284 MAINE AGRICULTURAL EXPERIMENT STATION. I914 



1 =z an tgg produced, 



and 2 denotes summation between the indicated limits 



we have 



^^Pn— 10 ■ ^ 



Rp =1 100 



21 



The rates so calculated for each successive day may be 

 plotted as a curve. 



Applying this method to records of one, two and three year 

 old hens many interesting and novel points regarding ovarian 

 activity, as expressed in ovulation, may be made out. The 

 long period secular cycles of production appear much more 

 clearly and precisely than in flock mass statistics. The steady 

 diminution in maximum rate of fecundity per unit of time 

 after the first spring cycle in the bird's life is very strikingly 

 shown in the great majority of cases. 



Studies on the Physiology oe Reproduction in the Domes- 

 tic Fowl. vii. Data Regarding the Brooding 

 Instinct in Relation to Egg Production.* 



This paper presents data regarding variations in the manifes- 

 tations of the brooding instinct in fowls. It is shown that: 



1. Broodiness normally constitutes one element in the cy- 

 clical reproductive activities of the female. It recurs with 

 greater or less regularity following periods of laying. 



2. The degree of intensity of the brooding instinct, both 

 in respect of its objective manifestations and in respect of its 

 physiological basis, may vary considerably at different times 

 in the life of the same individual. 



3. Broodiness in the domestic fowl is not necessarily con- 

 nected with any particular season. It may occur entirely out- 

 side the regular breeding season. 



4. While ordinarily broodiness is preceded by the laying of 

 a "clutch" of eggs, this need not necessarily be so. Cases 

 are cited in which well marked broodiness occurs without ante- 

 cedent laying. 



*This is an abstract of a paper bearing the same title by Raymond 

 Pearl published in the Journal of Animal Behavior, Vol. 4, pp. 266-188. 



