Motile bacteria: Note diffuse appearance of growth within the medium.  For some bacteria the turbidity may become uniform through the medium and hard to see if you wait too long before making observations.  However, see discussion of obligate aerobes below.

Nonmotile bacteria:  Note the sharp delimitation of the bacterial growth along the path of inoculation.

Obligate aerobes:  Bacteria that cannot grow in the absence of oxygen will not grow very deeply into the medium, which becomes anaerobic a short distance below the surface.  While growth of bacteria on the surface of the medium in not uncommon for many species, obligate aerobes will only grow on the surface of the medium and show little growth in the medium.  It may not be possible to interpret the motility.