AGE AND GROWTH OF THE PACIFIC COCKLE 
635 
favorable years. The unusual uniformity of the data, due to the high correlation of 
the growth from year to year in the same individual, has resulted in very smooth 
growth curves. Figure 3 shows the uniform course of growth of two large individuals 
taken at Kukak Bay and at Port Moller, respectively. 
AGE IK YEARS 
Figure 3. — Individual growth of Cardium corbis at Kukak Bay and at Port Moller 
The same data may be further analyzed, and the differential of the first curve 
or the absolute annual increments may be plotted as in Figure 4 V. This curve shows 
Figure 4. — The velocity (V) and (A) of the absolute growth of Cardium 
corbis at Snug Harbor 
the velocity or time rate of growth and is useful to make conspicuous relatively slight 
variations in the curve, such as the presence of growth cycles. 
The differential of this velocity curve — that is, the second differential of the orig- 
inal growth curve — represents the acceleration of the growth. Most growth data are 
29386—31 2 
