Mendelism 



259 



ordinary temperatures chromic sulphate forms a violet-col- 

 ored solution in water, but at lower temperatures the salt 

 crystallizes out leaving the water colorless as before. A con- 

 centrated solution, deep violet in color, may be taken to rep- 

 resent the color of the red-flowered four o'clock, while water 

 may represent the color of the white-flowered variety. By 

 mixing the concentrated solution and water in equal quanti- 

 ties, a solution of light violet color is obtained, which may 

 represent the pink-flowered hybrids of the first generation. 

 If this dilute solution be now divided into four equal parts, 



INHERITANCE IN ANDALUSIAN FOWL 



PI, parents; F a and F 2 , the first and second generation offspring of 

 the cross. From Morgan, "The Physical Basis of Heredity." 



By permission of J. B. Lippincott Company. 



to one of which a sufficient volume of salt be added to restore 

 the original color, while two are left unchanged and the fourth 

 is cooled, thereby separating. the salt from the water and leav- 

 ing the latter colorless, a superficial analogy to the phenom- 

 ena of color inheritance in the four o 'clock is obtained. I say 

 "superficial" or "crude" analogy, because the physical proc- 

 ess outlined above is far too simple to represent the compli- 

 cated bio-chemical processes involved in that of inheritance. 



One of the best known cases of imperfect dominance is that 

 shown by Andalusian fowls, although as we shall see this 

 case is not strictly comparable to the preceding. The "blue" 

 Andalusian is a chicken in which black is mixed with white 



