INHERITANCE OF FECUNDITY 161 



deemed best to take the whole flock of Barred Rock pullets for 

 the laying year 1910-11, without any selection. The comparison 

 is sufficiently striking even on this basis. 

 From tables 1 and 2 it will be noted that: 



1. The mean winter production of the Cornish Indian Games 

 is less than one-third that of the general flock of Barred Plymouth 

 Rocks, under uniform environmental conditions. 



2. The winter production of the Games is considerably less 

 than a fourth of that of the high producing lines of the Barred 

 Rocks. 



3. The variabilities in both cases are high, but relatively not 

 significantly different. It is of interest to note that the observed 

 coefficients of variation for winter production here given are of 

 the same order of magnitude as the mean coefficients for the lay- 

 ing of the four winter months, November, December, January 

 and February. Taking the mean of the coefficients of variation 

 for these four months as given by Pearl and Surface (37, table 5, 

 p. 96) we get 95.15. 



The inferiority in egg production of the Cornish Indian Games 

 is most strikingly shown by the integral curves from table 1. 

 In table 3 the integral curves are given (in inversed form) for the 

 winter production of Barred Rock and Cornish fowls. 



The data of table 3 are shown graphically in figure 2. 



This diagram is to be read in the following manner. The 

 percentages of the flock laying a specified number of eggs are 

 plotted on the abscissal axis. The different egg productions are 

 plotted as ordinates. From the diagram it appears (for example) 

 that whereas 47 out of every 100 birds in the Barred Rock flock 

 each produced 35 or more eggs in the winter period, only 4 and a 

 fraction birds out of every 100 in the Cornish Indian Game flock 

 were able to produce as many eggs as this — 35 — in the same period. 



Now in individuals which are high layers, and have this charac- 

 teristic in hereditary form, there must be involved some further 

 physiological factor in addition to the normal ovulation factor 

 already discussed. An analysis of extensive statistics has shown 

 (36, 37) that high fecundity represents essentially an addition of 

 two definite seasonal, laying cycles to the basic, normal reproduc- 



