Cytochrome-catalysis of the movements of bracken spermatozoids

The movements of bracken spermatozoids are photo-reversibly inhibited by carbon monoxide. At 20° C the mean speed of a sperm suspension in the presence of 94% CO in O2 was 51 μ/sec, in green light, the wave-length of which is outside the region of photochemical absorption by CO-cytochrome oxidase. The same suspension had a mean speed of 95 μ/sec. in white light. Spermatozoids that have been rendered motionless by CO in green light, which takes about 5 min., can be induced to move by illuminating them with white light. A large percentage of the spermatozoids are irreversibly damaged if the CO in green light treatment is continued long enough to stop, rather than slow up, movement.