The Comatulids of Torres Strait. 115 
the arms, and the arrangement and appearance of the ciliated furrows, 
it is evident that the comatulids at Maér obtain their food, living 
vegetable plankton, directly from the sea-water by means of the 
ciliated furrows and that the arms serve no essential purpose in feeding 
other than the multiplying and extending of these furrows. 
If this view is correct, a plentiful supply of sea-water containing an 
abundance of the necessary plankton would be the essential factor in 
controlling the distribution of these comatulids, and their local occur- 
rence about the island might throw some light on the matter. The 
island of Maér is surrounded on all sides by a fringing reef between 
which and the shore itself is a reef-flat of great extent, as much as 
600 yards wide on the southeast side of the island. The reef is lacking 
only at one point, the west-south-west corner of the island, but it is 
nearly wanting at the southern point also. Between these two gaps 
the southwestern reef is very rich in corals and in other animal life. 
Directly across a channel, about a mile wide, lie the islets Dauer 
and Weier, also surrounded by an extensive fringing reef. Through 
this channel the tidal movement is very marked, spring tides at the 
Murray Islands rising not less than 10 feet. On the southeastern 
reef there is constant surf breaking (at least during the southeast 
trades of the dry season), but the tidal movement on the flat itself is 
not particularly active. At the northern end and on the west side 
of the island, neither surf nor tide is as marked as on the other side. 
We examined the reef and the reef-flat on all sides of the island and 
were constantly searching for crinoids. Young Comatula purpurea 
were found practically everywhere in water that was well aerated, 
but no large comatulids were found anywhere on either the western 
or northern parts of the reef. On the southeast reef-flat, Comatella 
maculata was fairly common and occasionally a Comanthus annulatum 
or a Lamprometra would be found there; but we soon learned that 
when we wanted crinoids in any numbers, the southwestern reef was 
the place at which to obtain them. They occurred there in great 
abundance, and especially near the outer margin of the reef the number 
of species and the size of the individuals were notable. A natural 
explanation of this fact is that the great tidal movements through the 
channel between Maér and Dauer maintain a richer supply of vegetable 
plankton at that point than is to be found on any of the other reefs. 
It may be added that the abundance of food is, as will be shown later, 
only one factor in making the southwestern reef so attractive to 
comatulids. 
RESPONSE TO LIGHT. 
Almost the first fact noted with reference to the habits of the 
comatulids at Maér was that they showed an evident tendency to 
withdraw from brightly illuminated areas. On overturning a rock- 
fragment on the lower surface of which crinoids were living, they at 
once began to move. Sometimes they withdrew into dark holes or 
