THE ROLE OF MUCUS IN CORALS. 603 
rest among the tentacles in the somewhat neutral region, and 
settle in the interpolypal spaces below. Any new particles 
coming into the area of motion of an individual polyp are at 
once wafted from the mouth towards the periphery, and are 
there battered to and fro until in the end they settle among 
the tentacles. Sometimes the particles are whirled round 
and round over the oral aperture for some time before being 
driven away. 
The superficial layer of mucus containing the heavier 
particles is ultimately freed, the mucus being formed into 
shreds or patches. These in their turn are wafted peri- 
pherally and accumulate among the tentacles, their further 
Fie, 4.—Distribution of particles dropped upon a colony of Favia 
when exhalent currents are in progress. Three polyps are repre- 
sented in section. 
progress outwards being arrested by the currents from 
adjacent polyps. ‘The boli usually revolve round and round 
for some time, and then sink between the tentacles into the 
spaces between the surrounding polyps. 
Somewhat similar results were obtained from experiments 
with carmine, sepia, and taleum powder in sea-water. The 
fine particles from the diffusion cloud were at first distributed 
uniformly over the surface of the disc and tentacles, having 
become embedded in the mucus. Usually after afew minutes 
the mucus began to break into patches or shreds, and was 
then floated towards the intermingled tentacles, through 
which it passed to the columnar areas below. 
Very rarely the carmine or sepia, embedded in mucus, 
