188G.] THE HUME COLLECTION. 11 



the greater prevalence and greater intensity of the red colour of the 

 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- 

 belhed specimens have in all cases red-tipped tails, while white-aud 

 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. hadging, 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 x)ut 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 

 others ' ; 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 pro- 

 duction 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 no 

 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 S. budging 



^ Notably in the case of tbe black specimens of Arvicola amphibius from 

 Scotland, or, in this very region and group, in the remarkable case of Sciurus 

 ferrugineus germaini, M.-Edw., a permanently black geographical race inhabiting 

 the island of Pulo Condor. (See Milne- Edwards, Eev. Mag. Zool. 1867, p. 193.) 



