One extra checkpoint with some extra debugging info before getting into that last issue.
Removing animation of the third "sequential" algorithm as the cell coloring does not handle it properly.
Completing the adjustments to track the minimum spanning tree construction using lists of edges rather than lists of vertices, thereby avoiding recalculation of the distance metric during mst construction.
Final update for initial milestone.  Removing debug console output that produces a useful audit trail of the derivation of an approximation of a minimum distance closed tour from a minimum spanning tree.  While informative, the debug trail is computationally intense and dominates the program's execution time when left in place.  In order to make it easier to restore the debug trail or process its content out of the file altogether, debug-related lines of code are the only ones where a '//' commenting tag appears at the far left, with no preceding whitespace whatsoever.  Every other non-debugging comment has at least two characters of whitespace preceding '//'.