THE PHENOMENA OF MUTATION 187 



cultivated state is in a sense pathological. Such 

 variation doubtless occurs in nature, but not with 

 such luxuriance. The breeds of domestic fowls 

 differ so greatly that Bateson and others refuse to 

 believe that they have all arisen from the single 

 species Gallus bariklva. It seems to me from the 

 evidence that there cannot be any doubt that they 

 have so arisen. One fact that impresses my mind is 

 that if we consider colour variations in domesticated 

 animals, we find that a similar set of colours has 

 arisen in the most diverse kinds of animals with 

 sometimes certain markings or colours peculiar to 

 one group, c.r/. dappling in horses, wing bars in 

 pigeons. Thus in various kinds of Mammals and 

 Birds we have white and black, red or yellow, 

 chocolate with various degrees of dilution, and 

 piebald combinations. Why should forms originally 

 so different, as the cat with its striped markings and 

 the rabbit with no markings at all, give rise to the 

 same colour varieties ? It seems probable that the 

 reason is that the original form had the small number 

 of pigments which occur mixed together in very 

 small particles, and that in the descendants the single 

 pigments have separated out, with increase or 

 decrease in different cases. It is true that historical 

 evidence tends to show that the greatest variations, 

 such as albinism in one direction or excess of 

 pigment in the other in the Sweet Pea, were the first 

 to arise (see Bateson, Presidential Address to British 

 Association, Australia, 1914, Part i.), and the splitting 

 appears often to be intentionally produced by crossing 

 these extreme variations with the original form, but 

 the possibility remains that tlie conditions of domes- 

 tication, abundant food, security and reduced 



