  From a survey of the 3400 A region in the earliest O-type spectra, we have
found that two of the four O2 giants observed in the LMC have the OIV lines
there stronger than the NIV, while the other two have the opposite. A SMC
counterpart also has the NIV stronger than OIV. Inspection of the blue spectra
of these stars shows that the former pair have weaker N lines in all ionization
states (III, IV, V) present as well as lines of CIV lambda 4658, while the
latter three have stronger N lines and greater He/H. Space ultraviolet
observations of two of the N-strong stars show NV wind profiles substantially
stronger than those of CIV, while in the N-weak stars the CIV features are
equal to or stronger than the NV. The N-strong stars are now reclassified as
ON2 III(f*), newly defining that category. These characteristics strongly
suggest a larger fraction of processed material in the atmospheres of the ON2
stars, which we confirm by modeling the optical spectra. In the context of
current models, it is in turn implied that the ON2 stars are in a more advanced
evolutionary state than the others, and/or that they had higher initial
rotational velocities. The recent formulation of the effects of rotation on
massive stellar evolution introduces an additional fundamental parameter, which
the CNO abundances are in principle able to constrain. We present some
illustrative comparisons with current Geneva evolutionary models for rotating
massive stars. It is possible that these very hot, nitrogen-rich objects are
products of homogeneous evolution. Our results will provide motivation for
further physical modeling of the atmospheres and evolutionary histories of the
most massive hot stars.
