GROWTH AND MORTALITY OF PACIFIC RAZOR CLAN 
555 
(1920) and subsequently for the Pismo clam (Weymouth, 1923a), by Brody (1923), 
and by Munford (1926) for the growth of various domestic mammals. This relation 
however fails in old age 
Q/no Number 
Figure 7. — Absolute growth curve of clams from Hallo Bay, Alaska, with the first 
differential 
when the growth is greater 
than would be predicted on 
this basis. 
Relative growth . — T o 
picture the relative or 
percental growth, recourse 
may be had to the ratio 
diagram as used by the 
economist. Here equal pro- 
portional or percental 
changes are represented by 
equal vertical distances. 
Such a diagram is obtained 
if we plot the logarithms 
of the total length on age, as 
in Figures 8 and 10. Such 
a curve rises most steeply at 
first, and the slope contin- 
ually declines throughout 
life. Or, as before, we may plot the percental yearly gains which show a continually 
decreasing increment during the period for which we have data. (Figs. 8 and 9.) 
Comparison oj absolute and relative treatments . — With these two methods of 
presentation before us, let us contrast the pictures. The differences lie chiefly in 
early life; the slow 
growth of old age differs 
little whether regarded 
from the absolute or the 
relative viewpoint. The 
early growth, however, 
appears in a very differ- 
ent light when presented 
by these contrasted 
methods. As stated 
above, the absolute 
growth of small clams 
is slow. This later be- 
comes more rapid with 
its maximum at the 
point of inflection, after 
which it again declines. 
The relative growth, on 
the other hand, is most 
rapid at the youngest 
ages for which we have records and steadily declines with time. Obviously, as with 
other statistical procedures, both pictures are true and necessary to complete pres- 
entation. Which, however, represents the more significant point of view? Unless 
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,4 
, 1 
O 123456769 /0 
G/ng Number 
Figtjke 8— Ratio diagram of growth of clams from Hallo Bay, Alaska, with the first 
differential 
