374 
Trypanosoma lewisi 
the flagellum becomes achromatic under certain conditions, but that it 
is always present as an intercellular flagellum. 
All the different types to be described here may show signs of 
division, but the multiplication in this last stage of development results 
mainly from the division of round and small oval forms. 
The small oval forms become larger (Diagram X, Figs. 5—7, 
Diagram XI, Fig. 8) and may divide again (Diagram X, Fig. 8, 
Diagram XI, Fig. 9). When doing this they may be rounded up 
again, forming small round forms (Diagram X, Fig. 4). At last they 
are transformed into well-marked Crithidiae, the flagellum growing 
out (Diagram X, Figs. 9—12, Diagram XI, Figs. 10—12). A slender 
and a thick type (Diagram X, Fig. 13 and Diagram XI, Fig. 12) 
may be distinguished united by intermediate forms (Diagram X, Figs. 
11, 12, Diagram XI, Fig. 10). These Crithidiae may divide also 
(Diagram XI, Fig. 11). One might think these forms to be sexually 
differentiated, but when looking at the variation in size of the Crithidiae 
found in cultures (cf. Diagram XII, Figs. 1—3) this dimorphism seems 
to be of no essential significance. 
The slender Crithidiae undergo further changes (Diagram XI). 
The flagellum becomes longer and the undulating membrane more 
developed. At the same time the protoplasm, which stained dark 
blue, takes a paler blue colour. The development of the undulating 
membrane is due to the fact that the blepharoplast leaves its position 
anterior to the nucleus (Figs. 13, 14), comes first beside the nucleus 
(Figs. 16—17) and finally takes a position at the extreme posterior end 
of the cell (Fig. 18). The flagellate has now recovered the aspect of a 
perfect though small trypanosome, which is however very different from 
T. lewisi found in the blood not only in size but also in structure. 
The protoplasm is stained pale blue with Giemsa. The blepharo¬ 
plast, with its characteristic position already mentioned, is generally 
very large after Giemsa staining; in the Heidenhain preparations it is 
much smaller because in this case only the chromatic part is stained 
(Diagram X, Fig. 15). The basal granule is generally very distinct 
(Diagram XI, Fig. 19). The nucleus is sometimes round (especially 
previous to division) but it is often much elongated. Sometimes a 
karyosome is well marked, but often there are several chromatic 
granules to be found in the nucleus, not only in Giemsa preparations 
but also in those stained after Heidenhain (Diagram X, Fig. 15, 
Diagram XI, Figs. 18 and 19). The undulating membrane is not 
broad and consequently not much curved. When the flagellate is 
