92 Colouration in Animals and Plants. 



seems to have been the case in the breast region of Humming Birds, 

 where only the throat is highly coloured. In the Toucans the breast 

 and throat regions are often marked with colour ; but sometimes the 

 hue is the same and the boundaries of the regions marked with a 

 band of another colour; if this boundary band be increased, the 

 regions do not seem so well shown, for the boundary becomes as 

 broad as the area ; yet, in all these cases the dependence upon 

 regional decoration is manifest. No doubt the few uniformly 

 coloured birds were derived from species which were once variously 

 hued ; the gradation of colour being lost in transmission. 



Mammalia. The axial decoration of the mammalia is very 

 definite, and nearly all species have a dorsal tract marked with 

 colour. The dark bands on the back of the horse, ox, and ass, are 

 cases in point. In nearly every case the dorsal is darker than the 

 ventral surface. 



If we take highly decorated species, that is, animals marked by 

 alternate dark and light bands, or spots, such as the zebra, some 

 deer, or the carnivora, we find, first, that the region of the spinal 

 column is marked by a dark stripe (Figs. 9 & 16) ; secondly, that 

 the regions of the appendages, or limbs, are differently marked; 

 thirdly, that the flanks are striped, or spotted, along or between the 

 regions of the lines of the ribs ; fourthly, that the shoulder and hip 

 regions are marked by curved lines ; fifthly, that the pattern 

 changes, and the direction of the lines, or spots, at the head, neck, 

 and every joint of the limbs ; and lastly, that the tips of the ears, 

 nose, tail, and feet, and the eye are emphasized in colour. In 

 spotted animals the greatest length of the spot is generally in the 

 direction of the largest development of the skeleton. 



This morphological arrangement can be traced even when the 

 decoration has been modified. Thus, in the carnivora we have the 

 lion and puma, which live in open country, with plain skins, the 

 tiger with stripes, an inhabitant of the jungle, and the leopard, 

 ocelot, and jaguar with spots, inhabiting the forests. 



But the lion has a dark dorsal stripe, and the nose, etc., are 

 emphasized in colour, and, moreover, the lion has probably lost its 

 marked decoration for protective purposes, for young lions are 

 spotted. The tiger's stripes start from the vertebras, and still 

 follow the lines of the ribs. In the tiger the decoration changes at 

 the neck, and on the head, and the cervical vertebrae are often 

 indicated by seven stripes. See Fig. 5. 



