602 J. E. DUERDEN. 
It is manifest that ciliary activity is an important factor in 
the physiological activities of actinian and coral polyps, par- 
ticularly in combination with mucus, as will be more fully 
discussed later. ‘The exhalent currents produced thereby 
serve to waft or float away whatever inert particles accumu- 
late upon the disc, while the inhalent currents are of much 
significance in ingestion. The cilia are shown to react locally, 
and only upon direct contact with the stimulating substance, 
that is, their activity is not dependent upon nervous impulses, 
either near or distant. 
EXPERIMENTS WITH F'AvIA. 
For a study of the reactions and feeding activities of 
colonial corals a species of Favia was employed. The indi- 
vidual polyps are here about 8 mm. across, and the tentacles 
are closely arranged at the margin of the disc, so that those 
of adjacent polyps intermingle on full expansion (fig. 6). 
Compared with those of Fungia the tentacles of Favia take 
a greater part in the activities of the polyp. 
When very light débris is dropped upon acolony of Favia 
with the polyps fully expanded, the lighter particles are caught 
in the exhalent currents from the various stomodea, while the 
heavier fall on the disc, and become embedded in the super- 
ficial layer of mucus. ‘he free floating particles over any one 
polyp are wafted rather quickly from the mouth towards the 
tentacular region, beyond which they seem about to pass, when 
they are immediately checked, in such a manner as to demon- 
strate that between the individuai polyps there is either an 
approximate neutral zone or one in which the current moves 
upwards (fig. 4). 
The marginal regions, where the tentacles from adjacent 
polyps intermingle, thus become occupied by particles driven 
to and fro within very narrow limits; sometimes the objects 
pass more over the disc of one polyp, and then further over an 
adjacent polyp. Ultimately, however, the particles come to 
