272 



RAYMOND PEARL 



2. Recurrence of brooding instinct with different degrees of 

 intensity in the same hen. 



3. Occurrence of brooding instinct outside of the breeding or 

 mating season. 



4. Broodiness not preceded by egg laying, or by very little 

 egg laying. 



5. The brooding instinct manifested with a very slight degree 

 of intensity. 



It should be said that all records of broodiness are exhibited 

 in the form of tables giving the daily egg records of the birds. 

 A single vertical stroke in the space corresponding to any given 

 date signifies that on that date the bird which is the subject of 

 the record laid an egg, while a blank space denotes the confine- 

 ment of the bird on that date because she showed the character- 

 istic symptoms of broodiness. An " O " signifies that the bird 

 was released from confinement " cured " on the date indicated. 



BROODINESS AS A CYCLICAL INSTINCT 



It has been pointed out above that the normal course of events 

 respecting broodiness in domesticated poultry is to be regarded 

 as a sequence of egg-laying periods and periods of brooding. 

 Table 1 embodies a record showing in a very clear and somewhat 

 extreme form the instinct of brooding occurring in this cyclical 

 fashion. 



Figure 1. Egg record of bird No. 139. 



From this figure it is seen that in bird No. 139 the first appear- 

 ance of broodiness was on March 24, following the laying of 19 

 eggs. On the eleventh day following — seven of these days 

 having been spent in the detention coop — she began laying 

 again. After laying 12 eggs she became broody again on April 



