PAPERS ON ZOOLOGY AND PHYSIOLOGY 311 
In the work with Aphis avenae, a special attempt was made 
to test the effectiveness of selection on body length, which 
corresponds to stature in upright animals. The chief reasons 
for this were that body length was well known to be affected 
by selection in higher animals that reproduce sexually, and 
because body length is a character easily and accurately meas- 
ured, In three different isolations selections were made in an 
attempt to increase the size or body length in the pure line. 
This was done by picking out the longest individual of each 
fraternity as the parent for the succeeding fraternity (next 
generation) in that isolation or subline. In isolation 5, se- 
lection was begun in the 26th generation, and continued for 
seven generations; in isolation I, selection was begun in the 
second generation, and continued for five generations; in 
isolation 11 selections were begun in the 43rd generation and 
continued for forty-four generations. This last series of se- 
lections is, I believe, about as long a series as has been obtained 
in any pure line work and gives us the rigid test so often sug- 
gested by pure line critics. In my previous paper (Ewing, 
1916), it was shown that in all three of these selection tests no 
shifting of the fraternal mean in regard to size had been de- 
tected. But critics may insist that if a careful statistical study 
bad been made a shifting might have been detected. In order 
to find out if such is the case, the following statistical studies 
are submitted in regard to selection, correlation and regres- 
sion in the case of these three isolations, or sublines, where se- 
lections were made in an attempt to increase the size of the 
individuals. 
In isolations 5, I and 11 we find 55 parent individuals in- 
cluded, which gave 542 measured adult offspring. Let us now 
place these 55 parent individuals in different classes accord- 
ing to their length. We get the following arrangement: 
Lengths in mm. _|1.25-1.29|1.30-1.34]1.35-1.39]1.40-1.44] 1.45-1.49|1,50-1.54| 
SESE ST RE a A ed a ee PE), 
1.55-1.59] 1.60-1.64/1.65-1.69|1.70-1.74|1.75-1.79|1.80-1.84|1.85-1.89] 
SOFT EE) Te OR SS 
|1.90-1.94|1.95-1.99]2.00-2.04|2.05-2.09|2.10-1.14/2.15-2.19| 
STS Pe IN A | W 
How do these positions compare with the mean for the line? 
