Polychoerus carmelensis — Armitage 
205 
placed in each of 10 plastic bowls. Two addi- 
tional bowls were filled with gravel and 10 
worms were placed in each. All the bowls were 
placed in an aquarium with the sides and top 
covered to keep out all light. In addition, the 
room was also darkened. Sea water from the 
laboratory system was circulated around the 
plastic bowls as a temperature control. The num- 
ber of animals visible in each bowl was deter- 
mined approximately every 2 hr. from 0800 until 
2200 hr. for 2 days and spot-checked for 2 more 
days. The counts were made under a dim light. 
During the first day there was a gradual in- 
crease in the number of worms that were visible. 
This leveled off by the morning of the 2nd day. 
The number of animals visible at the time of 
each count for the 2nd day is given in Table 1. 
There is no relationship between the number of 
animals visible and the time of day or the con- 
dition of the tide. Nor did the subsequent spot 
checks indicate any relationship. From this it is 
concluded that P. carmelensis does not show 
any diurnal or tidal rhythm of activity. 
Observations in the field indicated that P. 
carmelensis came to the surface during low tide 
when the water was quiescent in the tide pools 
and when the light was relatively dim. If one 
waded through a pool in which the animals were 
located, one could observe the animals begin a 
downward movement. A similar downward 
movement was observed when the first waves of 
the incoming tide reached the pool. These ob- 
servations indicated that water agitation was the 
stimulus for movement downward. 
The following laboratory experiment tested 
the field observation. The data in Table 1 show 
that there was not much variation in the num- 
ber of animals visible in the plastic bowls in 
the darkened aquarium. The number observed 
was particularly stable in the plastic bowls with 
gravel. Two bowls with rocks and two bowls 
with gravel were lighted sufficiently so that the 
animals could be counted. There was no reaction 
to the light in any of the dishes. Each of the 
bowls with gravel had 10 animals visible. One 
bowl was shaken gently; all the animals imme- 
diately became active and began crawling down 
into the gravel. After 3 min., only 2 worms were 
visible and both of them were crawling. All 10 
animals remained visible in the control dish 
which was not shaken and only 1 animal was 
active. There were 5 worms on top of a rock 
in a third bowl. When this bowl was agitated, 
all the worms became active; 4 of them crawled 
under the rock within 2 min. The other animals 
in the bowl also became active, but could not 
move down as they were on the bottom of the 
dish. There was no activity in the fourth bowl, 
which also had a rock and served as an unshaken 
control to compare with the third bowl. From 
these experiments and from the field observa- 
tions, it was concluded that P. carmelensis is 
negatively geotaxic in quiet water and positively 
geotaxic in agitated water. 
TABLE 1 
Total Number of Animals Visible in Plastic Bowls with Rock and with Gravel 
(Ten animals were placed in each bowl) 
TIME OF 
NO. VISIBLE IN 
NO. VISIBLE IN 
TIME OF TIDE 
OBSERVATION 
8 BOWLS WITH ROCK 
2 BOWLS WITH GRAVEL 
0800 
56 
19 
0810 low 
1000 
64 
20 
1200 
62 
20 
1400 
48 
19 
1444 high 
1500 
54 
19 
1600 
62 
20 
2000 
51 
20 
2105 low 
2200 
53 
17 
