Abstract
(1) The microfilariae of L. loa, W. bancrofti, B. malayi, D. immitis, D. repens and D. aethiops have been studied in detail, using phasecontrast and ultra-violet microscopy and vital staining techniques.(2) In these microfilariae the cells of the “oten Mundgebilde” have been renamed “hook-muscle cells” as they appear to be concerned with the movements of the hook.(3) Two cells have been demonstrated in the nerve ring by means of ultra-violet photomicrography and vital staining with rongalit methylene blue.