CHAPTER VIII 



MENDELISM (continued) 



MENDEL'S law, as stated in the preceding chapter, 

 has already been found to hold good in a very large 

 number of cases cases in which all kinds of characters 

 are concerned, belonging to many different species of 

 animals and plants. In certain instances, however, 

 complications arise, and these may be treated of in 

 two main sections. 



The first kind of complication arises from the pheno- 

 menon known as coupling. The essence of this pheno- 

 menon consists in the existence of some kind of affinity 

 occurring in the same individual between allelomorphs 

 which belong to distinct pairs. In consequence of such 

 an affinity exceptions are found to the rule that sepa- 

 rate pairs of allelomorphs segregate independently. 



The closeness of the connection between the char- 

 acters concerned shows a series of gradations in dif- 

 ferent cases. In the simplest cases of all, what are 

 loosely spoken of as separate characters are found on 

 closer examination to be only different aspects of one 

 and the same characteristic feature. These cases, then, 

 offer no real exception to the rule, for only one pair of 

 allelomorphs is actually concerned. As an example, we 

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