INFUSORIA AS PARASITES. 
299 
Stein, in connexion with Trichomonas batrachorum, which inhabits, 
in common with many other infusorial types, the alimentary 
canals of frogs and toads, that what was previously reported 
to be a supplementary fringe of cilia is actually a delicate 
frill-like undulating membrane, corresponding closely with 
that possessed by Trypanosoma Eberthi, and assisting, in 
conjunction with the three or four flagella, in the locomotive 
function. An illustration of this species, as recently delineated 
by Stein, is reproduced in PI. VII. fig. 17. Two other species 
of the same genus, Trichomonas vaginalis and T. limacis , are 
associated respectively with the human subject and the garden 
slug. A second endoparasitic Polymastigous form, in which the 
flagellate appendages are no less than six in number, four 
being inserted at the anterior and two at the posterior 
extremity of the body, is represented by the genus Hexamita , 
instituted, in common with Trichomonas , by Dujardin, and 
containing in like manner three or four well-differentiated 
species. The typical representative of this genus, Hexamita 
intestinalis (PI. VII. figs. 18-20), occurs abundantly in that 
prolific hunting-ground for parasitic organisms, the rectum 
and intestine of the frog, Rana temporaria , and has recently, in 
association with examples of this Batrachian dissected at the 
South Kensington Biological Laboratory, been the object of 
investigation by the present writer. As a result of this 
investigation, one or two points of interest concerning the 
deportment of these singular animalcules in the fluid medium 
they inhabit were placed on record. While usually described 
as essentially free-swimming organisms, it has been ascertained 
by the writer that they possess the faculty also of attaching 
themselves at will to associated objects, and of passing a 
temporarily sedentary existence. When first transferred to the 
field of the microscope, no such property is exhibited, the little 
creatures hurrying hither and thither in the most aimless and 
excited manner. Gradually, however, their movements grow 
more tranquil, till at length scarcely an animalcule is to be 
seen exhibiting its natatory capacities, all with rare excep- 
tions having attached themselves to the organic debris or other 
suitable fulcra, through the medium of their two trailing 
posterior flagella, which possess a marked adhesive function. 
Sometimes, the entire lengths of these filiform appendages are 
utilized as organs of adherence, and sometimes only their 
distal extremities. Under these last-named conditions, a 
highly remarkable modification of the movements of this 
animalcule has been observed. Where the adhesion is 
effected by the entire length of the flagella, the motion of 
the bod}?' is simply oscillatory, the four anterior flagella being 
deployed and agitated without apparently any definite plan of 
