VARIATION. 113 



specific variation or of any tendency thereto. 

 The Siamese Twins were a specific variation, 

 but common- sense cannot accept such mon- 

 strosities as evidence of the evolution of a 

 new species. 



There was recently to be seen in Bristol a 

 mare born minus a foreleg and shoulder ; she 

 was nevertheless reared, and, as certified, had 

 produced three foals, two of them winners of 

 prizes for fast trotting, demonstrating in the 

 most conclusive manner that her deviation 

 from the normal type neither was trans- 

 mitted to her progeny, nor indicated any 

 tendency to specific variation. 



Specific Variation. 



We have now to consider those differences 

 in structure and organisation that are the dis- 

 tinguishing characteristics of distinct races, 

 and constitute " specific variation." 



According to Darwin, specific variation 

 originated in slight beneficial differences 

 among members of the same race ; and 

 these differences accumulating, chiefly by 

 the effects of the struggle for existence, 

 during numberless successive generations, 

 ultimately formed new species. Speaking 

 metaphorically, evolution advanced along 



H 



