Nos. 618-619] EGG PRODUCTION 



307 



time in February. Three hundred and ten days seems, 

 moreover, to mark the approximate boundary of a group 

 of stragglers which perhaps corresponds to Pearl's after 

 March 1 group of producers, i. e., his zero producers. 

 This group is represented in the curve by the shoulder 

 which begins at this point, there being of course an over- 

 lap with the larger group, beginning somewhere about 

 280-290 days. 



The relation of the abstract numbers involved in the 

 series of data relating to winter egg production is a mat- 

 ter of some importance. The mean of the abstract num- 

 bers from 1-30 is 15.5, or from 0-30, 15, a value that cor- 

 responds closely to the mean value of the number of eggs 

 laid by the under-thirty class. The mean value of the 

 numbers above 30 beginning at 31 and proceeding to some 

 other higher number such as 50 or 80, will depend in part 

 on the value chosen for the higher number. If 80 be 

 chosen as the higher limiting value, then the mean of the 

 numbers 31-80 is found to have a value of 56.2. The 

 mean values just given hold only when the abstract num- 

 bers are taken one at a time or when they are arranged 

 in a symmetrical fashion about the mean, as, for example, 

 in the ratio of 1:2:3:4, etc., and back to 4 : 3 : 2 : 1. If 

 the 1-30 winter egg production group represented a defi- 

 nite genotype one would expect a symmetrical or nearly 

 symmetrical distribution of the concrete numbers about 

 their mean. If, however, the numbers (abstract or con- 

 crete, as the case maybe) had some other sort of arrange- 

 ment—as, for example, if they formed part of a normal 

 curve of variation— a different set of mean values would 

 be obtained, depending upon the steepness of the slope 

 of the curve. If, for example, the classes 1-5, etc., to 25- 

 30 inclusive, are formed and the central values appear in 

 the ratio of 1:1.3:1.7:2:2.3:2.7, the mean will be 18.2. 

 On the other hand, the mean of the abstract numbers 

 above 30 that form the remainder of the normal curve, 

 under some circumstances may shift downwards, as, for 

 example, when the mode of the curve is at 50 with the 



