The glucose uptake rate by plerocercoid of Diphyllobothrium sp. was a mean value of 5.35 +/- 0.80 micro moles/hr/g of wet wt, and total CO2 production rates by the plerocercoid larva averaged 7.54 +/- 0.73 micro moles/hr/g of wet wt. The relative specific activity into respiratory CO2 showed a mean value of 7.30 +/- 0.90 per cent. The rate of CO2 production derived from medium C(14)-glucose was a mean of 0.58 +/- 0.13 micro moles/hr/g of wet wt. Therefore, the average value of 1.92 +/- 0.38 per cent(R.G.D(CO2) of glucose utilized by the larvae from the medium C(14)-glucose was oxidized to respiratory CO2. 2. The tissue concentration of glycogen in plerocercoid larva was a mean of 46.28 +/- 2.23 mg/g or 4.63 +/- 0.22 per cent/g of wet wt., and the turnover rate of glycogen pool was a mean of 0.049 +/- 0.012 %/hr or 0.010 +/- 0.003 mg/hr/g of wet wt. The average value of 2.76 +/- 1.00 per cent of glucose utilized by the larvae from the medium C(14)-glucose was incorporated to the glycogen. 3. These data accounts for that only 5 per cent of the utilized glucose by the plerocercoid larvae participated in furnishing the oxidation into respiratory CO2 and the synthetic process into glycogen.
