Modification of the Zeiss-Pulfrich photometer for the measurement of 90° scattering and dissymmetry. Raymund C. Rhees and Joseph F Foster pages 1-14

The Coccinellidae (Coleoptera) of the Upper Mississippi Basin. Curtis W. Wingo pages 15-54

Fish population of a mining pit lake, Marion County, Iowa. C.E. Ruhr pages 55-78

The nature of the sparing phenomenon. I. Activity and nature of hemagglutinin-inhibitor. Elery R. Becker, Thomas M Schwink, and Robert T. Probst pages 79-90

Morphological features of Brachylaima virginianum metacercariae (Trematoda: Brachylaimatidae), and migration route of cercariae in the second intermediate host. Martin J. Ulmer pages 91-104

Differential equations in the distributions of Schwartz. Leslie D. Gates pages 105-111