FURTHER NOTES ON A TRYPANOSOME, 
131 
for chromatin, and a green reaction for cytoplasmic and 
achromatic structures. The drawbacks to this stain are the 
uncertainty of action which seems to attach to all delicate 
double stains, and the fact that there is another loophole for 
uncertainty in the process of washing* out the stain; so that 
it remains doubtful in some cases whether the nuclear colour 
is absent from a structure, owing to the absence of chromatin 
or through the staiu having been washed out. 
Fuchsin gave quite good nuclear pictures, but did not 
bring up the flagellar apparatus sufficiently well. 
The drawings in the plate are made from two well infected 
leeches found infected in nature. They were at the early 
part of what I have called the middle period of digestion. 
For convenience sake the periods of infection may be 
divided into three, corresponding to the stage of digestion: 
(1) The early stage, when the blood is just coagulating, 
and when the first signs of the dai*k greeu-browu fluid is 
visible in the upper part of the intestine. The parasite at 
this time is in the condition of throwing ofi^ the original 
flagellum and adopting the resting state, during which 
division begins to take place. The parasites are for the 
most part still in the crop. 
(2) Middle period of digestion, when the intestine is full of 
the green-brown fluid, where breaking down of the blood is 
going on actively. The parasite is now in the intestine in 
large numbers. It shows the whole range of forms, from the 
spherical non-motile creature to the typical Trypanosome, 
(xreat variation in size and thickness of the pai’asites is to be 
observed. Very slender, long forms are only occasionally to 
be seen. This middle period is of very long duration, 
(3) Final period of digestion, when the crop is empty (or 
almost so) of blood, and the intestine nearly, or completely, 
free from the characteristic green-brown fluid. The Try- 
panosomes are now long, slender forms, with the kineto- 
iiucleus in the typical Trypanosome position. The forms now 
begin to remount the crop, and are also to be found in a still 
more slender condition in the proboscis. 
