Some Effects of Ultra Violet Radiation on Hydra.

In the following experiments an attempt has been made to determine the effects of ultra violet radiation upon Hydra, with respect to (1) physiological difference between species, (2) effects on budding, (3) effects of calcium chloride and magnesium chloride, (4) heat sensitization. All experiments were performed with a Pan Ray Arc lamp with an energy distribution of approximately 15 per cent ultra violet, 59 per cent visable, and 26 per cent infra red, with a total energy equivalent to 1 gm. cal. per sq. cm. per min. at 103 cm. 1 Each organism treated was exposed in a watchglass containing five centimeters of pond water, placed sixty centimeters from the arc. The total energy of the arc at this distance is 2.94 gm. cal. per sq. cm. per min. The temperature for each experiment was determined by immersing the thermometer in the watch-glass. For the heat sensitization experiments the water in the watch-glass was kept at a temperature which varied no more than 0.5° C. by the use of an electric fan.

Experiment I. Physiological difference between species: (A) Three species of Hydra were used: (a) H. viridis, (b) H. fusca, (c) H. dioecia. Six series of 6 specimens each were employed for the series of tests, making a total of 108 Hydra. Series 1 was left in pond water at room temperature; series 2 was exposed to ultra violet for 15 minutes behind a glass screen 3 mm. in thickness; series 3 was placed in an electric oven until the temperature was raised from 18° C. to 28° C., a rise of 2° C. more than that which occurred during any ultra violet exposure; series 4 was exposed 5 minutes and series 5, 10 minutes to ultra violet; series 6 was exposed 15 minutes to ultra violet. Series 1, 2, and 3 showed no change, all specimens of the three species remaining normal.