In August of last year I was in South Uist on an angling expedition, and, while fishing one of the lochs on the island, my attention was drawn to some very remarkable balls that were lying in great numbers at the bottom. I examined a good many of these, and found that they were composed of innumerable algal filaments so intertwined and matted together as to form an outer covering of an almost felt-like consistency, which could, however, be torn open without difficulty. This outer coating varied (speaking very roughly) from about a twentieth to two-twentieths of an inch in thickness, or even more, and the interior of the balls consisted, so far as the naked eye could see, only of mud. The microscope, of course, tells a different story.