This memo is about mechanical arms. The literature on robotics seems to be deficient in such discussions, perhaps because not enough sharp theoretical problems have been formulated to attract interest. I"m sure many of these matters have been discussed in other literatures-- prosthetics, orthopedics, mechanical engineering, etc., and references to such discussions would be welcome. We raise these issues in the context of designing the mini-robot" system in the A.I. Laboratory in 1972-1973. But we would like to attract the interests of the general heuristic programming community to such questions.