STUDIES ON PARASITIC PROTOZOA. 
465 
Rliizomastix. The rhizosfcyle of Rhizomastix is very 
possibly homologous with the much-debated fibril Doppel- 
facleu/^ that Prowazek was the first to demonstrate in 
H e r p e t o m o n a s m u s c ae - d o m e s t i c as . 
My account of the encystment does not add much to help 
in determining the systematic position further. Cysts of 
Cercomonas have been described by Hartmann and Chagas 
(1910)^ Wenyon (1910), and Alexeieff (1911), but those seem 
in every case to be mere Schiitzcysten,’^ in which no division 
phenomena take place. Doflein (1910) and Ogawa (1913) 
have described and figured certain globular forms which 
occurred in their cultures of Trypanosoma rotatoriurn. 
I have been struck by the resemblance of these to the cysts 
of Rhizomastix. One of Doflein^s figures in pai-ticular 
shows a large vacuole filling out the bulk of the sphere, and 
crushing aside the cytoplasm, which contains two nuclei. 
There are kinetonuclei present, of course, and there is no 
cyst-wall ; in other respects the picture is not unlike what I 
have shown in PI. 32, fig. 26. Ogawa describes these as 
Ruhe oder Dauerformen.’^ 
It is very difficult to say how far a similar mode of nuclear 
division indicates affinity between protozoa. The division 
of Rhizomastix within the cyst does not bear much resem- 
blance to that of Cercomonas flagellates as described by 
Hartmann and Chagas and others. On the other hand, 
the division of Trypanosoma lewisi is a mesomitosis 
according to certain authors. 
If importance is to be attached to such points as these, then 
thestudy of Rhizomastix gracilis tends to strengthen the 
view that the T ry pan o so m id ge Doflein {= Herpetomon- 
adidas Alexeieff) are derived from Cercomonadine ancestors. 
(b) Tetrateichomastix Parish, n. sub-gen., n. sp. 
G-eneral Considerations. 
'rhough the trichomonad flagellates have received much 
attention from a number of workers during the last few years. 
