292 MAINK AGRICULTURAL EXPERIMENT STATION. I912. 



TABI.E 3 



Showing the percentage of the zvhole flock producing in the winter 

 period more than certain specified numbers of eggs, in the case (a) 

 of Barred Plymouth Rocks and (h) of Cornish Indian Games 



The Indicated Percentage of the Flock 

 Produces in the Winter Period 



6 or more eggs 



12 or more eggs 



18 or more eggs 



24 or more eggs 



30 or more eggs 



36 or more eggs 



42 or more eggs 



48 or more eggs 



54 or more eggs 



60 or more eggs 



66 or more eggs 



72 or more eggs 



78 or more eggs 



84 or more eggs 



90 or more eggs 



96 or more eggs 



102 or more eggs 



108 or more eggs 



114 or more eggs. 



120 or more eggs , 



Cornish Indian. 

 Game 



mal reproduction cycle. These added periods of productivity 

 are what may be called (cf. 37, 28, 30) the winter cycle and 

 the summer cycle. The winter cycle is the more important of 

 these. It is the best practical measure of relative fecundity 

 which we have and has been used as the chief unit of fecundity 

 in these studies. It constitutes a distinct and definite entity in 

 fecundity curves. The existence of this added fecundity, in 

 high laying- birds must depend upon some additional physiolog- 

 ical factor or mechanism besides that which suffices for the 

 normal reproductive tgg production. Given the basic anatomi- 

 cal and physiological factors the bird only lays a large number 

 of eggs if an additional factor is present. 



As to the nature of this physiological mechanism we can only 

 speculate. It probably involves fundamentally such matters as 



