l 97 
In the fresh blood film, when it is drawn, numerous crescents are 
seen, but within five to ten minutes half the number of crescents have 
become vesicular and their pigment dancing; several have thrown out 
flagella, which are still attached after fifteen to twenty minutes. 
These vesicular gametes have become phagocyted by polymorpho¬ 
nuclear leucocytes; some of them at this period have parted with 
their flagella, because several free flagella were detected in the film. 
Stained preparations fixed immediately upon drawing the blood show 
nothing but crescentic forms, but films that have been kept moist from 
five to ten minutes before staining show that a very marked change 
has taken place in the crescents, many of them becoming either 
globular or irregular and distorted. One film fixed after ten minutes, 
and stained, showed nine crescentic forms, eight globular forms, witn 
discrete pigment and several chromatin dots, some of which are 
certainly microgametes, and eleven irregular forms, as though 
becoming globular, or as crescents losing their stiff outline, and 
becoming flexible. 
After fertilisation the microgametocyte becomes elongated 
(wandering vermicide, ookinet). Illustrations of wandering 
vermicules (after Grassi) are very much like the eleven irregular 
forms seen in the blood just described. I hese, then, may represent 
fertilised gametes. 
The fertilised gamete, or ookinet, if it be not phagocyted, has 
abundant time to wander out of the blood clot and reach the gut 
wall, for the blood-meal of the mosquito is usually not expelled 
until after twenty-four hours. 
The earliest form of the malignant tertian zygote was detected 
in the wall of the gut after the expulsion of the blood-meal, or after 
two and a half days. Satisfactory dissections and examinations 
cannot be made until the blood-meal has been expelled; 
consequently, after several trials, sixty hours after a feeding was 
the earliest period at which a search was made for zygotes. 
In Experiment No. 204, a specimen of Ce. (?) tarsimaculata was 
killed sixty-five hours after a single feeding from a patient w 
blood contained ten crescents per 100 leueqeytes. Lpon examina 
there were about fifty zygotes in the mid-gut. They were s igi y 
oval in outline, with closely clumped quiescent pigment, an very 
little cytoplasm showing beyond the pigment, the diameter being 
