LIFE HISTORY OF THE BLUE CRAB. 97 
The number of eggs contained in a sponge of average size is enormous. S. I. 
Smith places it at 4,500,000,4 which number was quoted by Herrick.’ Paulmier ¢ 
estimates that between 2,000,000 and 3,000,000 eggs are borne in the sponge. The 
present author found that by actual count there are about 200 eggs upon each hair 
of the swimmeret. The hairs occur in fairly regular bundles of about 5 each, there 
being about 20 bundles in each of the 11 rows, arranged in a longitudinal manner, 
on the swimmerets. There are 8 swimmerets. Computing these figures gives the 
sum of 1,760,000. It must be borne in mind that this figure is not much more than 
an estimate, as it is next to impossible to determine accurately the number contained 
in such a large mass of objects as minute as the eggs in question. ‘The most accurate 
statement that can be made is that there are from 1,750,000 to 2,000,000 eggs in a 
sponge of the usual size. 
The eggs had been fertilized while in the body of the female. This process is 
described on page 117. 
The eggs are carried upon the swimmerets while their development goes on, or 
during what might be termed the “‘period of incubation.” About 15 days are required 
for the eggs to hatch. A female crab was kept under observation in a float (Pl. LI, 
fig. 20, and Pl. LV, fig. 37).2 On June 15 this individual threw out a sponge. 
On June 29 it was found that some of the eggs had hatched, since there were many 
empty shells upon the swimmerets. By July 2 nearly all the young had hatched out 
and left the mother. In this case it will beeen that the period of incubation was from 
14 to 17 days. Another crab was observed to spawn on August 15. The eggs hatched 
within 12 to 15 days. The temperature of the water, no doubt, has some effect upon 
the duration of the incubation period. During the last of June, when the first experi- 
ment was being carried on, the temperature of the water was about 79° F. During 
the August experiment the water was about 85° F. This may account for the fact 
that the eggs hatched somewhat more quickly in the latter than in the former case. 
It has been thought by some that the young crabs cling to the swimmerets of the 
mother for a time after hatching. Binford,’ however, observed the young as they 
hatched from two females and found that this was not the case. The present author, 
in the case of the two crabs used in the experiments just described, found that the shell 
of the egg split into two parts (Pl. XLVIII, fig. 5), the young crab emerged and, after 
freeing itself from a thin membrane which covered it, swam away. Numerous empty 
split shells (Pl. XLVIII, fig. 10, and Pl. LII, fig. 30) were found on the swimmerets of 
the adult, but no young crabs were observed clinging there. Several other crabs were 
observed as the eggs were hatching, but in no case were any young found clinging to 
the swimmerets. 
It is thought by many that the young, immediately upon hatching, turn about and 
devour the mother crab. Needless to say, this idea is a mistaken one, although, of 
course, quite small crabs feed upon and may even consume any dead crab which they 
chance to find. In fact, this erroneous notion arose from the occasional observation of 
@Smith, S.I.: Report on the Decapod Crustacea of the Albatross Dredgings. Report of Commissioner of the Fishand Fisheries 
for 1885, pp. 618-619. Washington. =) 
» Herrick; op. cit., p. 309. 
¢ Paulmier, F.C.: The Edible Crab. ssth Annual Report, N. Y. State Museum, rgor, p. 134. 
d Unless otherwise stated, all of the experiments discussed in this paper were carried on at Hampton, Va., between October, 
1916, and October, ro17. 
€ Binford, R.: Notes on the Life History of Callinectes sapidus. Johns Hopkins University Press, February, ror1, p. 1. 
