1886. ] THE HUME COLLECTION. 77 
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 ant 
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 
tending 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 itselfa 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 
kuown 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. badging 
? 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 Sewrus 
ferrugineus germaini, M.-Edw., a permanently black geographical race inhabitin 
the island of Pulo Condor. (See Milne-Edwards, Rev. Mag. Zool. 1867, p. 193.) 
