FEEDING REACTIONS IN CORAL POLYPS. 413 



oesophageal cilia, and of the transverse mesenteric muscles. 

 Only the muscular reactions are under the control of the animal 

 as a whole. 



The feeding reactions of Alcyonium are described by Pratt 

 (1906). In this form the tentacles are the chief organs for the 

 capture of the food. The species exhibits a definite choice in 

 selection of the food, as eggs of fish and of Galathea are not 

 digested, whilst the polyps readily feed upon planktonic organisms 

 and flesh of different fishes. 



There are only a few papers dealing with the feeding reactions 

 in madreporarian polyps. The first species, in which obser- 

 vations on the capture of the prey are recorded, is Astrangia dance. 

 Verrill and Smith (1874) mention that it catches its food with the 

 tentacles, which afterwards transfer the food to the mouth. De 

 Lacaze-Duthiers (1877) made some feeding experiments with 

 Caryophyllia Smithii and Balanophyllia regia. In the former 

 species the food, a piece of a living mollusk, placed on the oral 

 disk, caused a depression of the disk in this place. By the action 

 of the muscles of the oral disk it was now brought to the mouth. 

 The tentacles remained quite inactive. In Balanophyllia on the 

 contrary the tentacles pushed the food towards the mouth. 

 After some time in both species the food was discharged through 

 the mouth covered with mucus. These statements, however, 

 can hardly represent the normal behavior of the polyps. Proba- 

 bly the animals were in an abnormal state, for De Lacaze- 

 Duthiers had kept them during several years in captivity. More- 

 over these statements are not in accordance with those by Carl- 

 gren (1905) on Caryophyllia. According to Carlgren the tentacles 

 of this species catch food-particles and deposit them on the central 

 part of the oral disk. By ciliary movement they now are trans- 

 ported over the oral disk to the stomodaeum and swallowed. 



The polyps of Siderastrea radians seize the food, according to 

 Duerden (1904), with the tentacles. According to the same author 

 (Duerden, 1905) mucus plays an important part in the feeding 

 reactions of Fungia and Favia. On the surface of the polyps a 

 mucous layer is secreted. Small organisms which come into 

 contact with the oral surface of the polyps are imbedded in the 

 mucus, which is afterwards ingested. 



