  We give necessary and sufficient conditions for weak and strong embeddability
of amalgams in each subvariety of the category of all nilpotent groups of class
at most two; this generalizes B. Maier's result for the latter class. We also
discuss dominions (in the sense of Isbell), and characterize the weak, strong,
and special amalgamation bases for each subvariety, contrasting the resulting
classes with one another.
