258 



Biology in America 



luodilird by oilier trails) in the make-up of the organism. 

 The basis of this persistence we liave already seen to bo the 

 chromosome. In those cases in which one character domi- 

 nates anotlier (tallness vs. dwarfness in peas, color vs. al- 

 binism in animals, etc.), we have the phenomenon known 

 as latency, in which the determiner of a character may be 

 passed along for several generations, without the character 

 itself coming to expression. In such cases the character is 

 definite and the individual is distinct in respect to its pos- 

 session. There is no uncertainty for example, as to whether 



InHEKITANCE of COLOIi IN THE FoUR O'CLOCK 



F], Fo, first and second generations. From Morgan, Stiirtcvtint, Mul- 

 ler and Bridges, "Mechanism of Mendclian Inheritance." 



By permission of J. B. Lippincott Company. 



a guinea pig is spotted or uniform in color, or a man's liair 

 is curly or straight. There are cases however in which the 

 organism is neither "fish, flesh, nor good red herring," or 

 speaking scientifically dominance is imperfect or incomplete. 

 The four o'clock (INlirabilis jalapa) has a white- and a red- 

 flowered race, which when crossed produce plants with pink 

 flowers. When these pink-fiowered plants however are bred 

 inter se they produce 1 red to 2 pink to 1 white offspring, 

 the firet and last classes of which breed true, while the mid- 

 dle class when inbred continues to "throw" red, white and 

 pink plants in the above ratio. A crude chemical analogy 

 to these phenomena may be made in the following way : At 



