A. O. POWYS 
37 
Mr Powys' statistics have been fitted with a cubical parabola in Figure 4*. 
Its equation is 
y = 6-165,263 + 0-160,401a' - ()-047,676*^ + 0•002,788«^ 
the origin being at 57'5 years ajid the unit of x being five years. In fitting a 
range of 85 years, i.e. 15 to 100 was taken, omitting the data for 100 — 105 as 
too few to give a trustworthy average. The corresponding curve for English 
mothers is 
y = 6-4092 + 0-079,120a; - 0-052,719^^ + 0-005,717ar' 
with the same origin and unit for x. 
Fig. 
40 50 60 70 
A (f e of 31 other at Death 
4. Theoretical Curves for Buration of Life and Number of Offspring. Great Britain, America, 
New South Wales. With New South Wales Experience. . 
In Figure 4 the theoretical curves for English, American and Australian 
mothers are plotted on the New South Wales observations, and the comparison is 
of considerable interest. The English Quakers, it has been noted, show a tendency 
to have lessened offspring with parents li\ ing to great ages, and this tendency is 
even more marked in the case of New South Wales. Although the extreme tails, 
90 — 100 years, of all three curves are of small value, yet there certainly appears to 
be a difference between the American on the one hand and the English and 
Australian mothers on the other. We are now more justified than we were in 
June 1900-f-, in asserting that extreme longevity is not in all cases favourable to a 
maximum reproductivity. But our warning against rushing to hasty conclusions is 
confirmed, for a new community like New South Wales with plenty of food and 
occupation for all is seen to resemble an old community like England in this 
relationship, and not a new community like America. Under certain conditions 
we thus see that Weismann's views may be correct : women living to 60 — 70 may 
leave more offspring than either those who die younger or those who die older. 
* I am responsible alone for this bit of work. K. P. 
t Loc. cit. p. 166. 
