318 ILLINOIS ACADEMY OF SCIENCE 
der more constant conditions. Let us apply them to these 20 
generations of isolation 11. We find the 20 parents fall into 
eight classes or groups which we made before for the parents 
of the three sublines. The number of these parents in these 
different classes, their lengths, and the means of the offspring 
of the parents belonging to each class are given in the follow- 
ing table: 
If we make a plot to show the position of these parent 
classes and the means of the offspring in relation to the mean 
of the line, we get the following graph: 
2.05 
2.00} 
195 
1.70 
1.85 
1.80 
ig 
1.70 
1.05 
1.60 
1.557 
1.45 
1.40 
1:35 
GRAPH THE SAME AS FOR FIGURE 1. 
If we examine this diagram we notice that if the dotted 
line joining the arrowheads (which we may call the line of 
