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Paper text:
we have published kinematical observations of 20 des in @xcite .
they were obtained at the carelec long - slit spectrograph attached to the 2-m telescope of the observatoire de haute - provence .
figure 1 presents two typical velocity profiles : those of ngc 205 ( extending out to 5 arcmin ) , and ic 3328 , a virgo - cluster de .
the kinematical profiles , extending beyond one effective radius , reveal significant rotation in all our candidate objects .
a similar result is presented in @xcite .    from these and other sources ,
we have selected 14 galaxies with reliable kinematical measurements .
we did not include four of the faint virgo dwarfs observed by @xcite , where no rotation was detected , because the profiles extend to only a fraction of the effective radius ; experience from past observations reveals that extrapolations of central profiles is hazardous .
for more than 10 years , de galaxies were though to be flattened by anisotropy @xcite .
because new observations extend farther out , more rotation can be detected .
since des feature roughly exponential photometric profiles , we can not apply directly the @xmath0 anisotropy test @xcite , which is adapted to the case of @xmath1 profiles .
we thus developed a simple isotropic dynamical model as in @xcite , but for a @xmath2 profile @xcite .
letting @xmath3 be the semi - major axis of an isophote ( with @xmath4 corresponding to the effective isophote ) , figure 2 presents typical normalized rotation curves for @xmath5 and @xmath6 .
the model shows that the maximum rotation is expected at @xmath7 for a de ( @xmath5 or 2 ) , compared to @xmath8 for an elliptical ( @xmath6 ) . and
for a de , the expected @xmath9 ratio ( where @xmath10 is the peak central velocity dispersion ) is 10@xmath1120 % larger than for a normal e.        figure 3 shows the kinematic test for our data supplemented by other sources .
most galaxies are compatible with being rotationally supported .
the two flattest objects , ic 3393 and ic 3773 , bear large error bars but do not seem incompatible with isotropy .
other interesting cases are ngc 205 and ic 794 . despite the significant rotation
we have found , the former is unlikely to be isotropic ; and the latter is certainly anisotropic .
several similarities do exist between e and de galaxies : a ) there is a continuum in the surface brightness _ versus _ luminosity diagram @xcite , b ) there is a transition in the shape of the photometric profile and , c ) on taking into account the difference in stellar populations @xcite , the de galaxies lie on the fundamental plane of ellipticals .
these characteristics , however , reflect equilibrium relations and do not necessarily imply a common origin .
conversely , the difference in clustering properties of the two classes is a clue for different origins .
the new kinematical observations imply that the de progenitors are probably rotating dirr systems and low - mass , late - type spirals . as in the dekel et al .
scenario , the intrinsic low - mass of the progenitors may result in an important mass loss due to the sn - driven winds , and this may explains their low metallicity .
in addition , the ram pressure against the hot intergalactic medium strips off the residual neutral gas . dynamical harassment from encounters with massive galaxies , which predicts anisotropic objects @xcite , does not appear to represent a key factor for these des , but ram pressure stripping of the gas may have helped to stop the star formation .
a few interesting objects deserve additional comments .
ngc 205 may own its anisotropy to its interaction with m 31 @xcite .
but we note that the relevance of the diagnostic may be questioned , since the observed kinematics fail to fit the isotropic model with a constant _
m / l _ ratio .
ic 794 is particularly interesting . as noted by pedraz et al . , it is strongly anisotropic , young , and metal rich .
these characteristics make it a good candidate for being a tidal dwarf issued from enriched material after a major collision involving a spiral .
we have no information on the stellar content of ic 3344 , the other anisotropic object of @xcite , which may be similar to ic 794 ( both lie in center of the virgo cluster ) .
the other galaxies where @xcite did not detect rotation are fainter ; they may have been more sensitive to environment and predisposed to anisotropy . but
observations extending to larger radii are needed to conclude .
new observations show that most of the flattened diffuse elliptical ( de ) galaxies are essentially isotropic rotators . 
 this supports the idea that des have evolved from fast rotating dirr systems or late - type spirals after their gas was expelled by sn - driven winds and stripped by ram pressure against the intergalactic medium .