Feeding Habits of Hippa — Matthews 
laboratory where antennae, antennules and 
the contents of the dissected digestive sys- 
tems were examined microscopically for evi- 
dence of filter feeding. 
C The methods employed in B were re- 
peated, one week later. Sand crabs collected 
were taken to the laboratory and the anten- 
nae, antennules and contents of the dissected 
digestive systems examined microscopically 
for evidence of filter feeding. 
D. Approximately equal portions of Ulva, 
Velella , shrimp and Physalia were separately 
ground with sand and sea water, filtered 
through number 40 mesh grit gauze and each 
filtrate (approximately 25 cc.) diluted to 1,000 
cc. of sea water. Each solution was thrown on 
the thin film of a receding wave and the 
effects, if any, noted. For each solution, a new 
location on the beach was chosen. Again, 
sand crabs which responded to any of the 
solutions were taken to the laboratory where 
antennae, antennules, and the contents of the 
dissected digestive systems were examined 
microscopically for evidence of filter feeding. 
E. Twenty-five male and 25 female sand 
crabs were collected and their compound eyes 
were removed leaving the major portion of 
the eye stalks intact. These blinded sand crabs 
were placed in a small tank and allowed one 
day to recover from operative shock, during 
which time they received additional sea water. 
Physalia was again ground in sand and sea 
water, filtered through number 40 mesh grit 
gauze and the filtrate (25 cc.) diluted with 
approximately 1,000 cc. of sea water. The 
diluted filtrate, colored with 0.5 grams of 
neutral red was placed in a clean, 1 liter bottle 
fitted with four discharge pipettes. Adjust- 
ment of a single Hoffman clamp permitted 
the simultaneous, drop by drop, delivery of 
the filtrate into four paper cups (300 cc. capac- 
ity) each of which contained beach sand, 
sufficient to cover the bottom 2 cm., and 75 
cc. of sea water, sufficient to produce a water 
depth of 2 cm. Four sand crabs were simul- 
taneously tested: (1) a control male, (2) a 
control female, (3) a test male, and (4) a test 
383 
female; each in a separate paper cup. In no 
case was the filtrate introduced until all four 
sand crabs had buried themselves in the sand. 
Ten drops (approximately 0.5 cc.) of filtrate 
were simultaneously introduced into each of 
the four paper cups and the reaction time 
recorded. This was regarded as the interval 
from the instant the tenth drop struck the 
surface of the water, to any visible response 
by the crab. The observed times, both for 
control and test animals, was averaged for 
five separate trials. After each experiment, 
paper cups and contents were discarded. These 
blinded sand crabs and the controls were also 
examined microscopically for evidence of fil- 
ter feeding. 
F. The methods employed in E were re- 
peated (with fresh paper cups, sand, and sea 
water) except that both the compound eyes 
and the antennae were removed. 
G. The methods employed in E were re- 
peated, except that the compound eyes and 
the antennules were removed. 
H. An attempt was made to test crabs with 
compound eyes, antennae and antennules 
removed. However, only 24 (of 50) sand crabs 
survived the severe operative shock. Of these, 
over half remained on their backs on the 
surface of the sand, displayed little or no 
action and were dead the following morning. 
The colored Physalia solution was introduced 
to the remaining 12 survivors in the small 
tank and the results noted. These crabs were 
dead on arrival at the laboratory and I regret 
that the contents of their digestive systems 
were not examined microscopically. Male and 
female controls were run as before (E,F,G). 
RESULTS 
A. Microscopic examination of sand crab 
antennae and antennules collected during the 
high surf revealed sand grains but no organ- 
isms enmeshed in the setae. The dissected 
digestive systems, especially the pyloric caeca, 
were blue, gorged with nematocysts and the 
shredded remains of Physalia zooids. There 
were no microorganisms nor was there any 
