A. O. POWYS 
241 
Fig. 3. Number of Offspring and Average Duration of Life of Mothers. 
A, Mean Lifetime after 45 Years of Age, by Survivors of Age 46. 
B, „ „ 60 ,, ,, ,, 60. 
C, ,, „ 75 „ ,, „ 75. 
24 
23 
22 
21 
20 
19 
18 
17 
1 16 
i 
^ 13 
o 
1 
^. 9 
^ 8 
7 
6 
5 
4 
3 
2 
1 
0 
c 
r 
A 
L 
/ 
'-\ 
y — 
./ 
CC , )/ : 
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 
Size of Family. 
Equations to Kegression Straight Lines : 
.r = 1 child. 
Equations to Cubical Parabolas : 
= 23-32576- -08538.!; -•01864.!.- -•00071a;MOrigin at 8 5 children. 
= 13-94679- -21964^;- -02765x2- ■00032.cMUnit of x=l child. 
aa', 
y 
= 22-7306 + -09666,E 
bb', 
y 
= 23-7906 - -08834,r 
dd', 
V 
= 14-0067 + -02959a; 
ee' , 
y 
= 16-9808 --35757^; 
gg', 
y 
= 7-3196 + -01410.r 
hh'. 
y 
= 9-7714- -27662a; 
ii', y= 7-20525- -15409.r--00816.i;- + -00135jr' 
Biometrika iv 
(Origin at 8 children. 
(Unit of .r = l child. 
31 
