PURE LINES 251 
These two series may be expressed in terms of percentage by multiplying 
each series by a factor that will change the value of the middle class to 
100. The mean weight of all the mother beans was very nearly 50 cg. 
while that of the progeny is approximately 40 cg. Thus the first series 
is multiplied by 2 and the second by 2.5 giving the following result. 
| 
Weight of mother beans.......... | 60 | 80 | 100 | 120 | 140 | 160 
Mean weight of progeny........... | 93 | 97 | 100 | 108 | 11 | 14 
Now the deviation of each progeny class can be compared directly with 
the deviation of the mother class. 
| | 
Deviation of mother beans............. | —40 | —20 | Oo | 20 | 40 | 60 
| 
y 
Deviation of mean weights of progeny. i aed 
alo |e | n | us 
Thus the ratios of the minus deviations of the progeny classes to the 
minus deviations of the mother classes are 749 and 349, the mean of which 
is 13¢9 or 0.163. Similarly for the plus deviations, 849, 1149, 1460 x 4, 
0.303. The average of these two values is 0.233 which is about 14 as 
compared with Galton’s observation of 24 inheritance in size of seed in 
the sweet pea and stature in man. 
During these preliminary experiments, however, Johannsen noticed 
that plants grown from similar sized beans produced beans of very differ- 
ent sizes. Thus, for example, the plants grown from the largest mother 
beans (about 80 cg. in weight) yielded seeds of strikingly different sizes. 
The average weight of the seeds of these individual plants varied between 
35 and 60 cg. and when the weights of all the individual beans of this 
series were arranged in a frequency distribution it produced a series that 
differed considerably from the normal frequency distribution. The 
distribution of 598 seeds, all progeny of beans about 80 cg. in weight, 
when arranged in classes of 5-cg. intervals, was as follows: 
Classes.................-... 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 
Number of seeds............ 5 18 46 144 127 70 70 63 2815 8 4 
Theoretical numbers........... 1 3 11 26 53 85 109 112 91 59 3013 4 1 
| M = 45.44 + 0.43 cg.3 « = 10.40 cg. 
Clearly this distribution if plotted would produce a skew polygon with the 
mode to the left of the theoretical mode. This observation caused 
Johannsen to have serious doubt regarding the biological justification of 
Galton’slaw. For such a distribution did not appear to be the expression 
of only one “type”; on the contrary, it seemed more likely that the 
material was mixed. 
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