CORRELATED VARIATIONS. 83 



their marriage rate is so much higher. This increased 

 fertility is somewhat counteracted by their greater 

 death rate, but it would nevertheless appear that the 

 population will ultimately reproduce itself from the 

 artisan classes. 



Definite evidence of evolution under natural condi- 

 tions as the result of genetic selection has not been ob- 

 tained, but this may be simply because it has never 

 occurred to anybody to look for it. Professor Pear- 

 son * has, however, shown the existence of a highly 

 interesting and important relationship between fer- 

 tility and morphological characters in certain plants. 

 He counted the number of stigmatic bands on the 4443 

 seed-capsules obtained from 176 Shirley poppies grow- 

 ing in a single garden, and found the following fre- 

 quencies : 



Bands, 5678 9 10 11 12 13 14 15 16 17 18 19 



Frequency, 1 11 32 56 148 363 628 925 954 709 397 155 51 12 1 



Here we see that the 12 and 13 band forms were the 

 most common, the 11 and 14 ones less so, the 10 and 15 

 still less, and so on. To his surprise^ Professor Pear- 

 son found that whilst the commonest or type capsules 

 contained a very large number of seeds, the 11 and 14 

 band forms contained distinctly less, and the 10 and 15 

 ones very few seeds indeed, whilst the capsules with 

 very few or very many bands contained practically no 

 seeds. A repetition of these observations on the wild 

 poppy gave a very similar result, and this was likewise 

 the case with the seed capsules of" a number of plants 

 of Nigella Hispanica. The distribution of the seg- 

 mentation on 3212 capsules was as follows: 

 * " Grammar of Science," Ed. ii. p. 443. 



