CONTROL OF ANNUAL GONADAL CYCLES 



721 



logW 



time 



Fig. L Combined testicular weights (W) of first-year Zonotrichia 

 leucophrys gambelii as a function of time with constant daily photo- 

 periods of stimulatory duration. Time is in arbitrary units. Closed circles 

 represent developing testes; open circles represent regressing testes. (From 

 Farner and Wilson, 1957b.) 



approximates a linear function of p. The nature of the relationship 

 between k and p for values of p less than about 9.5 hr is uncertain. 

 When p = S, k must be very close to zero; however, the normal varia- 

 tion in resting testicular weights makes an exact evaluation impossible. 

 It must be remembered, however, that k is a. logarithmic rate constant 

 and consequently that daily testicular growth increments for values of 



