108 DARWINISM AND HUMAN LIFE 



sudden emergences of qualitatively new characters, 

 but several cases have been reported. Thus pink 

 katydids may abruptly appear among green ones, 

 and short-winged insects in a long-winged race, 

 in both cases without intergrades. Mutations are 

 also described among freshwater fishes and among 

 medusae. 



When we turn, however, to domesticated animals, 

 where we have greater opportunities of intimate 

 observation, the case for mutation becomes 

 stronger. There are sudden negative changes 

 the entire dropping out of a character as seen in 

 the abrupt appearance of hornless cattle, sheep, and 

 goats, of hairless dogs and horses, of tailless cats 

 and dogs. There are also sudden positive changes 

 the acquisition of a new character such as the 

 appearance of extra digits in poultry and pigs. 

 Those who have bred birds are familiar with such 

 sports, which are often striking. There is evidence 

 in a number of cases that stable and successful 

 breeds have been established, not by the slow 

 increase of minute fluctuations, but by getting a 

 big start in a mutation. In many cases, although 

 breeding or cultivation has grafted the novelty on to 

 a strong stock and made it prepotent, it has not 

 greatly increased the magnitude of the quality 

 which the original sport exhibited. 



DARWIN'S POSITION IN REGARD TO MUTATIONS. 

 Though Darwin had not the conception of unit 

 characters that is to say, independently heritable 

 characters which are handed on intact or dropped 

 out altogether in its modern clear-cut form, he 

 was well acquainted with mutations in domesticated 

 animals and cultivated plants, and he dismissed 

 most of them as not important. In the first place, 



