PROGRESS IN PROTOZOOLOGY

PHYLOGENETIC RELATIONSHIPS AMONG PROTOZOA 189
the 1980 classification of Levine's Committee. Thus Histomonas and
Dientamoeba (see Honigberg and Bennett 1971, Honigberg
and Kuldova 1969, Honigberg in Camp et al. 1974) are considered
as modified trichomonad genera (order TRICHOMONADIDA);
Tetramitus and Naegleria have been included in the rhizopod order
SCHIZOPYRENIDA Singh, 1952.
According to V i c k e r m a n, in certain respects Mastigamoeba resembles
the cercomonads. It possesses the prenuclear cone of microtubules,
pseudopodia, and similar mitochondria, but it lacks the postnuclear
organelle and the extrusomes; furthermore, there is no recurrent
flagellum but only a barren kinetosome corresponding to the basal body
of this flagellum. Evidently, Mastigamoeba has structural resemblance
to the myxamebae of some EUMYCETOZOEA. In a personal communication
to me, Vickerman wrote: "Mastigamoeba bears such a close
superficial resemblance to slime-mold flagellates that I cultured one of
the latter believing it to be Mastigamoeba for several years (as cyst,
amoeba and flagellate) — till one day it produced beautiful plasmodia."
Vickerman wondered if, indeed, the affinities of mastigamoebae lie with
mycetozoan sarcodines rather than with any known flagellate group.
He stated, however, in the course of the discussion at the Warsaw Congress
that a post-nuclear organelle was found in Rhipidodendron and
Spongomonas, both sedentary colorless flagellates with homodynamic
flagella (H i b b e r d 1976). "Is it possible (he asked) that heterodynamism
of the two flagella has been lost as a result of adoption of the
sedentary habits?"
With regard to another genus, Mastigella, which used to be included
in RHIZOMASTIGIDA, Vickerman stated that two species of the
genus, Mastigella vitraea and Mastigella hylae, appear quite different
from the species of Mastigamoeba. Since nothing is known about the
fine structure of Mastigella vitraea, its assignment to any existing or to
a new taxon is not possible at this time. On the other hand, it is known
that Mastigella hylae is multinucleate, lacks mitochondria, and has cones
of microtubules associated with its flagellar kinetosomes. According to
unpublished studies of B r u g e r o 11 e, there are several noncontractile
flagella, each associated with one of the nuclei. In view of this, V i ck
e r m a n believes that Mastigella is a "higher" zooflagellate, but appears
to have no obvious affinities to any particular group. Perhaps,, after
more is known about other members of this genus, a new order might
have to be established for them.
Since nothing is known about the fine-structural details of many
of the other former members of the order RHIZOMASTIGIDA, e.g.,
Heliobodo, Actinomonas, Dimorpha and Pteridomonas, neither V i ck
e r m a n nor I is ready to place them in any known protozoan as-
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