66 Zoological Society :— 
streak, which is darker on the back, black on the crown, and indi- 
stinct on the nape; beneath rather paler, with a broad white lon- 
gitudinal streak near the middle of the chest and front of the abdo- 
men; ears produced beyond the fur, naked internally; the skull 
with a very deep concavity between the orbits. 
Hab. Batchian. 
This species is most like Ouscus orientalis; but in that animal the 
male is pure white. It differs entirely from O. celebensis (from 
Celebes) in the general colour of the fur, and in having a distinct 
streak on the head and back, somewhat like the streak on the back 
of the female OC. orientalis, but narrower and darker. 
It differs from ail the other species in the nakedness of the inner 
surface of the ears. 
The white streak on the chest and belly is not exactly in the 
middle of those parts ; and there is a square white spot on the upper 
part of the right fore leg, not found on the other legs. 
This animal may possibly be the coloured male of C. orientalis ; 
but all the known males of that species are pure white. Can albi- 
nism be the usual, and this coloured male the unusual, characteristic 
of that species ? 
The skull of Mr. Wallace’s animal from Batchian agrees in general 
character with the skull of C. orientalis (sent to the Museum as 
Cuscus Quoyii from the Moluccas), but is yet sufficiently unlike to 
render it very doubtful if it be not a distinct species. It is smaller ; 
the impression on the crown is deeper and furnished with a much 
more decidedly raised edge, which is extended behind on the central 
line to the occiput ; and there is a notch or ridge at the upper front 
angle of the orbit, not to be found on the skull of C. orientalis. 
Some of the converts to the theory of the mutation of species 
may think that this animal is an instance in point; but such a hy- 
pothesis derives no support from the observations I have made. 
All the difficulties here started arise from the imperfect material 
which the specimen affords for arriving at any definite opinion on the 
subject ; and I believe that this is the explanation of nine-tenths, or 
I may say ninety-nine in a hundred, of the cases on which the theory 
is attempted to be established. This is not to be wondered at when 
we consider how very few are the animals, even of our own coun- 
try, and more especially of exotic species and genera, whose history 
and anatomy have been properly studied. Most naturalists are of 
necessity in the habit of describing species from the few specimens 
which are brought from abroad in a more or less perfect state, with- 
out being acquainted with the changes which the animal undergoes 
in growing from its birth to maturity, and without the slightest in- 
dication of its habits and manners. Now, we know from experience 
amongst the British birds (such for example as the Rook and the 
Crow, and the species of the Willow Wrens), that if we were called 
on to describe them from such materials we might make great mis- 
takes. A mere examination of stuffed specimens might well lead 
to doubts as to their distinctness as species, but this could never 
be the case if we had seen them alive in their native haunts, and 
