70 



LINKAGE 



ing over between the sex factor and the various sex 

 Unked factors can not be calculated, since in the sex 

 that is heterozygous for the sex factor no crossing 

 over has been observed. Sex linkage has been found 



Fs 



Fig. 26. — Black Langshan female by Barred Plymouth Rock male. 

 Compare with Fig. 30 (similar cross in Abraxas) for scheme of inheritance, 

 which is the same in both. Substitute Black for lacticolor and Bar for 

 grossulariata. 



in the moths Abraxas (Figs. 30 and 31) and Lyman- 

 tria, in the fowl (Figs. 26, 27, 28, 29) (six factors), 

 canary, pigeon, Drosophila (Figs. 9 and 10), fish, cat, 

 man, and the plant Lychnis. In all, somewhat more 

 than fifteen species show linkage. 



This number appears small in comparison with the 



