Effects of ultraviolet light (2535 A) and dactinomycin upon hydra (Pelmatohydra oligactis)

Hydras exposed to ultraviolet light (2535 A, 12 erg/mm-2/s-2) for 15 minutes suffer a depression immediately, individuals that survived recover quickly and lastingly. Hydras treated with dactinomycin of specific concentrations do not suffer a depression until several days later, do not recover and die eventually. The results are also comparable when hydras are exposed to light and treated with cytostatic of such concentration. In even milder solution of dactinomycin all unexpected hydras recover and survive. But, almost all of the hydras exposed to ultraviolet light and treated with this solution die eventually. The effect of ultraviolet light upon them is then distinctly adverse. Buds are much less damaged and they do not die in this concentration. They grow and reproduce normally. This paper deals with the above mentioned phenomena.