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Show 1886.] THE HUME COLLECTION. 77 the greater prevalence and greater intensity of the red colour of belly in the northern Malay specimens as compared with the southern ones, and by the absence of white-and-yellow bellied specimens among the mainland series as compared with those from Sumatra, Java, and Borneo. Blue-bellied specimens seem to be proportionately most numerous in the Johore region, our series of seven from there having no less than five of that tint, while of nineteen from Salangore only one single specimen is blue-bellied, the others all having the rich rufous bellies characteristic of most mainland specimens. On the other hand, in insular specimens, the red, when present, is generally paler and poorer in tone, and is commonly replaced either by yellow, white, or, as in the mainland series, by blue. No definable varieties, however, can be made out, as in any given locality specimens are found belonging to several of the different forms ; intermediate ones also are by no means rare; thus the Museum specimen No. 49. 1. 8. 5, from Java, is marked with mingled patches of blue and white on the belly, and the white of others is led up to from the deepest rufous through various shades of red and yellow. Red-bellied specimens have in all cases red-tipped tails, while white-and yellow-bellied ones have the tip annulated like the rest of the tail. With regard to the influences that cause these very remarkable variations, it would seem as if there were some property in mammals (ending occasionally to the production of red-tinted varieties in a somewhat erratic manner, comparable to the way in which albinistic and melanistic varieties are produced. The striking fact that all the red-bellied specimens of S. badging, and the red-bellied specimens only, have red-tipped tails, is by itself a sign that the red is produced by something which affects the whole animal, and is not merely a colour put on to a particular part for sexual or protective purposes, as is usually the case. Albinistic and melanistic varieties are well known to occur much more frequently in some localities than in others1; and in the same way what may be termed " erythrism " seems in some places to succeed to such an extent that red specimens are in the majority, although a tendency still remains for the production of such atavistic non-rufous individuals as the blue-bellied specimens to which the name of S. nigrovittatus has been applied. This theory of " erythrism " is not suggested to account for the present case only, there being many other instances in which the presence of red colour has turned out to be exceedingly deceptive as a specific character, and in which the red of usually red-marked species has been found to have a way of disappearing unaccountably, while more or less red-tinted individuals of grey species are by uo means unknown. Erythrism is particularly common among the Mungooses, and is responsible for a large number of the untenable species which have been formed in that group. I can find no reliable evidence of the occurrence of &. badging 1 Notably in the case of the black specimens of Arvicola amphibius from Scotland, or, in this very region and group, in the remarkable case of Sauries ferrugineusgermaini, M.-Edw., a permanently black geographical race inhabiting the island of Pulo Condor. (See Milne-Edwards, Eev. Mag. Zool. 1867, p. 193 ) |
