A909. BLOOD-PARASITES OF FRESHWATER FISHES. i 
-and especially in the smallest forms, the undulating membrane is 
very deep, and stands out far from the body, with fewer and 
larger pleats (figs. 8-12). It generally appears clear, but in some 
cases the granules of the cytoplasm can be seen extending up into 
it, forming a distinct contour-line close under, but quite separate 
from, the flagellum (fig. 12). 
_ In one of my preparations, which had been fixed first with 
osmie vapour and then with Schaudinn’s fluid, without drying, 
and stained with iron-hematoxylin, I found the trypanosomes 
showing distinctly striations which are doubtless to be explained 
as myoneme filaments (figs. 96, 97). They are to be made out 
on both surfaces of the body running spirally, and hence appear 
to cross in the drawing, but in the object they are seen at 
different foci on the two surfaces. In one trypanosome they 
appear to run in couples (fig. 96). In another, which was much 
bent up and probably contracted, the myonemes can be seen on 
one surface running to a very convex edge, where they appear in 
optical section as distinct grains, and from this point they can be 
traced again on the other surface (fig. 97). The exact number 
was difficult to make out; fig. 96 indicates that there are in all 8, 
or 4 couples, but in fig. 97 there appear to be more than this. 
To these myonemes may be referred the active wriggling move- 
ments of the trypanosomes. 
In some of my preparations stained with Giemsa’s stain I found 
very broad forms of the trypanosome. Jam convinced that these 
forms are simply stout forms of the trypanosome deformed and 
flattened out by drying. In slides fixed with osmic vapour before 
drying I find them only at the edge, or in very thin parts of the 
film, that is to say in places where it is difficult to avoid a sight 
amount of drying taking place. ‘Two other points are to be noted 
in favour of this conclusion; one is that the very broad forms 
are not so opaque as the stout forms which do not show any 
flattening; the other is that the nucleus is more or less consider- 
ably elongated in the transverse direction, having evidently shared 
in the increase of breadth produced by the flattening. 
In one preparation, fixed wet with osmic vapour and stained 
by Giemsa’s method, I found a trypanosome apparently encysted 
(fig. 15). No trace of a flagellum was to be seen, but the body is 
rounded off and surrounded by an envelope staining a faint 
bluish tinge. The shape of the nucleus indicates perhaps that a 
slight amount of flattening has taken place. No other similar 
stage was found. 
In preparations from a perch which showed abundant trypa- 
nosomes in its blood, I found, on two separate slides, two bodies 
resembling heemogregarines (fig. 16); they were free in the blood- 
plasma and strongly resembled the free vermicules of these para- 
sites. It is well known that hemogregarines occur commonly in 
marine fishes, but in freshwater fishes they have only been found 
in the eel. I searched long, but in vain, for intracorpuscular 
Proc. Zoon. Soc.—1909, No. IT. 2 
