  We present spectral observations of 130 young stellar objects (YSOs) in the
Serpens Cloud Core and NGC 1333 embedded clusters. The observations consist of
near-IR spectra in the H and K-bands, from SpeX on the IRTF and far-red spectra
(6000 - 9000 A) from Hectospec on the MMT. These YSOs were identified in
previous Spitzer and Chandra observations, and the evolutionary classes of the
YSOs were determined from the Spitzer mid-IR photometry. With these spectra, we
search for corroborating evidence for the pre-main sequence nature of the
objects, study the properties of the detected emission lines as a function of
evolutionary class, and obtain spectral types for the observed YSOs. By
comparing the positions of the YSOs in the HR diagrams with the pre-main
sequence tracks of Baraffe (1998), we determine ages of the embedded sources
and study the relative ages of the YSOs with and without optically thick
circumstellar disks. The apparent isochronal ages of the YSOs in both clusters
range from less than 1 Myr to 10 Myr, with most objects below 3 Myr. The
observed distribution of ages for the Class II and Class III objects are
statistically indistinguishable. We examine the spatial distribution and
extinction of the YSOs as a function of their isochronal ages. We find the
sources < 3 Myr to be concentrated in the molecular cloud gas while the older
sources are spatially dispersed and are not deeply embedded. Nonetheless, the
sources with isochronal ages > 3 Myr show all the characteristics of young
stellar objects in their spectra, their IR spectral energy distributions, and
their X-ray emission.
