28 which diverge slightly at an angle in the range of 1 u00b0 to 3 u00b0 preferably the trough axis intersects the vertical axis u201c v u201d of each receptacle through which the trough passes the horizontal axis of each trough lies a distance h 1 see fig4 below the top wall that distance may be in the range of 0 1 to 0 5 times the tray height i e 0 1 u2266 h 1 h u2266 0 5 the bottoms of the troughs lie above the bottoms of the receptacles preferably a distance h 2 in the range of 0 1 to 0 5 time the tray height i e 0 1 u2266 h 2 h u2266 0 5 even at the lower limit the bottoms of the troughs are well above the bottoms of the receptacles each receptacle bottom has an inside diameter d and the semicylindrical portion of each trough has an inside diameter d the preferred ratio d d is in the range of 0 4 to 0 6 the dimensions and proportions for a presently most preferred tray are shown in the table below referring again to fig1 one can see that the troughs and peripheral receptacle walls define octagonal mesas 30 between each pair of diagonally adjacent receptacles the mesa tops are preferably coplanar with the top wall the rim.