
I shall first reproduce the description 
of ‘its characteristics from my previous pu- 
blications; after that 1 shall describe the struc- 
ture of the species and try to show in what 
it ressembles and how it differs from the 
type species of the genus Tetrachilomastix. 
One form of Ch. cayiae is elongate, 
from 12--17 micra long and about 4 
wide; the body is longitudinally depressed ; 
one of the margins is thicker and more 
convex than the other; the cytostome is 
oblique, or almost paralell with the body 
axis and ends at the limit of the less thick 
rim and the anterior extremity. 
In another form, the body is short, 
from 8—10 u Jong and from 4-5 wide. 
The extremities are equally rounded and 
very broad; the body is very much hollowed 
out longitudinaly; one of the margins is 
very thick, rounded and very convex, the 
other very narrow, almost blade-like and 
only slightly convex; the cytostome is per- 
pendicular to the longitudinal axis and ends 
at the most anterior part of the narrow 
margin, The limit between the blade-like part 
and the thicker one forms a neat curve, con- 
cave towards the narrow side, and at times 
in apparent continuity with the cytostomatic 
margin on the concave side of the curve; 
the flagella often lie hidden in the shape 
of a bundle. 
Both forms show endo and ectoplasm; 
the later is a rigid, more translucid, periplas- 
tic layer without any special morphologic 
characteristics; it prevents all movements and 
consequent variations of outline. The endo- 
plasm of some forms is slightly alveolar; in 
others it is quite hyaline aud in perfect con- 
tinuity with the periplast. It always contains 
either round or rod-shaped, bent, siderophi- 
lous granulations, which are not inclusions 
but form part of the cell. No other proto- 
monadina known to me has a structure like 
- that of Chilomitus; there is some ressem- 
blance between it and Selenomonas, which 
as yet has no definite place in the nomen- 
clature ; but Selenomonas has a membrane- 
like cellular outline. 
50 


The cytostome is almost always sac- 
like, sometimes narrowed at the orifice; it is 
from 3 to 4 w long, and at its widest about 
2 u across. 
No inner details were visible either in 
fresh orin stained specimens, nor were there 
any movements denoting the presence of an 
undulating membrane perceived. 1 saw no- 
thing that might be considered a chromo- 
philous lip like that of Tetrachilomastix ; the 
formation shown in one of our illustrations, 
which CHALMERS & PEKKOLA take for 
it, is only one of the many above-mentioned 
granules found in the plasm. 
The nucleus may also be of great use 
in distinguishing Chilomitus from other ge- 
nera, specially from Tetrachilomastix and 
Chilomastix. 
The latter always has a vesicular, sphe- 
ric nucleus, which is characterised by a 
thick, chromophilous nucleaer membrane; 
inside this, there is a clear zone which may, 
or may not, contain a caryosome and other 
chromatin and linin bodies. There is nothing 
of the kind in Chilomitus, which shows a com- | 
pact chromatic mass, that is sometimes visibly 
formed of roughly associated granules insi- 
de a clear zone. To conciliate this strange 
appearance with what is known about the 
cytology of flagellates, we may hazard the 
opinion that the clearzone is liquid, and the 
compact mass a caryosome; consequently 
the nucleus is of the protocaryon type, as I 
state in earlier publications. A sometimes 
very visible rhizoplast starts from the nucleus: 
and connects it which the blepharoplast. 
This is often large, not near the anterior end, 
but at the level of the inner side of the cy- 
tostome, so that the flagella seem to emerge 
from the latter instead of starting from the. 
former. 
There are four, anterior, equal flagella; 
in the short forms, in quiescent state, they 
are sometimes united in a bundle, which 
doubles under the body, sheltering tts free: 
end in the hollow formed by the cell-margin. 
From the above, careful study of the: 
internal structure and the external morpho- 
