222 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



(29) Time of sexual maturity. — Female lobsters become sexually mature when from 

 8 to 12 inches long. The majority of all lO^-inch female lobsters are mature. In 100 

 dissections recorded in table 20, 25 females were found, from 9f 6 to 12 inches long, 

 which had never laid eggs, but in 8 of these the ovaries were nearly ripe. Of the 17 

 immature, 6 were lOi inches or over in length, and in most cases the ovaries would 

 not have become mature for two years. 



(30) Frequency of spawning. — The lobster does not spawn oftener than once in two 

 years. The spawniug interval is probably a biennial one, one set of eggs (summer 

 eggs) being laid in July or August (at Woods Hole), and the following set in two years 

 from that time. One has only to examine the ovary of a lobster (see fig. 138, plate 38) 

 which has just hatched a brood — that is, one year from the time of the last spawning — to 

 be convinced that annual spawning is an anatomical impossibility. The conclusion 

 reached from a study of the growth of the eggs is confirmed by the percentage of 

 egg-bearing females captured during the fall and winter. I have shown that conclusions 

 deduced from statistics of this kind are often erroneous, especially when observations 

 have been made in a single locality. When the results of the catch in the harbor of 

 Woods Hole and off No Mans Land were averaged it was found that about one-half 

 of the adult females had external eggs, which accords with the view that the spawning 

 interval is a biennial one. 



(31) Relative abundance of the sexes. — The relative number of males and females' 

 varies considerably in certain localities, as at No Mans Land, May, 1894 (table 22), 

 especially in places affected by the inshore migrations, where the males seem to take 

 the lead. In other places the number of the sexes is about equally divided ; this would 

 always be true if our observations were extended over a sufficient period and area. 



(32) Molting. — By far the greater number of lobsters molt during the months of 

 June, July, August, and September, but there is no month in which soft lobsters may 

 not be caught. The male probably molts oftener than the female, which would accord 

 with the larger proportion of soft male lobsters captured aud with the greater size 

 attained by the male. 



(33) Molting lobsters are more often taken on sandy or weedy than on rocky 

 bottoms. 



(34) In preparation for the molt organic matter is absorbed from the shell, makingit 

 very brittle. Mineral salts are also extracted from certain definite areas of the carapace 

 and chelipeds, an essential condition for the safe passage of the molt. 



(35) In molting, the carapace is raised up behind and the body is drawn out through 

 the opening thus made between carapace and abdomen. Normally, the shell comes off 

 entire, and there is no break in any of the membranes except that between the carapace 

 and the rest of the body. The flesh of the large claws is drawn through the narrow 

 openings of the joints of the limb by the elasticity of the muscles and previous removal 

 of blood from the extremity. This difficult process is also aided by the absorption of 

 lime from certain joints of the old shell. 



(36) The lining of the alimentary tract is molted, and the gastroliths which are left 

 in the stomach are eventually dissolved. Thegastrolith is a specialized part of the lining 

 of the stomach. It is formed in a gastrolithic sac, which is an organ of excretion. It 

 agrees in chemical composition with the rest of the shell, excepting in the greater 

 proportion of calcium salts. The view that the function of the gastroliths is to supply 

 the molting lobster with an immediate supply of lime for the hardening of its soft shell 

 must be abandoned. The gastroliths more probably represent a mass of lime which 



