A note upon the systematic position of “Trichomonas” keilini (Bishop, 1935)

In 1935 I described a free-living flagellate, which bore a striking resemblance to the genus Trichomonas , and was obtained, on four different occasions during a period of 12 months, from a pond in Lincolnshire. This flagellate has three anterior flagella, and a short marginal flagellum bordering an undulating membrane but without a freely-projecting end. There is no basal fibre at the base of the short membrane. The three free flagella and the marginal flagellum arise from a blepharoplast which lies in front of the single, anteriorly placed nucleus. There is a cystostome. An axostyle frequently is absent, but when present it is slender and siderophilic. Division is similar to that of Trichomonas hominis and T. batrachorum (Bishop, 1931).