  The far-infrared c-axis conductivity of flux-grown
Y$_{1-x}$Pr$_{x}$Ba$_{2}$Cu$_{3}$O$_{7}$ single crystals with 0.2$\leq $x$\leq
$0.5 has been studied by sepectral ellipsometry. We find that the c-axis
response exhibits spectral features similar to deoxygenated underdoped
YBa$_{2}$Cu$_{3}$O$_{7-\delta}$, i.e., a pseudogap develops in the normal
state, the phonon mode at 320 cm$^{-1}$ exhibits an anomalous T-dependence and
an additional absorption peak forms at T. This suggests that the T$_{c}$
suppression in flux grown Pr-substituted crystals is caused by a decrease of
the hole content and/or by carrier localization rather than by pair breaking.
