Subjet Multiplicity in Quark and Gluon Jets at Dzero

We measure the subjet multiplicity M in jets reconstructed with a successive combination type of jet algorithm (kT). We select jets with 55<pT<100 GeV and |eta|<0.5. We compare similar samples of jets at sqrt(s)=1800 and 630 GeV. The HERWIG Monte Carlo simulation predicts that 59% of the jets are gluon jets at sqrt(s)=1800 GeV, and 33% at sqrt(s)=630 GeV. Using this information, we extract the subjet multiplicity in quark (Mq) and gluon (Mg) jets. We also measure the ratio R= (<Mg> -1)/(<Mq>-1)= 1.84 +- 0.15(stat) +0.22-0.18(sys).