TEGUMENTARY STRUCTURES 9 
a bright crimson. The most general colours are various shades of 
gray, brown, and tawny, with a frequent tendency to whiteness of 
the ventral surface of the body ; but among the Squirrels, and more 
especially those provided with a parachute for flying, we find brilliant 
russets, passing into orange and red. Dark brown or black is also 
“not very uncommon, as in the Bears and the Sable Antelope of 
South Africa. Entirely white mammals are rare, and mostly 
characteristic of the polar regions, or of countries having a long 
and snowy winter. An entirely white Bat (Diclidwrus albus) occurs, 
however, in South America. In the large majority of mammals 
that exhibit a varied coloration, the upper and most exposed parts 
of the surface present the richest and darkest colours, the under 
parts being pale or often quite white. The Ratels, Gluttons, 4lurus, 
Hamsters, and some others are exceptions to this rule. A large 
number of mammals having a ground colour of gray, tawny, or dun 
are marked by stripes or spots, which are generally of a darker hue 
than the ground colour, as in many Carnivora, but more rarely are 
lighter, as in the Fallow and Axis Deer and several species of Ante- 
lope. These stripes very generally run transversely to the axis of the 
body, as in the Tasmanian Thylacine, the Tiger, and the Zebra; but 
they may be longitudinal, as in several of the Civet family. There has 
been considerable discussion as to whether the striped or the spotted 
is the more primitive type of coloration; but no very conclusive 
arguments have been brought forward in favour of either view. It 
is, however, manifest that in several groups of mammals there is a 
tendency to lose the spots, and more rarely the stripes, and to 
assume a uniform colour. Thus the young of nearly all the species 
of Deer are spotted, whereas the adults of only the Fallow and 
Axis Deer are so marked. The same is true of most of the Pigs ; 
and the young of the Malayan and American Tapirs are marked 
by light-coloured stripes and spots on a dark ground. In like 
manner the young of the Lion and the Puma exhibit distinct spots 
which disappear with advancing age. In most of our domestic 
horses of various shades of bay and brown we may detect “‘ dappling ” 
on the under hair when the outer coat has been removed, which 
is not apparent on the surface of the latter. Many varieties of 
the Ass and the Horse also exhibit a tendency to the presence of 
stripes on the legs, which would seem to indicate a descent from a 
striped Zebra-like type. 
A peculiar feature, which is, however, common to many other 
groups of animals, is the tendency to what is known as melanism, 
or the production of black or dark individuals or races of particular 
species, due to an excess of pigment in the skin and hair. Thus we 
may have black Leopards and Jaguars, black Wolves, and black 
Rabbits. 
The opposite to melanism, and of more frequent occurrence, is 
