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315 
total length of both these varies from 30 to 35 p. The width of the 
narrow forms is from a half to a third of that of the wide forms. Both 
are characterised by having the non-flagellar end much drawn out 
beyond the micronucleus or nucleus as the case may be. It may be so 
marked as to give the appearance of a whip-like process or flagellum. 
The micronucleus is usually rod-shaped and prominent and is very 
uniform as regards its position in the body of the parasite. With 
reference to the nucleus its position varies but this is produced by the 
change in position of the nucleus rather than by any alteration in the 
situation of the micronucleus. 
The flagellum arises from a point near the micronucleus and is never 
directly connected with this latter structure. It pursues a slightly wavy 
course along the border of the undulating membrane to the extremity of 
the body whence it is prolonged as a free flagellum for a distance of 5'5 
to 7 p. The flagellum is a delicate structure which does not stain very 
deeply and is developed to about the same extent as in Trypanosoma 
lewisi. 
The nucleus consists of a roughly spherical group of fine chromatin 
granules and varies considerably in its position in the body of the parasite. 
It may be at the middle of the body (Fig. 4), or close to the micronucleus 
which, as pointed out above, varies very little in position. When in the 
latter situation, the nucleus may be on the flagellar side of the micro¬ 
nucleus as is usual in trypanosomes (Figs. 1 and 3), or it may be on the 
non-flagellar side (Fig. 5), as in the genus Herpetomonas. The occur¬ 
rence of both forms in the blood of any animal is not common. Herpe¬ 
tomonas forms have been noted in the case of Trypanosoma lewisi and in 
Trypanosoma theileri. More recently such a condition has been described 
in Trypanosoma wrublewskii. In invertebrate hosts it is more common 
and Minchin has recently shown that a herpetomonas form occurs in the 
life cycle of the trypanosome of Glossina palpalis. 
The flagellar extremity of the trypanosome is blunter than the very 
pointed non-flagellar end. 
The protoplasm of the parasite stains blue and is free from granules. 
It shows a marked alveolar structure, while in the narrow forms it is as 
a rule darker than in the wider forms. Such a condition might lead 
one to suspect that the wide forms are merely flattened out narrow 
trypanosomes. From an examination of a large number of trypanosomes 
it is clear that this explanation is improbable. To some observers the 
wide and narrow forms would appear as female and male respectively 
but nothing is known of the history of this trypanosome and nothing in 
