EXTENSIONS OF DARWINISM 275 



increasing through the law of germinal selection, and has 

 thus become useless to the existing animal. 



The other case is that of the equally remarkable 

 Babirusa of the islands of Celebes and Buru, in which the 

 canines of the males are so developed as to be useless for 

 righting (see Fig. 107). Here, too, there can be little 

 doubt that the tusks were originally of the same type as in 

 the wild boar, and were used for both attack and defence ; 

 but the ancestral form having been long isolated in a 



FIG. 107. HEAD OF BABIRUSA (Babirusa alfurus), 



The tusks of this animal continue growing during life. Those of the upper jaw 

 are directed upward from the base so that they do not enter the mouth, but 

 piercing the skin of the face, resemble horns rather than teeth, and curve 

 backwards and downwards. (Flower, Study of Mammals.) 



country where there were no enemies of importance, 

 natural selection ceased to preserve them in their original 

 useful form, and the initial curvature became increased by 

 germinal selection, while natural selection only checked such 

 developments as would be injurious to the individuals which 

 exhibited them. 



A Wider Application of the Principle of Germ- Selection 



But it seems to me that the principle here suggested 

 has a still higher importance, inasmuch as it has been the 

 normal means of adding to and intensifying that endless 

 variety of form, that strange luxuriance of outgrowths, and 

 that exquisite beauty of marking and brilliancy of colour, 



