SELECTION WITHIN PURE LINES OF PESTALOZZIA 



161 



The means of the different generations of the plus and minus lines are 

 plotted in figure 5 and show variations comparable to those shown in 

 figure 2. If an effect of selection had been secured the means must neces- 

 sarily have shown increasing deviation one from another throughout the 

 experiment. Such increases as they have shown have been compensated 

 by corresponding decreases so that it becomes evident as the experiment 

 is carried on for a considerable period that these increases and decreases 

 of the deviation between the two selections are only the result of the chance 

 fluctuations which take place within the two lines. It is probable that such 



TABLE 4 



Mean spore lengths of generations of experiment 1. Each mean was computed from the means 

 of the cultures in its group for that generation. Each mean, except in the intermediate group is 

 accordingly based on approximately 1000 individual measurements. Values are given in fi. 



Difference between plus-selected line and minus-selected line = 0.105 + 0.068. 

 Difference between plus-selected line and intermediate line = 0.18 + 0.104. 

 Difference between minus-selected line and intermediate line =0.07 +0.097. 



differences would occur between any two separate lines, descended from 

 the same parent but cultivated separately. 



The means of each of the generations in the plus-selected line, the minus- 

 selected line, and the unselected intermediate group, and also the mean 

 of means of all cultures in each of these lines for the whole experiment are 

 shown in table 4, while table 12 (in the appendix) gives the means of all 

 cultures measured in this experiment. The differences between the lines 

 are in themselves very small and when compared with their probable 

 errors they are seen to be insignificant. However, had the experiment 



GENETICS 7: Mr 1922 



