March, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



373 



tips.* Should it get still lighter, the hairs will be 

 found to be annulated with pale red until finally one 

 may get the hair of a dirty creamy white, showing no 

 trace of colour whatever. This is pure " bleaching," 

 possibly a thinning of the pigment, which may be with- 

 drawn for the use of the body as has been stated to 

 take place in the whitening of the Arctic haret. 



Let us now take a nearly allied species from the 

 Natuna Islands off Borneo, R. bungm-ancnsis, and here 

 we find the whole of the body of a brownish colour with 

 rufous annulations, while the under parts are uniformly 

 dark ferruginous, but almost immediately a new coat 

 is assumed we find a patch on cither thigh bleaching, 

 which process rapidly spreads until the whole body is 

 light buff ; the under parts, however, not being affected 

 to the same extent. 



On the mainland of Borneo we have another species, 

 R. ephippium, noticeable for its purity of coloration, 

 very few of the hairs having subterminal annulations. 

 From the top of the head to the root of the tail runs a 

 broad and very dark brown stripe, slightly lighter on 

 the shoulders and spreading out over the posterior 

 part of the body; the rest of the flanks, sides of the 

 neck, face and ears, ferruginous, fading into pale 

 orange on the limbs, feet, and throat, the colour being 

 palest on the forehead. 



In R. bnramemis, a local form of the above, we find 

 the colour practically the same but lighter. Thus, 

 along the back, we find the majority of the hairs with 

 light annulations, instead of being self-coloured, 

 though self-coloured hairs are still to be found along 

 the back and across the rump. The rufous colour has 

 disappeared from the sides of the body except on the 

 cheeks, and the limbs and feet are yellow. 



In R. af finis, a species from the south of the Malay 

 Peninsula, the new coat is very light brown all over 

 with still paler annulations, which almost immediately 

 bleach to pale yellow. | 



We find, therefore, that we have in R. bicolor a 

 species which in a new coat is pure black, but a species 

 which, owing to bleaching, becomes very variable with 

 light patches on various parts of its body, and, further, 

 that other ncu'ly allied species will have their colour 

 perman<'ntly differentiated in lines and patches situated 

 in places simil.nr to those in which R. bicolor 

 " bleaches. " 



Now, although in 7?. bicolor the amount of " bleach- 

 ing " among various individuals may vary, yet the 

 light-coloured patches will all start from certain definite 

 "centres of bleaching," where "bleaching" will 

 always first show itself, though it need not necessarily 

 take place in all of them at the same time. 



These parts of the htniy, -a'hich are " centres of bleaching," 

 I propose to call " poecilomeres. ' 



• .Although rattier beside tlie point it may malvs the matter clearer 

 if I explain tliat in most animals the colours belong to one of two 

 series, the actual sliade of colour depending on ihe amount and 

 concentration of the pigment. The series are : — (a) White, clay, 

 light brown, dark brown, black (zoomelaiun). (/>) White, yello>«[ 

 orange, red (zooerythrin), and in a very concentrated form,' black. 

 It will thus he noticed that black may be apparent from either of 

 theseseries. This will, I think, lend to explain " erythrism," a 

 common variation among squirrels where they tend to become red, 

 and will account in this species for red tips appearing on the black 

 hairs when they begin to lighten. It also affords an explanation 

 as to why the allied species tend to be red and white in their general 

 coloration, e.g. S, caroli rather than black and yel ow as in 

 R. bicolor. 



t Barretl-Hamillott. Loc. cit.—-p. 307. 



; For full descriptions of these species as well as of some to be 

 mentioned hereafter see my papers in Ann. and Mag. Nat. Hist., 

 ?er. 7, Vol. 5— p. 490 (igoo), and Ser. 7, Vol. 7, pp. 167, 160 (1901). 



The " poecilomeres," so far as R. bicolor is con- 

 cerned, are situated as follows : — 



The shoidders and thighs. 



The crown of the head. 



The tip of the nose and lips. 



The tip of the tail. 



In true R. bicolor one may find all variations. Some- 

 times the lightening process will start at the crown of 

 the head and spread gradually over the back, becoming 

 quite light across the shoulders and darker on the 

 after part of the back, leaving the feet and legs black. 

 .At other times, starting from the shoulders and thighs, 

 the bleaching will spread down the legs, leaving the 

 body black and the legs light, the reverse of the previ- 

 ous case, or, sometimes, owing to the thigh poecilomcre 

 spreading forwards, a narrow light line will be formed 

 between the colour of the back and the under parts. 



In Scinrus rufonigcr, a Sumatran squirrel of the 

 S. erythrccus group, we find this thigh bleaching rather 

 more restricted and leaving a dark line of the colour of 

 the upper parts between the " bleached " portion and 

 the under parts. In this case we see, therefore, the 

 beginnings of a dark as well as a light lateral line. 



Now suppose, instead of these changes taking place 

 during the life of the animal, that they should have 

 become fixed and that the animal is, in consequence, 

 born with a so-to-speak " bleached " pelage. The hair 

 will not, strictiv speaking, be " bleached," but it will 

 differ in colour from the remainder of the body in the 

 places where the poecilomeres should be. Scii/nis 

 prcvostii arid Scitiriis caroli form very good examples 

 among the squirrels, but the matter may be carried 

 further than that; the white and black lateral stripes 

 of the antelopes, the white lips of the same group, the 

 white " blaze " of domestic horses and cattle, the white 

 lips and feet of man}' ungulates, the starting point of 

 the white back of skunks and ratels, the reddish thighs 

 of some African jackals, white legs of the fox and 

 polecat, light mu>;zles of many bears, light frontal 

 patch of Bos frontalis; and among birds, to note but a 

 few, the light patch above the beak of the white-fronted 

 goose and the scaup duck, yellow on the crown of the 

 goldcrest and manv tyrants, light wings of pheasants, 

 &c. Examples might be multiplied for ever, but enough 

 has, I think, been said to show that these " poecilo- 

 meres " arc of sufficiently wide occurrence to render it 

 practically certain that they are due to something more 

 than mere coincidence, and I suggest that we see their 

 earliest beginnings in the "bleaching" of Ralufa. 



As we examine more specimens it will be found that 

 although some of these " poecilomeres " may be traced 

 in almost all species th.it are not self-coloured, they 

 will not always be lighter in colour than the rest of the 

 body, but often, on the contrary, spots of more intense 

 coloration, e.g., buttocks of many monkeys, shoulders 

 of the panda, forehead of okapi, red " blaze " of the 

 goldfinch, red on occiput of many woodpeckers, &c. 



We cannot give a thoroughly satisfactory explanation 

 of this at present, but if it be once thoroughly estab- 

 lished that (as Prof. Metchinikoff and Mr. Barcroft 

 have proved for man, the dog, and the hare) colour 

 may be, and is, extracted from the hair for the use of 

 the body, it is only natural to suppose that any super- 

 fluous colour (supposing the pigment to be of nutritive 

 value to the body) would be stored up where it might 

 most easily be got at, should the body require it. 

 Much more information is, however, required before 

 this can be positivjly stated. 



[To he continued.) 



