RELATIONSHIP OF ARMADILLO TO OTHER MAMMALS 227 



framework of bone the lines on which the animal world was there- 

 after to be ruled. 



It would be idle to suppose that the bony-plates of the Arma- 

 dillo, the hide-plates of the Rhinoceros, and the picture-plates of 

 the Horse, are all so like each other by mere accident, any more 

 than we can consider that the seven cervical vertebrae of these 

 animals came to them all by accident. One can fully understand 

 that the external features of an animal are subject to much greater 

 variations than the internal skeleton ; nevertheless, in spite of all 

 the modifications in the skin, which the animal unconsciously 

 brought about in order to adapt itself to its surroundings, enough 

 is left in the skin features of many species to assure us that all 

 these animals have had a common origin, and that they descended 

 from an armour-clad ancestry. The evidence of the pictures on the 

 skin of the Jaguar, as I have shown, is too clear to admit of any 

 other interpretation than that of descent from armour-plating. 



I have said enough to prove that the markings on the skins of 

 mammals are not necessarily the result of natural selection, work- 

 ing gradually on some incipient variation through long periods of 

 time ; but more probably the result of an inherited nerve-centre 

 habit. Then, after the total disappearance of calcareous matter 

 from the skin, this habit continued its action on the pigments of 

 the skin, and was modified subsequently in a hundred ways. 

 What natural selection probably did do was, as I said, to maintain 

 this inherited skin feature, wherever it was advantageous to the 

 animal, and to obliterate it wherever it was not. 



From all this wearisome discussion we learn one great lesson, 

 and it is this : that habits, or memories, of the nervous system, 

 when established for long ages, are got rid of very slowly ; and that 

 it requires more long ages for ne^v ones to become established in 

 their places. 



