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POPULAR SCIENCE MONTHLY. 



from ears with many rows, and that the greater the number of 

 rows on the ear from which the seed is taken the smaller is the 

 number of ears produced with a small number of rows. It is 

 also plain that, as the number of rows on the ear from which the 

 seed was taken increases, the number of ears produced with a 

 large number of rows increases, and that we have in each case a 

 very considerable number of ears which equal their parents and 

 a few which excel them, even when the parent seeds are far be- 

 yond the maximum for all ordinary corn. Fritz Miiller says he 

 has never, under ordinary conditions, except in three instances, 

 found an ear with more than eighteen rows, and Darwin puts the 

 maximum at twenty rows ; yet we have among the children of 

 seed from a twenty-two-rowed ear no less than 4*8 per cent, or 

 eighteen ears out of 373 with twenty rows, and one ear out of 373 

 with twenty-six rows, and it will also be seen that the number 

 of children which equal their parents increases in each case in 

 each successive generation. 



Thus the seed planted in 1867 from an eighteen-rowed ear 

 produced 12*6 per cent of eighteen-rowed children. The eighteen- 

 rowed ear planted in 1868 from an eighteen-rowed parent pro- 

 duced 18*2 per cent of eighteen-rowed children, and the eighteen- 

 rowed seed planted in 1869 from eighteen-rowed parents and 

 grandparents produced 18'6 per cent of eighteen-rowed children. 

 The series is 12'6 per cent, 18'2 per cent, and 18*6 per cent. 



The rapid change which took place in the " type " after only 

 three years of selection is well shown by the following table, 

 which gives the dominant number of rows at each sowing, and 

 also the percentage of ears which had this number : 



1867, 12 rows 48 per cent. 



1867, 14 " 48-6 " 



1868, 14 " 48-5 " 



1867, 14 " 37-8 " 



1868, 14 rows 36 -4 per cent. 



1869, 14 " 37-3 " 



1869, 16 " 41-6 " 



1869, 16 " 41-8 " 



The minimum for the third generation is equal to the mean 

 for the first ; the mean for the third generation, sixteen rows, is 

 very near the maximum for ordinary corn, and the maximum for 

 the third generation is far beyond the maximum for the grand- 

 parents, and much beyond the maximum for the parents. 



No one can dispute the well-known fact that this sort of pedi- 

 gree selection for a single point quickly grows less and less 

 effective, and soon reaches a maximum ; but this is no proof of 

 any " principle of organic stability," or anything else except the 

 truth that long ages of natural selection have made the organism 

 such a unit or co-ordinated whole that no great and continuous 

 change in one feature is possible, unless it is accompanied by 

 general or constitutional change. 



