124 MAINE AGRICULTURAL EXPERIMENT STATION. 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 1 to 3 usually 
two eggs separated by one or two 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, 1911. 
