124 MAIXE AGRICULTURAL EXPERIMENT STA.TION. I914. 



when a bird was broody the first year she was also broody the 

 second year and if she was not broody the first year she did 

 not show this instinct the second year. Typically a bird which 

 was broody at all was broody four or five times during a season 

 but the number of times varied from i to 7 with the indi- 

 vidual. The nine birds which were never broody show all de- 

 grees of a tendency to lay in litters from zero in the extreme 

 case of one bird which laid from February to the end of the 

 year at a nearly uniform rate, i. e., in clutches of i to 3 usually 

 two eggs separated by one or t\vo days on which no egg was 

 laid, to the opposite extreme of a bird which had exactly the 

 same definite periods of non-production as the birds with typi- 

 cal broody periods but she lacked the instinct to incubate the 

 eggs. 



4. Within a litter the laying is broken up into clutches. The 

 eggs of a clutch are laid on successive days. The clutches ire 

 separated by one or two (occasionally more) days on which no 

 eggs are produced. 



5. The number of eggs in a clutch and the number of days 

 between clutches vary in the different birds in the same season 

 and in the same bird at different seasons. During the part 

 of the year when the bird is not laying in litters succeeded by 

 broody periods the size of the clutches is small. The birds 

 which lay continuously (i. e., do not lay in litters) lay in small 

 clutches throughout the season. During the part of the year 

 when periods of production alternate with periods of broodiness 

 the litters show a decided tendency to start and end with small 

 clutches while the number of eggs in the intermediate clutches 

 is larger. An individual may nevertheless start or end a litter 

 with large clutches. 



These facts, in general, accord with the hypothesis of Pearl 

 and Surface.* "The actual visible egg production in each in- 

 dividual bird tends to occur in definite cycles or periods of 

 varying lengths, alternating with non-productive periods." 



"The rate of fecundity (amount of egg production per unit 

 of time conceived in the sense of the differential calculus) is 

 in any bird a minimum at the beginning of the cycle of produc- 



* Pearl, R. and Surface, F. :M. A Biometrical Study of Egg Pro- 

 duction in the Domestic Fowl. II. Seasonal Distribution of Egg Pro- 

 duction. U. S. Dept. of Agr., Bui. An. Ind. Bui. no, Pt. II, 191 1. 



