Societies and Academies

Abstract

CAPE TOWN. Royal Society of South Africa, July 17.—Dr. A. Jasper Anderson in the chair.—A. Ogg: The electrostatic deflection in a cathode-ray tube. In the ordinary Thomson cathode-ray tube for determining the value of e/m for cathode rays, the irregularity of the electrostatic field near the edges of the charged plates has to be allowed for. It is interesting to find the electrostatic deflection when the rays are projected parallel to the plates, but at some distance from them. Methods for making the calculation were given.—Prof. J. D. F. Gilchrist: Note on a disease in the snoek (Thyrsites atun). The snoek, one of the most important Cape fishes from an economic point of view, is well known to be found frequently in a “pap” or soft condition. This is attributed by the fishermen to the fact that it has not been properly killed on capture, the consequence being that it struggles about in the bottom of the boat, and, in doing so, bruises the flesh to such an extent as to produce the condition mentioned. This condition may occur a few hours after the fish has been caught, and may quickly become so marked that the whole of the muscles, especially of the back, appear quite soft and liquid. The process is believed to be totally distinct from decay by putrefaction or by softening of the flesh by exposure to the heat of the sun, which also frequently occurs. As it wras suspected that this condition might be brought about by the presence and rapid multiplication of some protozoal parasite in the muscles, the diseased tissue was examined microscopically, and after staining with methylene-blue and other reagents the presence of very numerous spore-like bodies was detected. These were all arranged in groups of four, and occasionally, on fixation by heat, long filaments were shot out from them, showing that they were Protozoa belonging to the group of Cnidosporidia, which are known to produce diseased conditions in the muscular and other tissue of fish. The groups of four bodies with filaments suggest the family of the Chloromyxidas with their four polar capsules, but there is reason for believing that they represent spores, not polar capsules, and, if so, they probably belong to a new form of the Microsporidia.—Ethel M. Doidge: Mycological notes. I.