AN EXTRA CLAW ON THE FIRST AND ON THE 3RD CHELIPED OF THE CRAYFISH, PROCAMBARUS-CLARKII (DECAPODA, CAMBARIDAE)

Two live crayfish, one with an extra claw on a first, and another with an extra claw on a third cheliped, were obtained. Each extra claw dev eloped from the base of a primary propodus with mirror-image symmetry. Both extra dactyls were movable. However, the extra claw on the first cheliped was usually in a closed position, while that on the third wa s in the opened position. The crayfish did not voluntarily swing the e xtra dactyl. There were muscles and nerves in the extra claws, but the y might not: have been complete for a claw. Some of the nerve fibers w ere supplied to the extra claw from the primary nerve bundles. The ext ra claw might have been formed as the complementary image of the prima ry claw.