconds at 17-18°C., and then exposed on a temperature sHde 

 to 16-1 7°C. for 60 seconds. 



Total No. of organisms radiated 30 



No. of deaths 3 



Per cent of death 10 



We had observed that some of the radiated organisms appear to 

 be sticky and It was thought that a certain per cent of the deaths in 

 Experiment 5 might be due to accidental physical injury incurred 

 during the transfer to and from the temperature shde. Experiment 

 2 gives the result of an investigation of this question. 



Experiment 3. Effect of Heat Alone. — Unradiated organisms were 

 exposed on a temperature slide to 24-28°C. for 60 seconds. 



Total No. of organisms 21 



No. of deaths 



Per cent of death 



The results obtained in Experiment 3 were to be expected. They 

 are in agreement with those of Woodruff and BaitselP on the tempera- 

 ture coefficient of the rate of reproduction of Paramecium aurelia. 

 According to these authors the optimum temperature zone for repro- 

 duction is between 24° and 28.5° C. 



Experiment 4. Effect of Heating First and Then Radiating. — Or- 

 ganisms were exposed on a temperature slide to 24-26°C., for 60 

 seconds, and then radiated for 4 seconds at 17-18°C. 



Total No. of organisms radiated 52 



No. of deaths 4 



Per cent of death 8 



5 Woodruff, L. L., and Baitsell, G. A., The temperature coefificient of the rate 

 of reproduction of Paramcecium aurelia, Am. J. Physiol., 1911-12, xxix, 147. 



