78 THEORY OF EVOLUTION 



In the reciprocal cross (fig. 40) black cock 

 by barred hen, the daughters are black and the 

 sons barred criss-cross inheritance. These 



FIG. 39. Sex-linked inheritance in domesticated birds shown 

 here in a cross between barred Plymouth Rock male and black 

 Langshan female. 



inbred give black hens and black cocks, barred 

 hens and barred cocks. 



There is a case comparable to this found in 

 a wild species of moth, Abraxas grossulariata. 

 A wild variation of this type is lighter in color 



