Abstract California has an enormous stake in the Colorado River. In the southern portion of the State, 80 percent of the water used is furnished by the Colorado River, and this area needs still more water in the immediate years ahead. But it cannot get more from the natural supply of the Colorado. T

The Drosophila virilis species group offers valuable opportunities for studying the roles of chromosomal re-arrangements and mating signals in speciation. The 13 species are divided into two subgroups, the montana and virilis ‘phylads’. There is greater differentiation among species within the monta