Malay Peninsula and Borneo. This bleaching is entirely absent in a large form (R. gigantea), while being present and a very conspicuous feature in the very closely allied form (R. bicolor), although chiefly confined to the body.
In R. affinis (another species) it is general and uniform both on the body and the limbs, and in R. ephippium is almost entirely absent, or, if present, confined, as in the case of the European Squirrel, to the tail only.
To account for changes of this kind as being due merely to the bleaching or wearing of the hairs seems to me hardly a sufficient explanation, for if that were the sole cause there would be no reason why one portion of the animal should bleach more than another. It might be accounted for in some cases, as Mr. Thomas has pointed out in our European Squirrel, by the absence of a moult; but such a solution would hardly hold good in the case of R. bicolor, where the line of demarcation is irregular, and varies in individuals; or again, in the case of R. affinis, where the bleaching, which is general, follows so quickly on the growth of the new pelage that hardly any specimens in unbleached pelage are known in our museums.
It seems to me that the only way to account for these phenomena is to suppose that these hairs must sever their physiological connection with the body, and that, when disconnected, the destructive action of light and weather is able to act; but to thoroughly elucidate this matter microscopical examination of fresh specimens is necessary. My object in this paper is merely to draw attention to the facts.
Apart from this seasonal change by bleaching, there are two other forms of seasonal pelages to be observed. The one, which may be noticed on S. berdinoni, and doubtless many other forms, in which the pelage worn in summer is a much brighter and more intense edition of that worn during the colder portions of the year. Whether the change takes place by abrasion or by moult, I am unable to say—possibly the former, as the dark lateral stripes can be clearly distinguished in the winter pelage, but very much concealed owing to each hair having a dark brown tip. The other seasonal pelage is that in which the brightest phase takes place in winter, and, instead of being a brighter edition of the duller pelage, is markedly distinct. The only two
