NEW TYPE OF PEOTISTAN PAPASITE. 
455 
Pro - Flagellate, Selenomastix ruminantium (Certes) 
represents such a Protist, because of the fact that it exhibits 
certain characters which are common to the flagellate Pro- 
tozoa, but which are rarely or never possessed by bacteria. 
The Lister Institute, 
July, 1913. 
Summary. 
(1) This paper describes a new type of parasitic Protist, 
to which we have given the name Selenomastix rumi- 
nantium (Certes). Its habitat is the rumen of Ruminants, 
especially that of the goat. 
(2) The organism occurs in two chief forms — crescents and 
ovals. The crescents present a homogeneous, non-granular 
appearance, and possess a deflnite envelope ; a single, large 
flagellum, conspicuous in life, arises from about the middle of 
the concavity of the crescent. The method of movement is 
variable ; while the movement is sometimes effected by the 
flagellum, in other cases, perhaps more usually, it is produced 
by the body alone. In forward progression distinct antero- 
posterior polarity can be recognised. There is no properly 
constituted nucleus, the chromatin being present iu the form 
of a peripheral layer, in which granules of varying size may 
occur, or there may be one or two large masses projecting 
into the cytoplasm. Division is by equal binary fission, 
transverse to the long axis. 
(3) The ovals resemble the crescents in general, but they 
never possess a flagellum, although capable of active move- 
ment. They show two types of minute structure : (a) ovals 
in which the chromatinic substance occurs as a narrow, 
peripheral layer, with or without granules in it. This 
arrangement agrees closely with that found in the crescents. 
(b) Ovals in the protoplasm of which two zones can be 
distinguished , a central, lighter-staining zone, comparable to 
the cytoplasm of (a) and of the crescents, and a peripheral, 
darker area of variable extent. This latter may be chroma- 
tinic in nature. 
