212 . Colors of West Coast Mammals. _; (zone 
may well be considered as an example of discriminative mark- 
ing. The two species are found in neighboring districts and with- 
out doubt had a common ancestor. If some of the individuals at 
any time became sexually isolated from the remainder, the differenti-. 
tion in the color of the under side of the tail, becoming light in one 
species and dark in the other, would have materially increased the 
prosperity of both races. Directive coloration might have been 
brought to bear upon them at a later stage and accentuated the two 
shades in order to facilitate recognition by their own kind. It must 
be borne in mind, however, that natural selection seems incapable of 
having effected these changes, assuming the validity of the theory — 
that they are recognition markings. 
Prof. Todd has called attention to other uses to which recogni- 
tion markings might be put. Most important of these are such 
markings as enable individuals to recognize one another in the dark- 
ness of their dens or by night. Such markings as these would be 
of practical use in the domestic intercourse between families and in. 
the careof the young. These markings would be in no way of use 
in escaping from danger or in distinguishing one species from an 
allied form; and indeed differ so much in their use from those which. 
have been previously considered as to warrant their being made a sep- 
erate class, which might appropriately be called socialistic markings. 
Prof. Todd mentions a number of examples of this class, including 
among others the skunk, which properly belongs in another division 
which will be considered later. The markings on the head of the 
yellow-bellied marmot ( Arctomys flaviventer ) consisting of a white 
ring around the muzzle, 
in distinct contrast to the ground color, 
would serve to indicate in the dark the position of the head, which — 
would be a great advantage in the social life of the animal in its 
burrow. The black and white patches on the head and the rings on — 
the tail of the racoon ( Procyon lotor ) would serve the same purpose 
of recognition in the dark, as would also the conspicuous white 
spot above the eye and the long, ringed tail of the civet cat ( Bassaris 
astuta). Whether or not the lateral and dorsal streaks of Zamias 
and Sczurus can be accounted for in the same manner cannot be 
answered with as much confidence. e 
i i glassi'in any way except as a recognition 
marking, possibly to mark the position of the body, but why it should 
