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Herpetomonas lueillae n. sp. 
This species is therefore probably distinct from H. muscae domes- 
ticae at least, and I therefore propose for it the name Herpetomonas 
luciliae. 
It has been said that such parasites as these are ‘ biflagellate,’ 
because certain forms appear to have two flagella. The appearance, 
however, is deceptive, and these parasites in reality only have one 
flagellum in which the two chromatin filaments stain very prominently. 
The term ‘ biflagellate ’ is only applicable to those forms, rare in 
H. luciliae, in which there are two free flagella. 
Prowazek, Chatton, and others would use this inconstant form of 
the parasite—the so-called biflagellate form—with which to define the 
genus Herpetomonas, and would separate it from Leptomonas, which has 
a slightly different type of flagellar apparatus. 
Miss Mackinnon, however, has shown that a ‘ Leptomonas ’ in the 
larval host may become a ‘ Hei'petomonas ’ in the imaginal host, and 
that the difference in the flagellar apparatus is only a matter of the 
time at which the flagellum divides. It seems therefore wrong to class 
these parasites into two genera. 
They would thus all be named Herpetomonas, sensu Pattoni, who 
defines them as having no undulating membrane and the blepharoplast 
near the anterior end of the cell. 
The method of infection of the fly. 
The experiments performed in order to discover how the parasite is 
transmitted from fly to fly were conducted in the following manner. 
An attempt was made to raise ‘ clean ’ flies in the laboratory, but 
owing to the cold summer (1909), and also because the experiment was 
begun rather late in the year, the pupae obtained did not hatch out. 
Recourse was therefore had to flies caught wild, and in estimating the 
results obtained with these it was borne in mind that 76 “/o of them had 
been previously found infected. 
The flies were kept in a large fly net, but they were with difficulty 
kept alive. They were fed on fresh meat contaminated with the 
rectal parasites of other flies, and afterwards were killed at definite 
intervals and examined for parasites. 
The result was meagre, but three flies which had been fed as 
described above showed actively growing cysts in the ‘ crop ’ two days 
later; whereas of flies examined straight from nature, I never found 
one containing these forms in the ‘crop.’ 
