A METHOD OF LOBSTER CULTURE. 231 
individuals, having passed through the moult and recovered their strength and 
appetites, are very destructive to the smaller or freshly moulted larve. The 
effects of this discrepancy in the ages among lobsters of one batch are especially 
injurious when the older individuals reach the fourth stage, for the fourth-stage 
lobsters are endowed with strength, sagacity, directive power of movement, 
and voracity of appetite far beyond that of the other stages. When, through 
a difference in age, a number of lobsters enter the fourth stage considerably 
in advance of the others, they become veritable ‘“‘sharks,’’ as they are jocularly 
called by the attendants. On this account in the first experiments with wooden 
cars a considerable loss was sustained because certain boxes were reserved as 
hatching boxes and the fry rather than the ‘“‘hens”’ were periodically removed 
(fig. 5, pl. 1x). It being impossible to get them all out at one time, those that 
remained were often taken out together with a younger lot and later on became 
“sharks” to this brood. 
Circulation current.—For the benefit of the fry there is no doubt an optimum 
current within the car. The current can be controlled to a surprising degree 
by manipulating the propellers, although the number of revolutions per minute 
remains constant. A slight inclination to the blades makes a current very 
slow, while the maximum inclination creates a current like a mill race. The 
length of the blades, the amount of taper from base to apex, and the height 
of the blades in the water cause different effects in the character of the current; 
for example, the relations of the rotary and the upward components of the cur- 
rent can be thus controlled and varied within wide limits. By these and other 
variations the fry can be made to scatter evenly at all depths and distances 
from the center or to occupy various zones or strata. Experience and judg- 
ment must decide the question of optimum current at each particular phase. 
In general, it may be said that a gentle, even current made by a long, well- 
tapered blade and slight angle of inclination is usually best. 
Containers for eggs and jry.—When the rearing was done in canvas bags 
the old lobsters were confined in crates suspended in the bags, because, if let 
loose in the bottom, they were apt to tear the canvas. The crates were neces- 
sarily less spacious and had the objection of being in the way of the newly 
hatched fry, which were sometimes swept against them with considerable force 
by the current. To the other advantages of the wooden car as compared 
with the canvas bag must be added its capacity to function as a hatching pen. 
The design and construction of these wooden cars, together with many other 
recent improvements, should be credited to Mr. E. W. Barnes, the superintendent 
of the station. 
In the beginning of the experiments at Wickford the fry were transported 
from the Woods Hole hatchery by the Bureau of Fisheries, with whom we 
were in cooperation. Later experiments showed that the eggs could be stripped 
off in the usual way and placed in small rearing bags, where they would hatch. 
