No. G31] COLOR CLASSES IN DOVES AND CANARIES 167 



Although the cross just considered is the one chiefly cited, it is 

 of interest to attempt to apply the three possibilities in question 

 to the reciprocal cross namely colored male X white female — 

 as follows : 



(a) If no non-disjunction; forms WFM CwFMand 

 gametes: }wFm 



(6) If non-disjunction in the male, WWFFMMand) (wFMand 

 forms gametes: \ )wFm 



(c) If non-disjunction in the female, WFM fwwFFMm and 



forms gametes: \ - 



(a) No non-disjunction. A normal mating of this type gives 

 two classes of offspring as follows : 



No exceptions have been recorded. 



(b) Non-disjunction in the male: would expect four types of 

 zygotes as follows : 



(1) WWn-FFFMMM =s colored males? Probably die. 



(2) WWwFFFMMm = colored males— transmitting non-disjunction. 



(4) wFM — = whites? Probably die. 



Bid class b(3), sterile white females occur, their appearance 

 would undoubtedly have been noted and recorded. It should 

 further be noted that non-disjunction, namely in the male, is the 

 only type able to account for the appearance of exceptional 

 colored females in the cross reciprocal to that just considered. 

 In this cross, however, this type of non-disjunction expects a 

 color class which has not been recorded in matings of supposedly 

 homozygous colored males. 



<c) Non-disjunction in the female: 



(2) WFM F — FMMm == colored females? Sterilef 



Here, non-disjunction gives no exceptions save the occurrence 

 of an occasional sterile colored female. This would undoubtedly 



