FEEDING REACTIONS IN CORAL POLYPS. 411 



less hungry polyps are very susceptible to a certain stimulus, as 

 is the rule in anthozoans. On the contrary well-fed polyps react 

 very slowly on the same stimulus. Also in this respect Astrangia 

 agrees with other anthozoans (cf. Jennings, 1905). 



The chief results of my experiments on Astrangia are published 

 in a preliminary paper (Boschma, 1925), in which especially the 

 role of the zooxanthellre in the feeding of the polyps is compared 

 with that in other anthozoans. 



FEEDING REACTIONS. 



The reactions of Astrangia to food and other substances are in 

 many respects quite similar to those found in other representa- 

 tives of the anthozoans. Before the results of my own investi- 

 gations on Astrangia a short summary of the literature on this 

 subject is given below. 



Pollock (1883) was the first to describe that sea-anemones may 

 perceive the presence of food-particles in their neighborhood, as 

 this causes the opening of the mouth and movements of the 

 tentacles of the animals. Loeb and Nagel some years afterwards 

 worked out the reactions to food and other substances in actinians 

 more in detail. According to Nagel (1892, 18940, 18946) the 

 actinians have a sense of taste, which is located only in the 

 tentacles, and the food is brought to the stomodaeum by muscle- 

 action. Nagel (18946) already stated that hungry actinians also 

 ingest morsels of paper besides lood-particles, whereas well-fed 

 ones will only take food. The results of Loeb (1891, 1895) 

 differed in some respects from those of Nagel. The phenomenon 

 which was called by Nagel the "sense of taste" is according to 

 Loeb a reaction to chemical stimuli. Loeb showed that the 

 tentacles are not the only organs in which the response to chemical 

 stimuli is located, he stated that also ciliary actions plays a part in 

 the feeding of actinians. Moreover by cutting an actinian into 

 two halves Loeb proved that a part of such a polyp devoid of its 

 tentacles even takes food more readily than a normal individual. 



Parker (1896) confirmed Loeb's results that ciliary action is one 

 of the chief factors in the feeding of actinians. Parker found that 

 the cilia of the stomodaeum generally beat outwards, but when 

 food substances come into contact with these cilia they reverse 



