  We investigate by the use of the Martin - Siggia - Rose generating functional
technique and the self - consistent Hartree approximation, the dynamics of the
ring homopolymer collapse (swelling) following an instantaneous change into a
poor (good) solvent conditions.The equation of motion for the time dependent
monomer - to - monomer correlation function is systematically derived. It is
argued that for describing of the coarse - graining process (which neglects the
capillary instability and the coalescence of ``pearls'') the Rouse mode
representation is very helpful, so that the resulting equations of motion can
be simply solved numerically. In the case of the collapse this solution is
analyzed in the framework of the hierarchically crumpled fractal picture, with
crumples of successively growing scale along the chain. The presented numerical
results are in line with the corresponding simple scaling argumentation which
in particular shows that the characteristic collapse time of a segment of
length $g$ scales as $t^* \sim \zeta_0 g/\tau$ (where $\zeta_0$ is a bare
friction coefficient and $\tau$ is a depth of quench). In contrast to the
collapse the globule swelling can be seen (in the case that topological effects
are neglected) as a homogeneous expansion of the globule interior. The swelling
of each Rouse mode as well as gyration radius $R_g$ is discussed.
