614 J. E. DUERDEN. 
the stomodzum, along with any embedded foreign particles 
in it. 
3. Nutritive substances and extractives placed upon the 
polyp increase the amount of mucus exuded, and also result 
in an opening of the mouth and the institution of an inhalent 
stomodeeal current by reversing the dominant outward beat 
of the stomodeeal cilia. 
4, The mucus exuded as a result of nutritive stimuli is 
drawn down the stomodzeum by inhalent currents in the 
form of distinct streams, and carries with it whatever sub- 
_ stances, nutritive or non-nutritive, are embedded or entangled 
in it. 
5. Ingestion in coral polyps is thus purely mechanical, 
depending upon whatever substances are capable of producing 
an inward beat of the cilia, the opening of the mouth, and 
the exudation of mucus. An inhalent current being esta- 
blished, objects are carried into the polypal cavity without 
regard to their nutritive value, and independently of any 
peristaltic motions on the part of the stomodzeum. 
6. In the ordinary activities of coral polyps inhalent 
currents may be occasionally instituted independently of any 
external stimuli, and these carry with them any inert objects 
resting upon the dise. 
7. Mucus is of much importance in the protection of the 
polypal surface from foreign objects and in keeping it clean, 
and also in the entanglement and ingestion of prey and food 
substances. 
