455 
the periods of the greatest number of parasites in the blood, is fully 
twice as thick as the flagellum. As it increases in length it may 
reach, or even pass the nucleus ; or it may become coiled upon itself, 
as in figs. 16, 17, 18. But whatever form it takes at first, the later 
appearance suggests that the band eventually becomes in one way or 
another definitely connected up with the nucleus. This suggestion is 
strengthened by the subsequent behaviour* of the band, for it is seen 
eventually to become gradually less stainable, to break up into a 
string of fragments, and finally to disappear. Through all these 
later stages of its existence it is most certainly suggested, as in 
figs. 19, 20, that it is directly related to the nucleus, that is to say, to 
have been, or to be actually connected up with it. 
We appear then, at or near the maximum number of the parasites 
in the blood, to have direct evidence of some sort of interaction 
taking place between the extra-nuclear centrosome and the nucleus. 
This phenomenon occurs only among animals in which no evidence of 
nuclear division, or cell division, is apparent. In such cases, we do 
not find that either the extra-nuclear centrosome or the nucleus is 
divided, and throughout the whole development of the stainable band 
the nucleus remains in a condition of complete repose. 
If now we examine the portions of the curve of infection where the 
trypanosomes are decreasing in number, still other phenomena make 
their appearance. The numbers of the parasites gradually decrease 
in the peripheral blood, and at this time, in such organs as the lungs, 
the spleen, and the bone marrow, we find curious changes to be taking 
place in vast numbers of the trypanosomes encountered in these 
situations. Parasites showing the present changes are rarely found 
tn the organs named above during the period when the number of the 
Parasites is increasing in the blood, but at the time when the numbers 
are beginning to decrease we see in the lungs that numbers of 
trypanosomes show alterations in their nuclei. T he protoplasm of 
the animal’s body becomes detached from the periphery of the nucleus 
" hich lies in a clear space, while the nucleus itself contracts somewhat, 
and at the same time a large clear vesicle gradually grows up in 
connection with it, in the manner represented in figs. 22, 23. Round 
the outside of this vesicle and the nucleus there may be seen a layer 
01 protoplasm enclosing in a delicate sheath both nucleus and vesicle 
together. When this stage has been reached, the rest of the cell body 
