378 
C. GnEDON HEWITT. 
contains a troplionucleus and kiuetonucleus. Division takes 
place by simple longitudinal division or multiple segmenta- 
tion, and in this manner a large number of individuals are 
formed (II h and III). These develop into the flagellate stage : 
a vacuole, the flagellar vacuole (III, /.r.) appears between the 
kinetonucleus and the I’ounded end of the pre-flagellate form, 
and in it the flagellum appears as a single coiled thread, which 
is extended when the vacuole has approached the surface. 
The flagellate form has already been described, and in the 
concluding portion of the flagellate stage, which, according 
to Prowazek, is found in starved flies, these forms are found 
collecting in the rectal region, and attaching themselves by 
their flagellar ends in rows to gut epithelium. The more 
external ones begin to shorten, during which process the 
flagella degenerate (IX) and are shed. Thus a palisade of 
pai-asites is formed, the outer ones being rounded and devoid 
of flagella, and some of them may be found dividing (X). 
Leger (1902) terms these the “formes gregariennes,” and 
maintains that the existence of these “gregarine” forms is a 
powerful argument in favour of the flagellate origin of the 
Sporozoa, which he had previously suggested, and which 
Butsclili had put foi-ward in 1884. After the degeneration of 
the flagellum a thickened gelatinous covering is formed, con- 
taining a double row of granular bodies (Xu), and these cysts 
are i-egarded by Patten as the post-flagellate stage. They 
pass out with the faeces, and dropping on the moist window- 
pane or on food, are taken up by the proboscides of other flies. 
Prowazek describes dimorphic forms of the flagellate stage, 
which he regards as sexually differentiated forms, but Patton, 
in a letter to me, says that he is unable to And any of these 
complicated sexual stages. According to Prowazek, one of 
these forms is slightly larger than the other, and has a greater 
affinity for stain. The dimorphic forms conjugate; their cell 
substance and nuclei fuse, and a resting-stage cyst is formed, 
but the subsequent stages have not been followed. He 
further states that the sexually differentiated forms may force 
