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PACIFIC SCIENCE, Vol. IX, October, 1955 
evidence, either from nematocysts or zooids, 
that Velella had been eaten. 
B. As the wind subsided and Physalia and 
Velella no longer appeared in the surf, pieces 
of algae (Ulva fas data, Turbinaria ornata, 
Sargassum obtusi folium, Poly opes darionensis) , 
Velella and shrimp tossed into the thin film 
of receding waves all failed to evoke any 
visible response from sand crabs but when 
Physalia was used, sand crabs emerged. Often 
4 or 5 would seize a single colony simul- 
taneously and, submerging, all take part in 
pulling it below. Others, often arriving at the 
scene too late and finding no prey, would 
quickly submerge as the wave receded. It was 
not difficult to collect 25 or more sand crabs 
by using a single Physalia colony over and 
over again in this manner. Microscopic ex- 
amination of the antennae and antennules 
revealed sand grains but no organisms en- 
meshed in the setae. The dissected digestive 
systems were, as before, gorged with nema- 
tocysts and the blue remains of shredded 
Physalia , but no microorganisms were present. 
C. As in B, when the waves of the calm sea 
broke on the beach, no crabs responded to 
Ulva. However, when Velella, commercial 
shrimp, and Physalia were tossed separately 
onto this region of the beach, crabs emerged. 
Microscopic examination of antennae and 
antennules again revealed sand grains but no 
organisms enmeshed in the setae. The dis- 
sected digestive systems were empty save for 
sand grains and what appeared to be mucus. 
D. Filtered and diluted portions of »ground 
Ulva, Velella and shrimp thrown on receding 
waves failed to evoke any visible response 
from the submerged crabs. However, when 
the Physalia filtrate was used sand crabs 
emerged, excitedly ran up and down the 
beach but, failing to locate the Physalia, 
quickly submerged. Microscopic examina- 
tion of the antennae and antennules of these 
collected sand crabs revealed a few sand 
grains but no microorganisms enmeshed in 
the setae. Again the dissected digestive sys- 
tems revealed nematocysts and the bluish re- 
mains of Physalia but no microorganisms. 
E. Of the 50 sand crabs collected for this 
part of the experiment, only 18 males and 15 
females survived the operative shock of eye 
removal. Many, even when molested, re- 
mained motionless on their backs; others 
righted themselves and, colliding one with 
another scurried around the tank. Finally, 
without any definite pattern of orientation, 
most submerged. Although the Physalia solu- 
tion was clearly discernible as it left the four 
pipettes and entered the salt water of the pa- 
per cups its course became less apparent as 
it approached the sand so that determination 
of the exact moment of contact of filtrate and 
crabs was impossible. This condition was 
often further complicated by the spontaneous 
emerging of crabs before the first drop of 
filtrate could possibly have reached them. The 
addition of 0.5 grams of neutral red to the 
solution made it easy to follow the course of 
the filtrate. Sand crabs in all four cups emerged 
in great confusion during the introduction of 
the first six drops of filtrate. It was impossible 
for me to determine whether the control males 
and females or the blinded males and females 
responded more quickly. Microscopic exam- 
ination of test and control crabs revealed only 
a few sand grains enmeshed in the setae of 
antennae and antennules. The digestive sys- 
tems contained the remains of Physalia but 
there was no evidence of microorganisms. 
F. Of the 50 sand crabs collected for this 
experiment, only 30 survived the operative 
shock of the removal of both the eyes and 
antennae. These exhibited about the same 
activities as those described in E. Again there 
was much confusion. Some turned over on 
their backs, whereas others, colliding one with 
another, hurried around and around the tank 
and finally, without special orientation, sub- 
merged. Compared to crabs having only the 
compound eyes removed the reaction of these 
crabs to the introduced filtrate was dilatory 
and weak. Often 3 to 5 minutes elapsed after 
