JUNE 28, 1912] 
tion, as toward food; and it is not until the 
fourth stage is reached that the lobster can be 
truly said to be master of its own movement. 
It was learned in the early stage of the inves- 
tigations on the behavior of the fourth-stage 
lobsters that, if any study at all was to be 
made of their reactions to light, the lobsters 
must first be fed—and well fed. For, if such 
was not the case, the tendency to eat one 
another usually annihilated any possible 
manifestation of a response to the influence of 
light or other stimuli. Even if the condition 
of hunger did not excite these extreme canni- 
balistie instincts, and so preclude all experi- 
mentation, it produced a manifestation of un- 
rest which made any results in the way of 
numerical counts impossible. As has been 
shown in earlier papers, the fourth stage- 
period, at least in the early part, is typic- 
ally a “swimming-period ”—the “swimming- 
period” par excellence of the lobster’s whole 
existence. It is not until the latter part of 
the fourth stage-period that the lobster, under 
the proper conditions of environment, goes to 
the bottom and begins to burrow in the sand 
or under the bits of shell. Now it was found 
that the condition of hunger appeared to have 
a very definite influence upon the time at 
which this burrowing “instinct” was first 
“liberated” in the fourth-stage lobster. To 
determine this point, several experiments were 
performed of which the following is a fair 
example of all. 
Experiment A 
Influence of Hunger on “ Burrowing.’— 
On August 5 about thirty early four-stage 
lobsters were taken from one of the confine- 
ment bags, in which they were being reared. 
They did not show much evidence of hunger 
and were therefore isolated for 48 hours with- 
out food. At the expiration of this time, all 
proved to be very hungry. Now two groups of 
five lobsters each were taken from this lot, 
and each group was placed in a 14 em. erystal- 
lization dish, the bottom of which was cov- 
ered with sand, gravel and shells. Immedi- 
ately after this, one group of lobsters was fed 
with chopped clam meat; the other group was 
SCIENCE 
1001 
left hungry. The dishes were then placed on 
the laboratory table, and records were taken 
frequently to ascertain at what time the bur- 
rowing would be first manifested; and in 
which group of lobsters—the fed or the unfed. 
For some little time the members of both 
groups swam more or less constantly at or 
near the surface. Further records, which 
show the time of burrowing of the individuals 
in the two groups, may be presented as fol- 
lows: 
Group Fed 
Group Unfed 
Time 
Aug. 7, 10:00 a.m. | 1 larva bur- | 5 larve swimming 
rowed. or crawling. 
Aug. 7, 11:30 a.m. | 2 larve bur- | 5 larve swimming 
rowed. or crawling. 
Aug. 7, 3:30 P.M. | 3 larve bur- | 5 larve swimming 
rowed. or crawling. 
Aug. 8, 9:00 a.m. | 4 larve bur- | 5 larve swimming 
rowed. or crawling. | 
Aug. 9, 9:00 a.m. | 4 larve bur- | 3 larve burrowed.” 
rowed. 
Aug. 9, 6:00 p.m. | 4 larve bur- | 4 larve burrowed. 
rowed. 
These results appear to show that hunger 
may postpone the liberation of the burrowing 
instinct, while satiety appears to favor its 
early appearance. One other experiment, and 
the converse of the previous case, may be in- 
troduced. 
Experiment B 
Influence of Food-stimulus wpon Surface- 
swimming in the Fourth-stage Lobsters.—In 
this case about twenty mid and late fourth- 
stage lobsters were placed in a glass jar 25 cm. 
in diameter filled with salt water to a depth 
of 10 em. These lobsters were kept without 
food until they showed evident signs of 
hunger. All the lobsters remained on the 
clean bottom of the jar, over which they 
crawled or lightly swam. Occasionally one 
would come to the surface, only to leave it 
again for the bottom of the jar. Now a long 
pipette was partly filled with fresh clam juice, 
and the outside of the pipette carefully washed 
to take away all possible trace of clam odor 
? At this point in the experiment one of the five 
lobsters was killed and eaten by the others, three 
of which immediately burrowed. 
