TEGUMEA'TARY STRUCTURES 



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 (Diclidurus alius) 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 Katels, Gluttons, jElurus, 

 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 Ave 

 may have black Leopards and Jaguars, black Wolves, and black 

 Rabbits. 



The opposite to melanism, and of more frequent occurrence, is 



