Transmission of Demodex canis Leydig to pups. Frank E. French, Earle S. Raun and Durwood L. Baker. 291

Kinetics of the tin(ii) reduction of some ferricinium ions. Frederick R. Duke and Walter W. Lawrence. 299

Blood lactic acid concentration of unexercised and exercised mature carp in winter and summer. Carl W. Caillouet, Jr. 309

Theoretical equations for ultracentrifugal molecular weight determinations of polyelectrolytes. Stig R. Erlander. 323

Scotch pine provenance trial in northeast Iowa. K.F. Jensen and G.E. Gatherum. 377

Ascorbic acid assay by a specific enzymatic method. Michael W. Rathke and Frederick G. Smith. 385

Japanese larch provenance trial in northeast Iowa. J.E. Kepler and G.E. Gatherum. 393