66 THE CALL OF THE HEN. 
14 of an inch behind the forefinger. If this hen is mated to a male 
bird of the same type and prepotency, her eggs will be very fertile, and 
a large number of the progeny will be equal to and some will excel the 
parent stock in the lines that predominate in the parents. By selecting 
these few specimens each season for breeding, it is possible to breed a 
highly valuable type in the course of time. Fig. 43 shows how to hold 
a bird between the knees after you become proficient in testing the head 
while the bird is in a sack. After a little practice you will become so 
proficient that you can test birds for prepotency without having to put 
them in a sack. 
Fic. 41—Showing thumb '/, of an inch behind forefinger; indicating hen has pre- 
potency full. (See Skull No. 2, Fig. 35.) 
CHAPTER X. 
TESTING HENS ON A LARGE SCALE, USING CHartTs 44 AND 45. 
I will describe in this chapter how I cull hens when we have large 
numbers of them, as we have in poultry plants in California. I shall 
