Variation, Isolating Mechanisms, and Hybridization in Certain Toads.

On the species problem the interests of genetics, taxonomy, and ecology converge to a remarkable extent, and it seems that only through coordination of the methods of these several disciplines can satisfactory progress in this field be made. Where closely-related species, or populations very nearly attaining the rank of species, are involved, the problem attains a maximum of complexity; it is just such cases, however, which appear most amenable to intensive investigation. The present article reports the results of an attempt to analyze the situation in a group of species of toads inhabiting the eastern United States.