142 STUDIES IN THE EVOLUTION OF ANIMALS 



coloration in homologous surfaces, viz., the forehead and nose, the 

 body and outer aspect of the legs, and upper surface of the tail are 

 black, and the under surfaces, corresponding with the unarmoured 

 surfaces of the Pangolin, are white. This, in my judgment, means 

 that the ancestor of the Black Buck lost its armour on what are now 

 white surfaces long before it lost it on what are now dark surfaces, 

 so that those had the opportunity of having their pigment 

 modified, 1 and so becoming contrasted by the time the descend- 

 ants wholly lost their armour. And the only thing now left to tell 

 the tale of ancestral armour in many animals is solely this contrast 

 of coloration, which in certain animals still remains, as a survival of 

 a feature which in remote times may probably have been general. 



In the Horse, through innumerable selections, this contrast of 

 upper and lower surfaces has been mostly extinguished, although 

 Horses of a brownish colour are often met with which have the 

 lower surface much lighter than the upper. But it is in the coster- 

 monger's Donkey that a great contrast is visible between the dark 

 back and flanks and white abdomen. In black-and-tan Dogs the 

 contrast between the two surfaces is very marked ; and there are 

 variations in which the contrasted colours of the Dog are tan and 

 ivhite> or black and white. 



It is not improbable that as time goes on all traces of contrast 

 derived from armoured and unarmoured surfaces may disappear, 

 unless maintained for special purposes, either by natural or artificial 

 selection, or unless reversions to ancestral colourings occur. 

 Among domestic animals this obliteration has already largely 

 occurred. In wild animals we see this obliteration in the Lion, the 

 Puma, the Hare, certain Deer, 2 and others. 



1 In the domestic Dog we see how readily the hair pigment is modified, even in one 

 generation, from black to tan, and from black or tan to white. 



2 The young of the Wapiti Deer is spotted, while the adult has no trace of spots. 

 Cervus Canadensis, Science and Art Museum, Edinburgh. 



