With a view to propagating the spiny lobster, Panulirus japonicus, several measures have been successfully put into force in the Wakayama Prefecture with coöperation of 29 fishery guilds there. But as to biology of the animal there remain many points to be made out. The biological minimum size of th species in the Wakayama Prefecture was determined by the present author to be 150-160cm in length, morphology of the pleopods being used as a critelion to distinguish adult from immature (Fig. 1). Tagged 163 specimens, 66-206cm long, were riberated and seven were recaptured about five months afterwards. Of these seven, five retained the tag (C. von Bonde's tag) in a perfect condition, and their rate of growth was determined as shown in Table 1.
