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end is the more rapid in growth, the endoplasm flowing forwards and 
pushing the ectoplasm before it. The contents of the chromatophile 
area concentrate and gradually differentiate into a thread (fig. 4), 
which gains the surface and forces the ectoplasm outwards forming 
the wavy membrane. The final portion of the thread protrudes beyond 
the body as the free flagellum (figs. 6-8). The posterior end of the 
flagellate develops less rapidly than the anterior end. Division may 
occur while the pre-flagellate stage is merging into that of the flagel¬ 
late, and repeated division produces rosettes (figs. 3, 5, 8). All the 
pre-flagellates do not develop at the same rate, consequently some of 
the members of a rosette are still oval while others have already 
developed their flagella and membranes to some extent (fig. 8). 
The somewhat frail appearance of the pre-flagellates is certainly in 
contrast with the relatively gross facies of the mature flagellate, but 
the whole development has been watched repeatedly in life and is 
unmistakable. 
The Flagellate Stage. 
The flagellate form of G. pulicis (figs. 9—17) is an organism 
measuring from 26 g to 65 g long, the free flagellum being included. 
The body is elongate and the flagellar end prolonged and finely tapering. 
The aflagellar posterior end is relatively blunt, being somewhat rounded 
in the fully formed individual (figs. 16, 17). The general protoplasm 
is richly granular but the granules are fine. The nucleus is oval, rich 
in chromatin, the chromatin being in the form of refractile granules in 
life and staining well whatever stain be employed (figs. 10, 12, 17). 
Its position in the body varies somewhat. Frequently it is about a 
third of the way between the two ends of the organism (figs. 14, 
16, 17), but occasionally after periods of great activity of the parasite, 
it is found nearer the flagellar end. 
The blepharoplast is large, usually lying horizontally across the 
body of the organism (figs. 9, 11, 15), and as a rule extending almost 
across the transverse diameter. Commonly it presents a homogeneous 
structure except when in division. Its shape may be oval (figs. 10, 15- 
17), rod-like (figs. 11, 13), or curved slightly. All the forms have been 
seen in life and the stained specimens merely corroborate the obser¬ 
vations in vivo. In a few cases, a vertical blepharoplast has been 
found. This is uncommon but it has been recorded in many other 
Crithidia. There are a few chromidia (fig. 16) present in many of the 
16—2 
