150 Heredity, 



marks that every one knows that the chief difficulty is 

 in breaking through tlie original form and color of the 

 species, and every one will be on the lookout for any 

 natural sport, either from seed .or branch; that being 

 once obtained, however trifling the change may be, the 

 result depends upon himself. M. de Jongbe, with ref- 

 erence to pears, says the more a type has entered into a 

 state of variation, the greater is its tendency to continue 

 doing so, and the more it is disposed to vary still fur- 

 ther. Vilniorin says that when any particular variation 

 is desired the first step is to get the plant to vary in any 

 manner whatever, and to go on selecting the most varia- 

 ble individuals, even though they vary in the wrong 

 direction; for the fixed character of the species once 

 broken, the desired variation will sooner or later ap- 

 pear. 



Darwin gives quite a list of authorities to show that 

 after English dogs have been bred for a few generations 

 in India they degenerate, not only in their mental facul- 

 ties, but in form. 



Accord ino^ to Bach man, turkevs reared from the eo-as of 

 wild ones lose their metallic tints and become spotted 

 with white in the third generation. 



It will be seen from the instances which have been 

 given that the number of generations which are exposed 

 to the new conditions before variation is induced varies 

 greatly. In the case given by Dr. Kirtland, fifty years 

 elapsed before variations of the red cherry began to ap- 

 pear. In the case last quoted, variation appeared in the 

 third generation, andYarrell says that Australian dingos 

 bred in the Zoological Gardens of England, almost in- 

 variably produced in the first generation puppies marked 

 with white and other colors. 



Sir Charles Lyell mentions that some Englishmen en- 



