266 Biology in America 



Color Observed Expected 



Gray 24 27 



Black 8 9 



Yellow 16 9 



Sooty 2 9 



Blue-gray 8 3 



Blue ...2 3 



Cream 3 3 



Pale sooty 2 1 



Another cross between two grays of a different sort gave 

 the following results as compared with those to be expected : 



Color Observed Expected 



Gray 20 27 



Black .....8 9 



Yellow 12 9 



Sooty 1 3 



Blue-gray 7 9 



Blue 4 3 



Cream (?) 3 



Pale sooty 1 1 



White 8 21 



''The category yellow is probably too large because of a 

 failure on our part to discriminate between yellow and cream, 

 a difference which at first we failed to record. It is possible 

 also that albino young were not enumerated in all the rec- 

 ords which we have combined, and so albinos are apparently 

 deficient in number. ' ' 2 



What is the new science of genetics doing for the world in 

 a practical way? It is scarcely necessary to suggest that a 

 knowledge of inheritance is fundamental to the practice of 

 breeding animals and plants. But the new genetics is scarce 

 two decades old, while during the preceding centuries man 

 has produced the wonderful diversity in domesticated varie- 

 ties which we know today. Has all this earlier improvement 

 been due to chance alone? Is the scientific breeder a prod- 

 uct of the last twenty years? Hardly, for we are using 

 today the same principle of selection which has been the 

 magic wand of the breeder in the past. But to this prin- 

 ciple has been added more accurate knowledge of kinds of 

 variation and the laws of their inheritance, so that today the 

 breeder can work more surely and swiftly than his predeces- 

 sor in the past. 



2 Castle, ' ' Inheritance in Rabbits," Carnegie Institution, Publica- 

 tion No. 114, p. 59. 



