THE ROLE OF MUCUS IN CORALS. 599 
of even the lightest particles can be observed around it or 
anywhere else on the discal area; light objects may remain 
resting on the disc for hours, which would certainly not be 
the case if the disc itself, or even the tentacles, were ciliated. 
When, however, the mouth is opened and fine inert particles 
are dropped around it, they are seen to be at once wafted 
away, passing rapidly outwards in a continuous stream 
along with other light objects which may be lying upon the 
disc. 
Objects resting upon the disc are moved in a very uniform 
manner once their translation commences; there are no 
subsidiary movements in the neighbourhood of the tentacles 
or any restricted part of the disc such as would be expected 
were cilia present. In some instances the mouth closed 
while the bodies were in the act of gliding towards the 
discal margin; the gliding motion then ceased, and the 
objects came to a state of rest upon the disc and remained 
there. Further, when the living tentacles or parts of the 
discal surface of Fungiaare examined under the microscope 
there is no evidence that cilia are present. 
From all these we may conclude that the outer surface of 
Fungia is not ciliated,! and that any motion of particles 
upon its disc or in its vicinity is entirely due to currents of 
water produced by the cilia lining the stomodzeum. 
The experiments also render it manifest that under ordinary 
circumstances the outward beat of the cilia is the more usual 
in Fungia, and that the inward beat is produced by the 
action of what we may consider to be nutritive substances. 
Further, the inhalent current is maintained only so long as the 
stimulating agent continues to act; after this there is a cessa- 
tion, and then, following a greater or less interval, there is a 
reversal of the dominant beat, leading to an exhalent current. 
1 Carlgren has recently published a paper in which he shows a considerable 
variation in the extent of the ciliated surface both in actinians and corals 
(‘‘ Uber die Bedeutung der Flimmerbewegung fiir den Nahrungstransport bei 
den Actiniarien und Madreporarien,” ‘ Biol. Central.,’ Bd. xxv, 1905, p. 308). 
