Case 



III. Cornish Indian Game (male) x Barred 

 Plymouth Rock (female). 



bW bW = male gametes 



BW 



Female 

 Gametes 



Case IV. Fi Barred {male) x Fi Unbarred {female) of 

 Case III. 



BW 



bW 



= male gametes 



Female 

 Gametes 



bW 



i.e. 50% barred, 50% unbarred. 

 (See Fig. 19). 



Morgan says that the results of such crossing "means 

 that the Barred Plymouth Rock is a black race with an 

 additional dominant factor for barring. The Black Lang- 

 shan is the same black race but without the barring factor." 



Egg Production in Fowls 



The inheritance of egg-production or fecundity has 

 been shown by Dr. Pearl to be sex-linked. As the subject 

 is too intricate for full discussion in a work of this kind 

 reference will be made only to the main features. 



Pearl found (a) that high egg-production could not be 

 obtained by selecting good-laying hens only as mothers; 

 and (b) that the laying capacity of hens could be ascertain- 

 ed at an early stage by noting the first winter production. 

 On this basis he classifies hens into three groups : ( 1 ) those 

 laying over thirty eggs during their first winter will lay from 

 150-200 eggs during the year, (2) those laying fewer than 

 thirty eggs during the winter will lay from 80- 1 20 eggs, and 

 (3) those laying no eggs will lay from 40-60 eggs. 



With the above groups in mind Pearl advanced the 

 working hypothesis that the egg-laying capacity of hens 



118 



