606 J. E. DUERDEN. 
with them whatever foreign particles are resting upon the 
disc or tentacles. 
The nature of the foreign objects ingested is of no signifi- 
cance. When the reactions set up by a nutritive solution are in 
progress, any substance whatever, coming within the influence 
of the incurrent stream of mucus, is swallowed. Neutral 
bodies, such as small grains of sand, fragments of shells, or 
pieces of paper, which have been resting upon the discal surface 
for some time become covered with mucus and are indrawn 
into the widely-opened mouth. Even particles situated as 
far outwards as the margin of the tentacular zone come within 
the influence of the stomodeal currents, and are slowly 
carried centrally and ingested. The act of ingestion is thus 
purely mechanical; the polyps exercise no such faculty as 
choice as regards the substances which enter the gastro- 
vascular cavity. It is simply a question of the influence of 
different solutions upon the stomodzeal cilia. When the latter 
are stimulated they react directly, without any other part of 
the polyp being concerned, so as to produce an inhalent current, 
and any object upon the discor tentacles is drawn downwards 
whatever its nature, whereas when the cilia are producing an 
outward current all objects upon the disc are rejected. 
The reactions of the polyps of Favia towards solid nutritive 
substances, such as fragments of meat or crab’s muscle, are 
of much the same nature as those towards nutritive solutions. 
The close contiguity of the polyps often renders it possible 
for several mouths to reach the same fragment and all attempt 
to ingest it. Under these circumstances the food is pulled at 
from many different directions, but in the end one polyp 
generally succeeds in securing the whole. ; 
Distant polyps in the colony, that is those not directly 
touched by the food substances, are stimulated to activity by 
diffusion of the juices, and respond by opening their mouths 
and instituting an inhalent current. The polyps also possess 
to a remarkable degree the power of protruding the peristome 
and directing it towards the source of the stimulus (directive 
ieee 
