Some Observations on a Flagellate of the Genus Cercomonas

Abstract

ABSTRACT In the present paper I shall describe a flagellate of the genus Cercomonas, a genus first created by Dujardin, in his Historie Naturelle des Zoophytes Infusoires,’ published in 1841. Since Dujardin’s original description numerous flagellates have incorrectly been attributed to this genus, so much so that Klebs, in his ‘Flagellatenstndien ‘(1893), says that this genus has not been defined with sufficient accuracy, that it has been confused with Heteromila and Bodo by the overlooking of the tail flagellum, and that the genus Cercomonas must be rejected. It is undoubtedly true that the genus Cercomonas is very confused, and this confusion has been considerably heightened by the description of Cercomonas from the intestine of man and other animals. Davaine (1854) was the first to record the presence of Cercomonas in the evacuations of a man suffering from cholera. Without going into the question of the correctness or otherwise of Davaine’s conclusions, it is undoubtedly a fact that many observers, noting the presence of active flagellates in the intestinal contents, have attributed them at once to the genus Cerco-inonas, and as a result of this various species of Trichomonas, Lamblia, and possibly other flagellates have been included in this genus. In the present instance the flagellate to be described was found in the fæces of a patient in the Albert Dock Hospital at the London School of Tropical Medicine. This patient was infected with Entamœba coli, andin order to observe changes in the encysted forms of this amœba some of the fæces were placed in a clean glass-stoppered bottle. In the course of a few days it was noticed that large numbers of flagellates were present. It is probable they had developed from cysts which must have been present in the fæces. On first examination it was seen that these flagellates corresponded very closely with the original description of Dujardin for the genus Cercomonas, and for this 1 took them to be. On more careful examination I found that the tapering posterior end was in reality a second flagellum, and that this could be traced along the surface of the body to which it was attached as far as the insertion of the long anterior flagellum. The presence of this posterior flagellum and its attachment to the body required very careful observation to make out, for it can only be clearly seen in certain portions of the animal, and it is quite conceivable, as Klebs maintains, that Dujardin overlooked this posterior flagellum. Dujardin’s original description of the genus is as follows :