Considering the delicate response of structure to climate, a person naturally questions whether or not natural selection accounts for all of the differences between subspecies. To show that natural selection determines the color of _Mustela frenata_, it would be necessary to assume that climate, color, and utility of color are positively correlated. Although climate (rainfall) and color are correlated in such a manner that three subspecies of weasel in places as far apart as New England, Perú, and the state of Washington are colored alike, other features of the three environments are unlike. Kinds of animals which the weasel catches for food, and flora in which the weasel finds concealment, are dissimiliar. If natural selection alone determined the color, some difference in color would be expected between the weasel which needed to be obliteratively colored, that is camouflaged, the better to catch a _Phyllotis_ in Perú and the weasel in Washington which needed nature's aid in catching _Microtus_. _Mustela frenata goldmani_ of the highlands of southern México, which is known to attack the huge pocket gophers, _Orthogeomys_ and _Cratogeomys_, has a weaker dental armature than _Mustela frenata texensis_ which does not have to overcome prey so formidable as does _goldmani_. Equally formidable enemies endanger _M. f. goldmani_ and _texensis_. Examples of this nature could be multiplied. Without actually proving anything concerning selection, these examples give reason for us to suppose that some characters are not determined by natural selection.