PROGRESS IN PROTOZOOLOGY

206 B. M. HONIGBERG
by light microscopy, were considered sufficient for proposing interrelationships
among the suprafamilial taxa of ciliates. The advent of electron
microscopy in particular (see history in Corliss 1974) has allowed
a revolution not only in taxonomy and classification but also in
our ideas concerning affinities and evolutionary lines among these protozoa.
New methodologies of data analysis are now available (phenetics,
cladistics, etc.) as well as the new technological and cytological approaches:
outstanding examples at this Congress would include Dr. B a r d e-
1 e's precise and patient use of the freeze-fracture technique and Dr.
L y n n's application of his own "Structural Conservatism Hypothesis."
Others have emphasized what the discussant likes to call the "Constellation
of Characters Hypothesis;" Drs. Bar dele and Lynn also
subscribe to this latter approach.
The intriguing case of Stephanopogon can be used as a striking
example of the value of ultrastructural studies and of treating numerous
data by computer analysis. Most of the data Dr. Corliss mentioned
— and the half-dozen slides he showed were results of a study now
being concluded at the University of Maryland by Ms. Diana Lipscomb.
Stephanopogon has, for a whole century, been recognized and classified
as a "relatively simple marine benthic gymnostome ciliate". In
a recent book (Corliss 1979), a new order, PRIMOCILIATIDA, was
even erected for it. Electron microscopical studies, however, reveal that
it not only does not show such major and essentially unique ciliate
characters as pellicular alveoli, parasomal sacs, kinetodesmata, and
transverse and posticiliary ribbons of microtubules (universally associated
with ciliate kinetosomes) but does show such "lower" flagellate
features as mitochondrial cristae that are discoidal, a single kind of
nucleus with single large central endosome or nucleolus (with "promitotic"
type of division), a symmetrogenic mode of fission, a desmose
running between adjacent basal bodies, and a subpellicular sheet of
microtubules. Stephanopogon possesses also some characters found in
both ciliate and flagellate groups, as well as several totally unique
features of its own. A cladistic analysis of 136 characters, as found
(present or absent) in some 34 taxa of flagellated (or ciliated) high-level
protozoan groups, reveals that Stephanopogon belongs in some supraordinal
taxon that also includes both the trypanosomatids (former "lower
zooflagellates") and the euglenids (former "green algae"). (Ms. Lipscomb
and the discussant will be publishing details soon, elsewhere,
including proposal of a unique order for this "ciliate-turned-flagellate.")
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