NATURAL HISTORV OF AMERICAN E 
363 
It is shown, however, by Hadley, that the rate of growth is more rapid in the young 
Wickford lobsters (stages i to 17), that it begins to fall at the age of about lyi years 
(stage 18), becomes differentiated in the sexes in favor of the more rapid growth of the 
male at the twenty-third stage, and continues to decrease, the stage period becoming 
longer and longer with age, especially in the female, where the production of eggs pro- 
ceeds at a very rapid rate. Thus, according to Hadley, the increase in the 12-inch lob- 
ster has dropped to 9 per cent, or about one-half that in the first 17 stages, and while both 
sexes have molted 25 times, the male is but 7 years old, while the female is 10 years and 
4 months. Thus he thinks that the female is outstripped in the race with the other sex 
on account of the drain upon her vitality due to the periodic production of a rapidly 
increasing egg supply, and that this accounts for the fact that so far as observed giant 
lobsters beyond 18 or 20 inches in length are invariably of the male sex. 
