THE PURE LINE AND SELECTION 139 



was able to isolate eight races, or pure lines, whose 

 average size, drawn to scale, is shown in Figure 28. 



Each of these pure lines produced a progeny which 

 exhibited a considerable range of fluctuating variation. 

 The offspring of pure line D, for example, varied from 

 256 to 80 micra x in length with an average of 176 

 micra, as shown in Figure 29, where samples of the 

 different classes of variants in pure line D are arranged 

 in a series. 



256 < 



Micra 



- 80 



FIG. 29. Diagram of a single race (D) showing the variation in 

 the size of the individuals. Magnified about 230 diameters. 

 After Jennings. 



A single representative of each of the different classes 

 of variants out of all the eight pure lines bred by 

 Jennings is shown in Figure 30. 



Each horizontal row represents a single race or 

 pure .line, the average size of which is indicated by the 

 sign +. The mean length of the entire lot, as shown 

 by the vertical line, is 155 micra. The total number 

 of individuals belonging to each size is not indicated, but 

 1 A micron is 1-1 000th of a millimeter. 



