230 
BULLETIN OF THE BUREAU OP FISHERIES 
a year equal 1 centimeter in length. Like figures obtained from Washington and 
Cordova are given in Table 9. From the maturity line (fig. 19, line W-S^C) 
it is found that a variation of 2.25 years corresponds to a variation of 0.55 centi- 
meter, which gives the following values: 4.10 years equal 1 centimeter; 1 year 
equals 0.244 centimeter. 
Table 9. — Relation of rate of increase of age and length at maturity 
Locality 
Value of 
1 year 
in centi- 
meters 
Value of 
1 centi- 
meter in 
years 
2.26 
2.89 
2.17 
0.442 
.346 
.460 
2.44 
.416 
The figures given immediately above are comparable with the averages of 
Table 9. In growth, therefore, one year corresponds) to 2.44 centimeters, but in 
maturity one year corresponds to 0.244 centimeter. The influence of a year in 
growth is thus ten times as great as in the process of maturing; or, from the stand- 
point of size, 1 centimeter corresponds to 0.416 year in age, but in maturity 1 cen- 
timeter corresponds to 4.10 years. The influence of a centimeter in growth is thus 
one-tenth as great as in the process of maturing. The ratio (1 to 10) thus obtained 
compares very favorably with that above (1 to 13), when tlie differences in methods 
are taken into account. 
MATURITY IN OTHER FORMS 
The relation of age and length to maturity given for the razor clam does not 
hold in all forms. The work of Thompson (1914) on the halibut shows that these 
vertebrates mature at nearly the same aA^rage age in different localities, while the 
average size varies quite widely. However, there is a difference in average age at 
maturity which, although slight, may be accounted for by the difference in average 
size. For example, fish from Hecate Straits mature at an average of 12 years of 
age and 40.7 inches in length, while those from Kodiak Island Banks mature at an 
average of 12.3 years and 35.4 inches. Thus, there is a variation in age of 0.3 year 
in 12, or 2.5 per cent, and in size of 5.3 inches in 35.4, or 15 per cent. The con- 
clusion is, then, that a difference of 15 per cent in size at maturity between these 
two banks is accompanied by a difference of 2.5 per cent in age, which shows in 
this form that age and length influence maturity in the ratio of 6 to 1, age being 
the more important. 
We offer no explanation for the maturing of halibut according to age and of 
clams according to size. Figures for other species are not available. The work 
of Baldwin (1921) and Crampton (1908) give data on the size and age of boys 
and girls at maturity, which further analysis may show to be similar to one of the 
above cases. 
