338 



The Ohio Naturalist 



[Vol. V, No. 7, 



crossed it frequent!}^ occurs that the resulting hybrids exhibit 

 the character from one parent onty. The character which 

 appears is said to be dominant while the corresponding character 

 from the other parent not in evidence is called recessive. But if 

 these hybrids are bred among themselves they give rise to 

 offspring of two t^^pes, some showing the dominant character and 

 some the recessive, and these usually appear in the proportion of 

 3:1. By further trial it is found that about one-third of the 

 dominant individuals are pure and two-thirds of mixed nature. 



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yell oar 



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Fig. 4. Diagram showing the operation of Mendel's law with peas having 



yellow and green cotyledons. 



These latter will again produce offspring of both types the same 

 as the original hybrids, and so on for many generations. The 

 first instance discovered by Mendel related to the color of the 

 cotyledons in peas. The yellow color of cotyledons was found to 

 be dominant over green. The operation of Mendel's law as 

 regards the yellow and green colors of cotyledons is shown in 

 Fig. 4. Albinism among animals also furnishes a familiar exam- 

 ple of the operation of Mendel's law. If albino mice are mated 

 with gray mice the offspring are gray, but in the following gen- 

 eration one-fourth will again be albinoes. The gray is the dom- 

 inant and the albino the recessive character. 



