326 
bulletin of the bureau of fisheries. 
lining terminates abruptly at the forward end of the rectum, but this is not the case 
in early life. 
During the course of development the ova increase considerably in size, and, losing 
their original globular form, become distinctly oblong (fig. 33, a and b). The bright red 
pigment cells or chromatophores, which are distributed in a characteristic manner, 
particularly on their basal segments and on the sides of the carapace, are prominent 
for a long time before hatching. These, together with the interference colors of the 
huge eye-spots and the rich green of the unabsorbed yolk, give the eggs of the lobster 
exceptionally brilliant color patterns. 
EXCLUSION AND DISPERSAL OF THE BROOD. 
o 
o 
Fig. 33. — Outlines to show relative sizes 
of lobsters' eggs when laid (a), and when 
ready to hatch (6). Enlarged about 
$ l A diameters. 
It was found that when the eggs at the point of hatching were removed from the 
mother lobster and placed in jars at Woods Hole a full week elapsed before the entire 
brood was set free. Possibly the period is shorter when the animal is undisturbed 
and left to her own devices in the sea. When other conditions are favorable, the warmer 
the water the more rapid will the emissions occur. The individual variation in the 
eggs entailed by the long period of fosterage render it certain that all can not hatch 
simultaneously. Fullarton {113) found that in the Euro- 
pean lobster the time required for the hatching of a 
brood varied from one to three weeks or even longer, 
but it is not likely that this period is extended to very 
great lengths under natural conditions. 
The egg-bearing lobster instinctively folds its tail, 
thus securely inclosing the eggs in the abdominal pocket 
when in danger of enemies, while at other times she is seen at intervals to extend her tail 
and, standing upon her legs and incurved tail fan, move her swimmerets back and forth. 
In this way the eggs are aerated and cleaned, and such actions proceed instinctively during 
the 10 months of parental care which they receive. The cargo of eggs shows the effects of 
the treatment, for they pass the storms and stress of winter with remarkably little loss, 
and come to point of hatching bright and clean. It is rare to detect a single barren egg 
or broken embryo among the thousands of perfectly formed young. Yet when the egg- 
bearing lobster or crayfish are too closely confined, or the normal conditions of their 
environment seriously disturbed, sediment soon clogs the eggs and parasitic protozoa 
and other organisms attack and destroy the egg glue to such an extent that the ova 
fall off of their own weight and soon perish. 
It might prove to be a point of some interest to determine whether the rhythm 
of the swimmerets is fairly uniform or not from the beginning to the end of the period 
of fosterage, but nothing can be said on this subject at present. 
The behavior of the American lobster at the time of the emission of the young 
has not been studied with sufficient care under natural conditions; accordingly, I tran- 
scribe the following observations made on the European species by MM. Eabre-Domergue 
and Bietrix ( 101 ). 
