There is a marked tendency for intergrades between a light-colored subspecies, such as _D. o. celeripes_, and a dark-colored kind, such as _D. o. utahensis_, to show varying degrees of blending in color. The insular population, _D. o. compactus_, has, however, two distinct color phases, a light phase and a slightly darker phase, and shows no tendency toward blending. In other kinds of mammals, blending of color is known to be the result of the action of multiple alleles, but in the insular kangaroo rat (_D. o. compactus_) the color appears to be the result of either a reduced multiple allelomorphic complex or even a unit factor. The two color phases of this insular subspecies, which might be an expression of a unit factor, more probably are specializations in which the multiple alleles for color have been reduced. The probability that there is either a unit factor or a reduced number of alleles at work is suggested by the taking of more dark-colored than light-colored animals and by the absence of blending of color. This insular population has undoubtedly been derived from the mainland kangaroo rat, _D. o. sennetti_, which has the usual range of variation but, to my knowledge, there are no individuals of _D. o. sennetti_ so light as the darkest animals of _D. o. compactus_ from the islands. Populations from a given locality are remarkably stable in color except the animals from Samalayuca, Chihuahua, which vary in color from individuals almost as light as _D. o. compactus_ to animals that approach _D. o. ordii_ in darkness of pelage. The subspecies of _D. ordii_ show no noticeable variation in the extent of the hip stripe, supraorbital and postauricular spots, basal white ring of the tail, lateral stripes of the tail or the extent of white on the venter and feet. There is, however, variation in the degree and extent of the arietiform facial markings. In _Dipodomys ordii utahensis_, _D. o. cupidineus_, _D. o. obscurus_ and _D. o. fuscus_ these markings are pronounced. In _D. o. celeripes_, _D. o. pallidus_, _D. o. compactus_ and _D. o. attenuatus_ these markings are either obliterated or nearly so.