  (Abridged) We report on ten weeks of RXTE observations of the X-ray transient
XTE J1701-462. Comparisons with other sources suggest it had all the
characteristics of the neutron star Z sources (the brightest persistent neutron
star LMXBs). These include Z tracks in X-ray color diagrams and typical
variability components detected in the power spectra. XTE J1701-462 is the
first transient Z source and provides unique insights into mass accretion rate
(Mdot) and luminosity dependencies in neutron star LMXBs. As its overall
luminosity decreased, we observed a switch between two types of Z-source
behavior, with most of the branches of the Z-track changing their shape and/or
orientation. We interpret this switch as an extreme case of the longterm
changes seen in the persistent Z sources and suggest that these result from
changes in Mdot. We also suggest that the Cyg-like Z sources (Cyg X-2, GX 5-1,
and GX 340+0) might be more luminous (> 50%) than the Sco-like Z sources (Sco
X-1, GX 17+2, and GX 349+2). Adopting a possible explanation for the behavior
of kHz QPOs, which involves a prompt as well as a filtered response to changes
in Mdot, we propose that changes in Mdot can explain both movement along the Z
track and changes in the shape of the Z track. We discuss some consequences of
this and consider the possibility that the branches of the Z will evolve into
the branches observed in the X-ray color diagrams of the less luminous atoll
sources, but not in a way that was previously suggested.
