Effects of High Vacua and Extreme Temperatures on Cysts of Colpoda cucullus

Abstract

D URING the spring and summer of 1931, investigations were undertaken on the effects of extreme temperatures on highly desiccated cysts.2 Filter paper on which Colpoda cucullus had been induced to encyst was exposed to room humidity and temperature for several weeks and then cut into small rectangles. These rectangular pieces were carefully rolled, and to each piece was clamped a U-shaped segment of soft iron wire. Thereupon they were subjected for several days to high vacuum (about io-5 mm. Hg) by means of a mercury pump which was provided with a liquid-air trap and an ionization gauge. Small pyrex tubes were sealed alternately to either side of a large extension tube on the high vacuum side of the mercury pump and kept at high temperature (450 C.) during the 2 or 3 days of evacuation. Into these small tubes, after cooling, the rolled pieces of filter paper were introduced with the aid of a magnet. The tubes were then sealed off. Fifty-three such tubes which had been tested for high vacuum by means of an induction coil were placed from time to time into liquid air for periods from i hour to I21 days. After exposure, the tubes were broken and the small clamps were removed from the filter paper. These pieces of filter paper were thereupon immersed in balanced medium; and, with no exceptions, free-swimming Colpoda were observed in the medium in the course of several hours. Controls, of dishes and medium, were negative.