[ 369 i 



XXX. 



AN EXAMPLE OF THE MULTIPLE COUPLING OF 

 MENDELIAN FACTORS. 



By JAMES WILSON, M.A., B.Sc, 

 Professor of Agriculture in the Royal College of Science, Dublin. 



[Head December 15, 1914. Published Januahy 8, 1915.] 



The history of the English Campine varieties of fowl, as told in two 

 pamphlets, " The Campine " and " The Production of the English Type Gold 

 Campiue," by the Ilev. E. Lewis Jones, reveals the coupling of more than 

 two factors in the presence of uncoupled factors having effects similar to 

 those of the coupled factors. 



Multiple coupling was revealed in the Cambridge experiments with sweet 

 peas. Two varieties, Duke of Westminster and Painted Lady, whose flowers 

 differed from each other in three pairs of characters, were mated, and, in the 

 progeny of their hybrids there were only three groups instead of eight, as 

 there should have been, had there been no coupling. 



Multiple coupling is undoubtedly common, and is very obvious in regard to 

 sex, since many characters invariably follow either the one sex or the other. 



In the Campine fowl the factor for femaleness is coupled with two other 

 factors at least ; but, because of the presence of uncoupled factors having 

 similar effects, the same sex is not always followed by the same characters. 



A well known case of a similar nature, but in which only two factors are 

 coupled, might be quoted by way of introduction. 



It has already been shown that in fowl the males are pure as regards the 

 factors for sex, while the females are hybrid. The two sexes may therefore be 

 represented factorially as — 



Male. Female. 



MM M F 



When pure barred males are mated with plain feathered females the progeny 

 are all barred : from which it can be inferred that barring is dominant to 

 plainness. On the other hand, when pure bred barred females are mated 

 with plain males, only half the progeny are barred, while the other half are 



SCIENT. PEOC. E.D.S., VOL. XIV., NO. XXX - 3 O 



