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PACIFIC SCIENCE, Vol. II, July, 1948 
onto a rock 6 inches from a crab; the crab seemed 
frightened and returned to the water, completely 
ignoring the meat. However, 4 minutes later, the 
crab returned, seized the meat, and readily devoured it. 
Other pieces of abalone saturated with CS 2 were 
tossed near crabs on a dry ledge. On each occasion 
the fragments were eaten in a normal manner. More¬ 
over, one crab conveyed a fragment of abalone into 
the blind employed for these observations, an act 
which provided an unusual opportunity to test the 
reaction of the crab to odors registered as repugnant 
by humans. Carbon bisulphide was actually poured 
over this piece of meat as the crab ate it; the crab 
at no time exhibited any visible sign of adverse stim¬ 
ulation. 
Experiment 6: The eyes of two large crabs were 
covered with a mixture of shellac, lampblack, and 
plaster of Paris. Subsequent to the application of this 
paint, the crabs would not react to shadows or move¬ 
ments. One crab was allowed to wander over the 
rocks until it remained stationary in a suitable crevice. 
A fragment of pungent abalone viscera was held 
within 1 centimeter of the oral field for 3 minutes. 
No response whatsoever was elicited. No antennal 
movement occurred although Bethe (1896, 1897) 
noted movement under similar circumstances for C. 
maenas\ antennal movement occurs when the identical 
procedure is followed with P. crassipes immersed in 
water (see below). The meat was immediately 
grasped if it was brought into contact with the 
chelae. When it touched the dactyl of the second 
ambulatory leg, it was thrust under the body to the 
chelae and subsequently eaten. 
The above experiment suggests that this species 
apparently does not react to odors. However, upon 
contact of the chelae and dactyls with the meat, the 
manipulation of the morsel into eating position was 
rapid. Whether or not the fleshy consistency of the 
food provided the correct stimulus for this behavior 
cannot be irrevocably demonstrated; however, some 
clarification was effected in a later experiment. 
The identical procedure was repeated with a blinded 
crab in an aquarium. Whenever crabs are submerged, 
the antennules, antennae, and oral appendages move 
continually. It was necessary, therefore, to note the 
increase in movement of one or all of these structures 
to ascertain whether or not a response was elicited 
from an introduced stimulus. A fragment of abalone 
intestine was held 4 inches from the posterior end 
of the crab. After 15 seconds the antennules, antennae, 
and chelipeds moved far more rapidly than normally, 
registering stimulation by the food. The water was 
changed, and a new piece of meat was held 1 inch 
from the posterior end; increased appendicular move¬ 
ments were noted in 10 seconds. This procedure was 
repeated with the meat suspended immediately above 
the carpus of the ambulatory legs; a response was 
noted in 15 seconds. The procedure was again repeated 
with the meat suspended 1 inch in front of the oral 
area; a response was noted after 45 seconds. 
It is apparent that the direction of the respiratory 
current is responsible for the differential response to 
the food. The respiratory current enters the bran¬ 
chial chamber laterally and leaves it anteriorly via 
a trough, thereby conveying chemical stimuli to the 
receptors on the antennules as the current emerges 
from the respiratory chamber. These facts would 
seem to clarify, in part, the factors underlying the 
backward approach to food sought by these crabs, 
inasmuch as detection of food via chemical means is 
accomplished more rapidly from the lateral or pos¬ 
terior than from the anterior areas. 
Experiment 7: Ten blinded crabs were placed in 
individual aquaria; a fragment of art gum eraser was 
placed in contact with the dactyl of the second ambu¬ 
latory leg of each. The second walking leg was em¬ 
ployed here not only because it is the longest, but 
because field observations indicated that it was the 
one most frequently utilized by the crabs to test 
objects immediately below them. The crabs gathered 
the bits of eraser beneath them, grasped the frag¬ 
ments with the chelae, and conveyed them to the oral 
area, whereupon they were immediately rejected. 
The above procedure was repeated with a small 
clean pebble substituted for the eraser. The pebble 
was completely disregarded in all cases; the animals 
exhibited a slightly disturbed response and moved 
an inch or two away from the pebble. 
The experiment was again repeated, with pieces of 
liver substituted for the pebbles. The gathering re¬ 
sponse was similar to that shown the eraser, but the 
liver was eaten after it had been conveyed to the 
mouth. 
Although the above experiments are not con¬ 
clusive, they do supplement characteristic field 
behaviorisms which aid in affixing a partial 
evaluation of the comparative utility of the 
senses in the procurement of food. It is appar¬ 
ent that all three senses are employed; more¬ 
over, the degree of individual participation of 
the senses seems to depend entirely upon the 
conditions which prevail at any given time. 
Vision was definitely relied upon in portions 
of all experiments except where the eyes were 
rendered opaque. Visual response to food stimuli 
seemed apparent early in each experiment, which 
implies that movement of the food material 
was significant. Instantaneous response to food 
materials some distance away can be regarded 
