STUDIES ON PArvASmC PROTOZOA. 
461 
in the extreme interest to protistologists of such erratic para- 
sitic forms. 
(a) Rhizomastix GtRacilis Alexei eff. 
The Flagellate Form. 
A full description of the adult flagellate has been given by 
Alexeieff (1911). 1 quote the essential points. The form of 
the body is generally elongated, but may become globular ; 
the posterior end is especially ‘Anetabolic.'” The single 
flagellum is about three times as long as the body; a small 
basal granule marks its emergence^; it is continued into the 
body by a sort of dark-staining filament, the r hi zo style, 
“ qui atteint presque la longeur du corps et qui diminue brus- 
quement de calibre en passant au voisinage du noyau, comme 
si une partie de la substance de la baquette s’arretait a la 
membrane nucleaire.^’ The nucleus is very large, with volu- 
minous karyosome, usually central ; the peripheral chromatin 
is in the form of granules, connected with the karyosome by 
linin strands. The cytoplasm shows the clear alveolar struc- 
ture characteristic of Cercomonas. 
Alexeieff gives no measurements. The measurements I took 
showed the dimensions of the elongate flagellate individuals 
to be from 6g xogtoll^xog. The diameter of the large 
round forms was about 6 /.t to 8 g. 
Figs. 1-7 (PI. 31) show the appearance of the flagellate 
Rhizomastix gracilis as 1 found it in Tipula. 
E n c y s t m e n t . 
The oval bodies, en bouteille, a goulot tres court,” which 
Alexeieff first described as the cysts of Rhizom astix (1911a), 
he referred later (1911b) to CTiilomastix caulleryi. 
^ This basal granule mentioned by Alexeieff appears rather as a 
thickening of the rhizostyle than as a granule ” ; sometimes it is 
possible to see a minute granule at the inner termination of the 
rhizostyle within the body of the organism, see figs. 2, 4 and 6. 
