The Long Wave-Length Limit of Photolethal Action in the Ultra-Violet

Abstract

Paramecium mul-timicronucleata, Stylonychia mytilus and Euplotes patella were not killed, nor even noticeably affected, by long irradiation with intense u.v. ([lambda] 3130A), though they were readily killed by much lower doses at 3025A. (The dosage for Paramecium was such as to give approximately equal absorption at the 2 wave-lengths.) These organisms are apparently adapted to 3130A, which is present in relatively high intensity in sunlight.