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Trypanosoma lewisi 
when flagellates were to be found in the freshly dissected unstained 
gut, whereas in Series G no flea was considered to be free from 
flagellates unless the observation in vivo was confirmed by the study 
of stained preparations. 
This latter precaution is necessary because there were always very 
few flagellates to be found in the fleas of Series G so that they might 
easily have been overlooked during the observation of the fresh gut. 
The infection of the two fleas of Series G was only seen in stained 
preparations. 
We will now proceed to describe the various forms found on each 
day in the fleas of Series F. 
Twelve hours after feeding. During the first hours of their stay in 
the midgut of the flea the trypanosomes undergo many changes which 
affect the structure of the nucleus and blepharoplast, which have 
nothing to do with the subsequent development, and resemble the 
changes undergone by trypanosomes preserved for 7—11 days in 
the refrigerator (hypertrophy of the blepharoplast combined with the 
formation of chromidia, asymmetric segmentation of the nucleus, etc.). 
One of us (N. H. S. in a paper about to be published in Parasitology ) 
will deal with the different forms of degeneration exhibited by 
T. lewisi and will show how many of the figures interpreted by 
Diagram I. 
Fig. 1. Ordinary trypanosome. G. (dry fixation, Giemsa stain). 
Fig. 2. The same as Fig. 1. I. H. (wet fixation, Heidenhain stain). 
Fig. 3. Small trypanosome. Nucleus throwing out chromidia. G. 
Fig. 4. Trypanosome with blepharoplast throwing out chromidia. G. 
Fig. 5. Trypanosome with fragmented blepharoplast (resembling mitotic division of the 
blepharoplast, described by Prowazek). G. 
Fig. 6. Asymmetric nuclear division. G. 
Fig. 7. Hypertrophied blepharoplast throwing out chromidia. G. 
