N. H. SWELLENGREBEL AND C. STRICKLAND 
369 
Some of them are figured in Diagram VI, Fig. 2, a large oval form 
shows a double basal granule of the flagellum probably marking a 
subsequent division. 
Diagram VI. 
Fig. 1. Crithidia. G. Fig. 2. Large oval form. G. Fig. 3. Round form. G. 
Fifth day. The fleas dissected on this day showed only very few 
round forms in the rectum (Diagram VII) probably they were washed 
out of the hindgut. Some of these forms showed division. The 
flagellum was only to be seen as a bright line within the cell. 
Diagram VII. 
Fig. 1. Dividing round form. G. Fig. 2. Non-dividing round form. G. 
Sixth day. The same stages were to be seen as on the fourth day 
(Diagram VIII). The diagram shows two rosettes, one stained with 
Giemsa, the other with Heidenhain ; Fig. 2 shows a large oval form 
(a) a slender crithidia, ( b ) thick crithidiae, (c) and a dividing round 
form, (d) in one rosette. The large oval form of this rosette has yet 
an external flagellum. Fig. 1 shows a rosette of large oval forms and 
a dividing round one. One of the large oval foi’ms is dividing but this 
is rather uncommon, because the large oval forms generally become 
rounded up before the division begins. We do not exactly know how 
these rosettes of large oval and round forms originate; we do not think 
