Source : Webster's Revised Unabridged Dictionary (1913)

Arthrospore \Ar"thro*spore\, n. [Gr. ? joint + E. spore.]
   (Bacteriol.)
   A bacterial resting cell, -- formerly considered a spore, but
   now known to occur even in endosporous bacteria. --
   {Ar`thro*spor"ic}, {Ar*thros"po*rous}, a.

Source : WordNet®

arthrospore
     n 1: a body that resembles a spore but is not an endospore;
          produced by some bacteria
     2: one of a string of thick walled vegetative resting cells
        formed by some algae and fungi