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Trypanosoma lewisi 
chromatic and achromatic substance (Figs. 1, 3, and 5); the basal 
granule of the flagellum is sometimes well seen (Fig. 1). 
Trypanosomes taken from the flea’s gut, immediately after feeding, 
and kept in the incubator at 28° C. between the slide and cover-slip, 
showed also this transformation into crithidiae (Diagram III, Fig. 1), 
Fig. 1. Crithidia. O. 
Fig. 2. Chromidia arranged in a filament near the nucleus; blepharoplast absent. G. 
Figs. 3 and 4. Chromidia arranged in a twisted filament; nucleus and blepharoplast 
absent. G. 
Fig. 5. Two nuclei are present; the blepharoplast situated between them. G. 
but besides many degenerative changes occur which are not observable 
in the forms taken directly from the gut. The nucleus was often 
divided, a change which was never observed in the normal forms after 
24 hours. The blepharoplast was situated between the two nuclei 
(Fig. 5). Often the nucleus was completely degenerated and changed 
into a filament of chromidia (Figs. 2, 3, and 4), the blepharoplast having 
quite disappeared. These forms are very much alike to the “ male ” 
forms described by Prowazek and Baldrey in the louse, and to some of 
the forms found in the refrigerator by one of us (N. H. S.). The end of 
the degeneration was the complete disappearance of the protoplasm, 
only the flagellum remaining. 
In the living preparations the normal forms of 24 hours, as well as 
the forms preserved in the incubator, show another change in the 
general size, the hind-end being more or less thickened, so that the 
whole cell has the shape of a club. 
Second day. The number of the crithidiae is larger at this time, 
but otherwise the same forms may be found as during the previous 
stage (Diagram IV). Development still occurs in the midgut, although 
sometimes active flagellates may be found in the pyloric region. 
