COUPLING 



101 



Cocks 



Hens 



MM 

 XX 



MM 

 Xx 



MM 



XX 



M 

 X 



M 



X 



But since there are three grades of hens, there must be 

 more than one pair of factors. 



The first suggestion occurring is that there are three 

 free factors which are polygamous, and, if we call the 

 new factor Y, without questioning whether it be domi- 

 nant or recessive to X, there should then be three 

 different kinds of hens, and, from the reproductive 

 point of view, six different kinds of cocks, namely : 



Hens 



But, though there are just the three grades of hens, 

 there are certainly more than six kinds of cocks, as 

 can be told by the different assemblages of progeny 

 they produce. Thus there must be more than three 

 factors. 



A glance at the figures of production for the middle- 

 grade hens at the Munster Institute suggests another 

 theory. It will be noticed that the middle-grade hens 

 may possibly be of two kinds : those that begin to lay 



