14 PROF. E. A. MINCHIN ON PROTOZOAN [Jan. 12, 
stretched out, with the undulating membrane rippling actively, 
the undulations commencing at the flagellar extremity and pass- 
ing backwards down the body. They travel usually with the 
flagellum forwards and the body straightened out; the movement 
is effected apparently, chiefly by the undulating membrane; the 
blunter posterior prolongation of the body meanwhile performs 
curling or wagging movements which appear to be of a passive 
kind, the result of the movements of the undulating membrane. 
T saw a trypanosome, travelling in this manner on a slide under 
a coverslip, approach and go straight through a closely packed 
mass of blood-corpuscles, flagellum foremost and body straight. 
The same trypanosome was seen also to reverse its movement and 
move with flagellum directed backwards; the blunter extremity 
of the body, now foremost, performed movements which appeared 
to be active in nature, and to assist the body in penetrating 
forwards. ‘This was observed also in other cases. ‘Trypanosomes 
which were travelling actively were observed to come to a stand- 
still and perform simply wriggling movements ; conversely, 
trypanosomes which have been wriggling for some time may 
start off and begin travelling. 
The smaller forms were very similar to the large forms m 
their general appearance and the character of their movements, 
and only differed in their small size, pronounced slenderness, and 
much greater activity and rapidity of movement. 
The trypanosome of the perch does not seem to possess the 
extraordinary vitality of 7’. granulosum of the eel. 1 found that 
the trypanosomes did not live more than a few hours an vitro. I 
made an observation, however, relating to their vital powers 
which perhaps is not without interest. From a perch which was 
very well infected, and from which I made a number of smears 
(fig. 11 was taken from this fish) I took three drops of blood; 
one drop was simply placed on a clean slide and covered with a 
cover-glass; the second drop was placed on a slide and mixed 
with a drop of Laveran’s salt-citrate solution, and then covered ; 
the third drop was put on a slide and mixed with a drop of tap- 
water, and then covered. The three drops were studied from 
time to time. In the drop mixed with water the trypanosomes 
showed greatly increased activity after about an hour, travelling 
with great rapidity in the hemolyzed blood; after four hours 
they were still very active, but not quite so active as they had 
been earlier. After five hours I slipped off the coverslip, smeared 
out the blood, dried it, fixed it with absolute alcohol, and stained 
it with Giemsa’s stain. The trypanosomes stained well and 
appear perfectly normal. In the drop of blood mixed with salt- 
citrate solution the trypanosomes also remained active but some 
of them were changed in form after four hours, the body becoming 
pear-shaped, with most of its substance aggregated at the hinder 
end. In some cases the trypanosomes appeared as if anchored 
by the hinder end; the anterior end of the body lashed round in 
all directions, but seemed unable to move the inert posterior 
