353 



Observations on the Life-Cycle of a New Flagellate, Helkesimastix* 

 faecicola, n.g,, n.sp. : Together with Remarks on the Question 

 of Syngamy in the Trypanosomes. 



By H. M. Woodcock, D.Sc, Assistant to the Professor of Protozoology, 

 University of London, and G-. Lapage, M.Sc, Assistant Lecturer and 

 Demonstrator in Zoology, Victoria University, Manchester. 



(Communicated by Prof. S. J. Hickson, F.E.S. Received July 3], 1913.) 



[Plates 13 axd 14.] 



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 con- 

 tinuous 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 3-3i fi 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 Amceba cysts. Some- 

 times bacteria are adherent to the cyst-wall (fig. 3). The protoplasm is 



* The generic name is formed on the analogy of the Homeric epithet, i\Ke<rnren\os, 

 trailing mantle or cloak. We are indebted to Prof. Minchin for suggesting this appro- 

 priate name. 



VOL. LXXXV1II. — B. 2 E 



