Phosphorescence in Fish

Abstract

I HAVE noticed the phosphorescence in fish on two occasions. Once on a calm night, wind light and sea smooth, in the S.E. trades, lat 18° S., a shoal of porpoises was playing about under the bows of the ship, and darting under her keel for a space of nearly half an hour. Each looked like a piece of burnished silver on blue velvet. They presented the most beautiful appearance. We were not within “soundings.” Every wavelet was covered with phosphorescence during the whole of that night, before and after the porpoises were seen. They manifestly could not have been the cause of this. As I leaned over the side and watched them, it seemed to me that their phosphorescence re-suited from the condition of the water. Off the coast of South America, in about lat. 22° S., long. 30° W., weather much the same, a small shark accompanied the ship for some time, and presented the same appearance. The sea was brilliantly phosphorescent. The fish could be seen deep down. In both cases I saturated paper with the sea water. When dry the microscope failed to detect any organic matter, nothing but crystals.