264 
Herpetomonads 
being withdrawn into the cell. Patton (1909), also referring to 
H. muscae-domesticae, says the flagellum degenerates and is shed. 
Rosenbusch (1910) describes the withdrawal of the flagellum into the 
cysts of Crithidia muscae-domesticcie, Werner. In the Hagellates from 
Neuroctena and Homalomyia the kineto-nucleus travels back, taking 
the end of the flagellum with it, till it comes to lie alongside or even 
behind the tropho-nucleus. In this way the greater part of the flagellum 
is actually drawn into the interior of the cell, where it is afterwards 
absorbed (see figs. 33 to 37). The position of the kineto-nucleus at 
these stages produces a crithidia- or even a trypanosome-like appearance, 
but there is, of course, no hint of an undulating membrane 1 . Frequently 
the connection between the kineto-nucleus and the end of the flagellum 
is lost, and the kineto-nucleus wanders into a different part of the cell. 
On one occasion only did I see a glutinous cyst-wall formed, such as 
has been described by Prowazek and others (fig. 38). It appeared as a 
faint pink cloud round a large circular cyst, in the centre of which was 
the tropho-nucleus, surrounded by a number of small, deeply-staining 
granules. 
The final stages of encystment were not often met with. They are 
small, oval or circular bodies (3/a x 3'5/a—4/a x 2'5/a), the cytoplasm 
staining a deep blue with Giemsa, and containing a dark-red tropho- 
nucleus and a kineto-nucleus: a reddish cyst membrane could sometimes 
be made out. Fig. 416 shows such a cyst stained with iron-haema- 
toxylin. 
Conjugation. 
Curious flagellates were occasionally found in Giemsa preparations 
both from the larva and from the fly, where the tropho-nucleus had 
disappeared, leaving the cytoplasm staining rose-pink (figs. 29—31). 
Otherwise these forms seemed to be quite normal, though some of them 
were very small (fig. 30). I was interested to notice in one case (fig. 29) 
that division could apparently take place in the virtual absence of the 
tropho-nucleus. The kineto-nucleus was dividing, as was also the base 
of the flagellum ; two minute, faintly-staining dots alone indicating the 
normal position of the divided tropho-nucleus. 
Such individuals would be regarded by certain authors as male 
gametes. I have watched the living organisms for hours at a time, and 
have never seen any sign of conjugation. For my part, I consider these 
1 One cannot help being struck by the resemblance of some of these stages to the 
flagellate of Crithidia muscae-domesticae as figured by Werner. 
