The failure of exchange between Vitamin B_12r and radioactive cobalt chloride. Harvey Diehl and Adolf Voigt. 471

Chemoautotrophic fixation of carbon dioxide by Thiobacillus thiooxidans. Isamu Suzuki and C.H. Werkman 475

Soil erodibility and other physical properties of some Iowa soils. John E. Ada,s, Don Kirkham, and Wayne H. Scholtes 485

A culture apparatus suitable for performance of presumptive test for the coliform group under field conditions. Loyd Y. Quinn 541

Responses of some minnows to flood and drought conditions in an intermittent stream. Andreas A. Paloumpis 547

Movements of channel catfish in Des Moines River, Boone County, Iowa. R.Jess Muncy 563