254 GENETICS IN RELATION TO AGRICULTURE 
The above analysis not only demonstrates that Johannsen’s material 
was a mixture of different ‘weight types”’ but it also gives striking proof 
that selection within a single pure line has no effect. Johannsen points 
out that in certain lines ([, X, XJ) there seems to be a slight effect but 
that in others (VI, 1X, XII, etc.,) an opposite tendency appears; while 
still others (IZ, III, VIII) are irregular. Generally speaking then no 
effect of selection is seen for there is no significant difference between the 
means of the several groups in each pure line. The apparent indications 
of selection effects are merely fortuitous variations. In each of these 
lines, therefore, the offspring of plus and minus variants exhibit complete 
regression to the mean of the particular line. In short, individual varia- 
tions were not inherited, only the characteristic modifiability of the particu- 
lar line was inherited. 
Johannsen did not rest here but continued to test his pure lines of 
beans during successive years. He found a certain amount of seasonal 
fluctuation in the range of variation and in the variation constants, yet 
each pure line maintained its own individuality as indicated by the varia- 
tion in weight of beans produced. And this maintenance of entity was 
accomplished in spite of repeated selections of smallest and largest beans 
so that each year every pure line was represented by two lots of plants, a 
‘plus strain’’ grown from the largest beans and a ‘“‘minus strain” grown 
from the smallest beans. Complete failure of such repeated selection to 
cause significant change in the mean weight of either strain was observed 
in each pure line. As illustrations the data on Lines I and XIX are 
presented in Tables XLII and XLIII. 
From these data it is evident that six years of selection of plus and 
minus strains within Line I produced no permanent departure in either 
direction. In fact the last column (B—A) actually shows an inverse effect 
during three of the six years. Moreover, if the average of the means for 
the six years in both strains be compared this conclusion is verified. 
TaBLeE XLIJ.—SeELEcTION-EFFECT DurRING Six GENERATIONS IN LINE I oF THE 
Princess Beans. (From Johannsen) 
Mean weight of Mean weight of progeny seeds of 
tal | mother beans of “ 
Harvest neces the select strains | Differ- So eta Difference 
years of Ae B-A 
| beans g 
| a—minus | b—-plus A-minus B-plus 
1902 145 60 70 10 | 63.15+1.02 | 64.8540.76 | +1.70+1.27 
1903 252 55 80 25 | 75.19+1.01 | 70.88+0.89 | —4.3141.35 
1904 711 50 87 37 | 54.59+40.44 | 56.68+0.36 | +2.09+0.57 
1905 654 43 73 40 | 63.55+40.56 | 63.6440.41 | +0.09+0.69 
1906 384 46 84 38 | 74.38+0.81 | 73.0040.72 | —1.38+1.08 
1907 379 56 81 25 | 69.07+0.79 | 67.66+0.75 | —1.41+41.09 
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