Ovulation in the Domestic Fowl 137 



and second ovulations, though this decreases as the number of members in 

 sequences increases from three to around seven or eight. But with this decrease 

 in lag between first and second ovulations with increasing sequence length, 

 there occur decreases in lag at subsequent positions, all of which become 

 fairly constant in sequences of seven or eight or more members. At sequence 

 lengths greater than seven or eight members, an increasing number of lag 



24 46 72 96(0) 24 



j4 



Ci \ ,-' Cz\ / CjA /' C|- \ ,' CzN 



Ol' 02' 



T 



Fig. 2. Time relationships in a 4-day cycle (« = 3). Hours of darkness (8.00 p.m.-6.00 a.m.) 

 are set off by the vertical stippled bands. The days of the cycle, top of the figure, are each 

 divided in an "open" period and a period of lapse, p and q respectively on the last day of 

 the cycle (hours 72-96). Subscripts denote successive events or members: R, onset of 

 OIH releases; C, follicles; O, ovulations; L, ovipositions; M, "maturation curves" of 

 the follicles. Q indicates the approximate hour of excitation and onset of OIH release if 

 the sequence were continued. Primed designations apply to the succeeding cycle. Other 

 details in text. (Based on Fraps (16, 17).) 



values approach or equal zero following decreasing order of lag in the first 

 several places. The interval between successive ovulations is then 24 hr. 

 Theoretically, at least, the number of members in a sequence may be increased 

 indefinitely with little or no increase in total lag beyond that seen in sequences 

 of some seven or eight members. It may be noted that lag always increases in 

 the terminal place or two before these lengthy sequences are terminated. 



In regularly ovulating hens, the termination of one ovulation sequence on 

 a given day is followed almost invariably by the initiation of another sequence 

 on the second day thereafter; ovulation fails to occur, that is, on only a single 

 day. This single day on which ovulation fails to occur may be denoted con- 

 veniently as the day of lapse. Unless otherwise stated, we shall be concerned 

 with the interim between the terminal ovulation of one sequence and the 

 initial ovulation of a succeeding sequence only in this limited sense. 



In Fig. 2, successive ovulations in a 3-member sequence are represented 

 by Ol, O2 and O3, the first and second ovulations of a succeeding sequence by 

 0( and Og. Lag of the second ovulation with respect to the first is indicated by 

 hOo, and of the third ovulation with respect to the second by hOg. Ovipositions 



