A. C. Coles 
29 
the large fusiform trypanosomes, but only in very small numbers, in 
a very young thrush, July 28, 1912. Here they were associated with 
an enormous number of Leucocytozoa, and a few Halteridia. 
These hardly differed in their general appearance and structure 
from the large fusiform trypanosomes which stain a deep blue colour, 
found in the blackbird. (Plate II, fig. 4.) 
I have added a table of measurements of these trypanosomes. In 
the case of the trypanosome of the blackbird 40 parasites were drawn 
with a Zeiss camera lucida at an exact magnification of 2000 diameters, 
and in the case of the small trypanosome of the thrush 20 were drawn 
at 2000, and 20 at a magnification of 4000 diameters. 
The post-nuclear region was measured from the tip of the posterior 
end to the centre of the centrosome, the internuclear region from the 
last named spot to the middle of the nucleus, and the pre-nuclear from 
the centre of the nucleus to the extreme anterior end. From the 
measurements given it would appear as if the large trypanosome of the 
thrush was considerably longer than that of the blackbird, but as 
a matter of fact the measurement of the latter was made upon a very 
large number of parasites, many of which showed blunt round posterior 
ends, whilst comparatively few measurements could be made of the 
large thrush trypanosomes as these were so infrequent. In other words 
the disparity in length depends somewhat on the variable length of 
the region from the centrosome to the posterior extremity, yet the large 
Measurements of the trypanosomes found in blackbirds and thrushes. 
Total 
length 
Pre- 
nuclear 
Inter¬ 
nuclear 
Post- 
nuclear 
Greatest 
width 
Free 
flagellum 
Blackbird. 
1 
r Average 
39-75 IX 
18-0 
11-6 
5-3 
7-2 
4-6 
A. Fusiform J 
, Maximum 
48-0 
22-0 
12-5 
6-5 
8-0 
7-0 
1 
iMinimum 
33-0 
16-0 
10-0 
2-5 
7-0 
4-5 
1 
f Average 
26-8 
8-25 
8-8 
2-8 
8-8 
6-9 
Piriform J 
, Maximum 
30-0 
9-5 
9-5 
5-0 
8-5 
7-0 
1 
IMinimum 
22-5 
5-5 
7-5 
2-0 
9-5 
4-5 
Thrush, 
Small 1 
f Average 
28-92 
8-65 
8-27 
1-9 
5-6 
10-0 
trypanosome 1 
1 Maximum 
31-5 
10-0 
8-0 
2-0 
5-0 
11-5 
iMinimum 
23-5 
5-5 
7-0 
1-0 
8-0 
10-0 
Larger tryp. Average of two 
32-75 
11-0 
10-5 
2-5 
9-25 
8-75 
Large ^ 
( Average 
52-0 
24-5 
9-75 
10-25 
7-75 
7-5 
I Maximum 
59-0 
28-0 
9-0 
12-0 
6-0 
10-0 
trypanosome 
IMinimum 
46-0 
24-0 
9-5 
4-5 
9-0 
8-0 
