ALTERNATIVE EXPLANATIONS FOR EXCEPTIONAL 

 COLOR CLASSES IN DOVES AND CANARIES 



DR. C. C. LITTLE 



Carnegie Institution of Washington 



Doves and canaries have been shown to possess certain color 

 factors which are sex-linked in inheritance. The behavior of 

 these factors leads one to the conclusion that, unlike DrosophUa, 

 cats and man, the female and not the male is the homozygous sex. 

 In this respect they resemble Abraxas, poultry and the domestic 

 pigeon. 



In both doves and canaries, however, there occur exceptional 

 color classes in certain matings where the sex-linkage of the 

 factors in question manifests itself. To explain the appearance 

 of these exceptional color classes, Sturtevant (1912) (in canaries) 

 and Bridges (1913) (in doves) have suggested that the principle 

 of partial sex-linkage is involved. 



Later, Bridges (1916), in discussing the phenomena of non- 

 disjunction in DrosophUa, has reviewed briefly other forms to 

 which he considers non-disjunction may apply and among these 

 mentions doves and canaries as follows : 



(Doves— p. 157) Exceptions to the inheritance of blond and the dark 

 types of pigeons have heen explained as partial sex-linkasjo ( Bridge?, 



plausible. 



(Canaries— p. 158) Exceptions to sex-linkage in the inheritance of 

 pink versus black eye colors have been reported (Durham and Many;,! 1 . 

 1908). These exceptions are explainable by non-disjunction or by par- 



In this pape*r an attempt will be made to show that the hypoth- 

 esis of partial sex-linkage and of non-disjunction expect certain 

 results from the crosses made, which have not been reported and 

 in the case of non-disjunction might, in addition, be fairly con- 

 sidered as involving sterility of certain color classes — a phenom- 

 enon not yet reported in any of the forms in question. 



A further effort will be made to explain the observed facts on 

 an hypothesis of factorial change which involves neither a break 

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