GROWTH A-Nly AGE AT MATTTEITY OF THE PACIFIC RAZOR CLAM 
227 
immaturity numbered about 17 per cent. A great majority in the fourth year 
(over 75 per cent) and all specimens that were older were completely mature. 
On the Washington beach no such gradual changing over is: found. After the 
clams pass through their second winter they begin to develop reproductive ma- 
terial, and at 2 years of age spawning takes place. Doubtless there are some that 
do not spawn at this age, but none such have been found. The amount of the 
spawn cast is not large, but it does not differ in appearance from the products of 
the larger clams. 
Thus it is seen that on some beds maturity comes on over a period of years. 
In such cases the age at which 50 per cent of the clams are mature (fig. 17) is 
taken as the age of maturity, and as thus determined is found to be 3.2 years at 
r/OO 
-80 
6.0 6.5 9.0 9.5 10.0 10.5 II. 0 11.5 IZ.O 
I 1 1 1 I I I I I 
Length in Cm. 
Pig. 18. — Showing the percentage mature at each interval of length 
Swickshak, 4.2 years at Cordova, and 2 years at Washington. To summarize, 
about one-third of the clams at Cordova and one-half of those at Swickshak and 
all on the Washington beach become mature without passing through an inter- 
mediate stage. Since the clams at Cordova are slower in growth than those at 
Swickshak or Washington, it appears probable that more of them would pass 
through the second stage of immaturity, and this is found to be the case. The 
bearing of size upon maturity will be taken up in the following section of this 
report. 
SIZE AT MATURITY 
The relation of size to maturity has been treated in the same manner as age 
(fig. 18). The percentage of each stage of maturity in each class interval of 
length was calculated and plotted. At Cordova no mature clams of less than 9 
