138 W. J. MOENKHAUS 
TABLE 5 
NUMBER PAIRS | NUMBER PAIRS | NUMBER PAIRS |PER CENT PAIRS PER CENT PAIRS 
TESTED | FERTILE INFERTILE FERTILE INFERTILE 
POMEL ymae eae Se 50 27 23 53 47 
1ONO Ae .. 51 49 2 96 4 
(eee 51 39 12 77 23 
TCS) ea 52 44 8 85 15 
ilo Lae ee 35 24 1 69 31 
Average fertility of 239 pairs 75 per cent. 
taken to select from. Five pairs were again taken as before. The 
results appear in table 6. 
Thus it will be seen that all five pairs showed a uniformly high 
degree of fertility. The average fertility of all the pairs was raised 
to 93. 8 per cent. 
5. Discussion 
From the above series of experiments a number of important 
facts are brought out. 1. Sterility, as it appeared in the strain 
under consideration, is strongly transmissible through inheritance. 
2. It is readily controlled by selection. 3. Inbreeding is probably 
not the physiological cause of it. 
That this sterility is transmissible cannot be doubted. The 
faithfulness with which this occurs appears in the strains A and B. 
Both were derived from a common pair that showed a variability 
with respect to this character in the three pairs of its offspring 
TABLE 6 
NUMBER PAIRS NUMBER PAIRS NUMBER PAIRS PER CENT PER CENT PAIRS 
TESTED FERTILE INFERTILE | PAIRS FERTILE | INFERTILE 
BMG ces, , 41 37 4 90 10 
(Oye: Ue 45 42 ene} 93 7 
DOGS rete: ee 45 44 1 97 3 
Di hy ee ee ys 36 33 3 91 9 
Is eee eee 44 42 2 95 5 
Average for 211 pairs 93.8 per cent. 
