Observations on the life-cycle of a new flagellate, Helkesimastix fæcicola , n. g., n. sp.: Together remarks on the question of syngamy in the trypanosomes

Abstract

This new flagellate occurs frequently in goat-dung; we have found it also in sheep-dung. It is a “passenger,” being carried passively through the alimentary tract, in an encysted condition. When the dung is moistened with water—probably, in nature, when it is deposited on damp grass or earth—the flagellate emerges from its cyst and goes through its life-cycle, ultimately encysting again. The cysts are doubtless swallowed by the goat with its fodder. We have cultivated Helkesimastix under various conditions, which will be described in our full account later. In order to obtain this form in large numbers and study its life-history without any fear of being misled by stages in the life-cycle of other flagellates, we succeeded in isolating it from the other forms occurring in simple dung-cultures and cultivating it on agar-media, on which it multiplies rapidly. The medium which we have used principally is weak Lemco-agar, i. e. the same medium as used for blood-agar, but considerably diluted. For our con­tinuous observations we have used hanging-drop preparations in sealed cells; in these cases we used very dilute Lemco-broth, without any agar, as the medium for the development of the flagellates, because in the denser agar-medium it is very difficult to see the flagellum. In all these media the flagellate forms the protozoan component of a “mixed culture,” since there is, of course, an even greater and more rapid bacterial development. Commencing the account of the life-cycle with the permanent cyst, this is a small spherical or slightly ovoid body about 3-31/2 μ in diameter (figs. 1-3). The cyst-wall is well defined, but not very thick; it appears to consist of a single membrane, there being no differentiation into inner and outer envelope such as is found, for example, in many Amœba cysts. Some­ times bacteria are adherent to the cyst-wall (fig. 3). The protoplasm is fairly homogeneous, or contains fine granules. There is frequently, however, a conspicuous, somewhat refringent grain, situated near the periphery (Plate 13, figs. 1 and 2), but no vacuole is present. The nucleus can usually be seen as a clearer, area, and at times the contained karyosome can be distinctly made out as a dull body in the centre. No division takes place inside the cyst, which is therefore a resting or “Dauer” cyst and not a multiplicative one.