100 



GENETICS 



offspring are, in each instance, arranged under their 

 respective midparents. 



The mean group for all the midparents, it will be 

 seen, is 68.5, and the offspring of this group average 

 68.3. The table is expressed graphically in Figure 

 33 in which the circles connected by the diagonal 

 line represent the graded parental heights, while the 

 arrowpoints indicate the average heights of the off- 

 spring in each group. In order to compare these 

 two series of numbers more readily, they may be 

 reduced to a common basis in which the mean class 

 in each instance is made equal to 100, as follows : — 



The same series may be expressed in terms of 

 amount of deviation from the mean or middle classes, 

 as shown below. The deviation of each group in the 

 series is marked by the signs + or — according as 

 the heights given are greater or less than 100. 



