364 
bulletin of the bureau of fisheries. 
Following Hadley’s estimate still further, for the larger lobsters, upon the age or 
rate of growth of which no data are yet available, a male lobster 19^/^ inches long is 20 
years old and has passed successfully 32 molts, while a mammoth measuring 22^ inches 
from beak to telson has entered upon his thirty-sixth stage, and attained to the green 
old age, for a lobster, of 33 years. According to my earlier estimate a lobster at the 
thirtieth molt had attained a length of 19.1 inches. 
That the stage periods increase with age no one can deny, for this is only another 
way of saying that youth is the period of most active growth. There is no theoretical 
limit to the growth of such a crustacean, although there is a practical limit. Thus lob- 
sters do not attain a weight of 100 pounds, but they have tipped the scales at 34 pounds. 
Again, there is no a priori reason for assuming that the percentage increase in weight in 
the adult lobster at each molt may not be fairly uniform up to the period of decline. But 
since molting is not only the prelude to expansion in size, but also of the greatest use to 
the animal in freeing it from troublesome parasites and messmates and at the same time 
keeping its cuticular glandular system in order, as well as in the repair of injuries through 
the restoration of appendages and other lost parts, we should surely expect to find so 
useful and necessary a process limited only by the duration of life itself. This is appar- 
ently the case, and since the tendency, in all the higher organisms, at least, is to lose 
vitality with age we might expect the percentage of increase in weight or in the expan- 
sion of the body to decrease gradually in old age until it was practically nil, or reduced to 
the ability of renewing the shell or exoskeleton only. This would seem to be actually 
the case, although we have no direct observations upon which to found the opinion, and 
it is possible that death from old age in the lobster, if it come at all, would follow from 
fin al failure to cast the heavy armor, rusty with age, and scarred in many a conflict. 
As has already been noticed in considering the rate of growth of the ovary (p. 299) 
the volume of any part or of the body as a whole does not increase proportionately with 
the length but more nearly with the cube of the length. In other words the percentage 
increase in the length of the body at each molt does not accurately express the true rate 
of growth, which concerns the entire volume of the body. Therefore it may be found 
that after a period is reached corresponding to the length of from 8 to 10 inches, the 
lobster, and more particularly the male, may increase more rapidly in volume and become 
stockier, especially to be noticed in the enlargement of the big claws, while increase in 
total length of the body may be relatively less. 
I have shown that the male, length for length, weighs more than the female, and 
that a female with external eggs is lighter than one of the same length without eggs 
{149, p. 118-120, table 31); it is therefore only natural to expect to find the female 
handicapped by the male after reaching sexual age (j}i to 12 inches). 
We will now briefly consider the rate of growth of Woods Hole lobsters, average 
increase per cent 15.3, and that of Wickford lobsters with average of 18 per cent for the 
first seventeen stages, or 18.4 per cent as given in another place. Hadley in attempting 
to account for this discrepancy concludes that the former figure is too low and that it 
does not represent the growth of young lobsters under natural conditions at Woods Hole. 
