382 Trypanosoma lewisi 
The blepharoplast then passes the nucleus (which has been wandering 
to the posterior cell-end in the meantime) and so the crithidiae-type is 
produced. The crithidiae are thick or slender (Figs. 7 and 9) according 
to the flagellate having become club-shaped or not. During the first 
days, forms as drawn in Fig. 1 may be observed; they are due to 
agglomeration but might be taken for conjugation. 
These changes are observable during the first two days. The forms 
now to be described in lice could not be found in a regular series, but 
using as a guide the knowledge we acquired in the course of the 
investigation of the flagellates in fleas, we have arranged our results 
accordingly. 
All of these forms are found in the pyloric region of the hindgut. 
First of all the crithidiae and their flagella are shortened up (Diagram 
XVI, Fig. 1), the flagellates become broader (Figs. 4, 5) and at last 
rounded up (Figs. 6—8). 
Diagram XVI. 
Figs. 1—5. Transformation of crithidiae into large ovals. G. 
Fig. 6. Large ovals becoming rounded up. G. 
Figs. 7—8. Round forms. G. 
The minute cytological structures of all these forms are the same as 
those described in the flagellates of the flea. A well-marked karyosome 
is generally, though not always, to be seen; the blepharoplast shows 
generally its chromatic and achromatic components quite distinctly. 
Fig. 6 shows the division of the latter, the two daughter blepharoplasts 
being united by an achromatic centrodesmose. This figure shows also 
that the two chromatic granules present in many blepharoplasts do not 
indicate the beginning of division because the two daughter blepharo¬ 
plasts show already the double granule. The blepharoplast in Fig. 8 is 
also dividing. The flagella of the round forms do not stain well, 
generally they are not to be seen at all. The dividing nucleus of 
Fig. 6 seems to indicate that the division takes place in the same 
way as in the flea flagellates. 
The short crithidiae with short flagellum are identical with the large 
oval forms of the flea’s gut; they resemble Rodenwaldt’s “ ookinetes.” 
