BIOMETRICS 



151 



(the dark rays on top of the seed-capsule) in three groups 

 of poppies — in Nos. I. and II. for two wild poppies, in 

 No. III. for a greater number of poppies forming a local 

 race. The numbers of stigmatic bands are indicated on 

 the base line. We have the following modes and means of 



the three curves respectively : 



Mode. Mean. 



No. 1 8 .. 8-50 



„ II. .. .. II .. 107s 



,, III. . . . . 10 . . 9*84 



We see that the race has a mode different from either of 

 the individual poppies, and also a different mean. 



In a symmetrical curve — and wc shall in the following 

 deal only with symmetrical curves — the mode and mean 

 fall together : in curve III. this is nearly so, there being a 

 very slight difference between the mode and the mean. 



Q Q M 

 Fig. 69. — Curves of Probability. (After Lotsy.) 



But all this is not yet sufficient. What we want is to be 

 able to compare the variability of one set of varying 

 characters with another set. In other words, we have to 



