222 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
(29) Time of sexual maturity. — Female lobsters become sexually mature when from 
8 to 12 iucbes long. The majority of all 104-inch female lobsters are mature. Iu 100 
dissections recorded iu table 20, 25 females were found, from 9f e - to 12 inches long, 
which had never laid eggs, but in 8 of these the ovaries were nearly ripe. Of the 17 
immature, G were 10^ inches or over in length, and in most cases the ovaries would 
not have become mature for two years. 
(50) Frequency of spawning. — The lobster does not spawn oftener than once in two 
years. The spawning 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 iu the harbor of 
Woods Hole and off Ho 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 Ho 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 and 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, making it 
very brittle. Mineral salts are also extracted from certain definite areas of the carapace 
and chelipeds, an essential condition tor the safe passage of the molt. 
(35) In molting, the carapace is raised up behind and the body is drawn out thrpugh 
the opening thus made between carapace and abdomen. Hormally, 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 whicb 
