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 messm ates and at t he sam e time 

 keeping it.s cuticular glandular system in order, as well as in the repair ot injiirips throug h 

 the restoration of. appendages and other lost parts, we should surely expect to find so 

 ricpfi^^ QnH npppgggry c) pf^ cess limited only by the 'duration of life itse lf! 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 nU^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 

 final 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. 1 1 8-1 20, table 31); it is therefore only natural to expect to find the female 

 I handicapped by the male after reaching sexual age {7J4 to 12 inches). 



We will now briefly consider the rate of growth of Woods Hole lobsters, average 

 increase per cent 13^3, and that of Wickford lobsters with average of iSjjer 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. 



