104 
F. Cavers. 
the Monadaceae in general structure—for instance, Chlorcimceba is 
sometimes colourless and in this condition can hardly be distin¬ 
guished from a Monas. 
The Bodonacese, or Heteromastigoda, are closely related to 
the Monadaceae, though they may have arisen directly from the 
Rhizomastigaceae, for Bodo (Fig. 2, P) hardly differs from Cercobodo 
except that it does not pass into an amoeboid phase—it ingests its 
food directly, in the amoeboid manner, which is characteristic of 
the Bodonacese, the only member of this family showing vacuolar 
ingestion being Pleuromonas (Fig. 2, Q); in both genera one of the 
flagella is frequently used to attach the organism to a firm substratum. 
In the remaining genera the body shows elaborations related to 
food ingestion ; in Phyllomitus (Fig. 2, R) there is a funnel-like oral 
groove, in Colponema (Fig. 2, S) this groove is continued laterally 
to the posterior end of the body, and in Rhynchomonas (Fig. 2, T) 
one flagellum is replaced by a curious motile stout process forming 
a prolongation of the anterior end of the oral depression. It may 
be noted that the genera Bicceca and Poteriodendron are placed in 
this family by Lauterborn (1899) who regards the stalk by which 
the body in these thecate genera is attached to the base of the cup 
as being a second, backwardly directed, flagellum—an ingenious 
and highly probable interpretation; also that part of the Haemo- 
flagellata (Trypanosomes) is regarded as having arisen from Bodo - 
like forms and as constituting a sub-family (Trypanosomatidae) of 
Bodonaceae, including the genera Trypanosoma, Trypanophis and 
Trypanoplasma. 
The families Trimastigaceae and Tetramitaceae, characterised 
respectively by having three and four flagella inserted at the anterior 
pole of the body, despite certain general resemblances, are probably 
not closely related but have arisen independently from the Panto- 
stomatinea?, though they appear to have developed along parallel 
lines. Among Trimastigaceae the body may be cylindrical with the 
flagella arising from the anterior pole ( Elvirea , Fig. 2, U); or spindle- 
shaped with one flagellum inserted at the anterior extremity and the 
other two at a constriction some distance behind this (Dallingeria, 
Fig. 2, V)—in these genera two flagella are directed backwards; or 
pyriform with a longitudinal wing-like projection. Similarly the 
Tetramitaceae are divided into cylindrical forms either without 
( Trichomastix , Fig. 2, W) or more often with an oral groove which 
may be either limited to the anterior end of the body ( Tetramitus , 
Fig. 2, X) or traverse its whole length ( Collodictyon , Fig. 2, Y); 
and forms with a wing-like outgrowth or undulating membrane 
( Trichomonas , Fig. 2, Z). 
(To be continued). 
