Vol. XLIX December, 1925 No. 6 



BIOLOGICAL BULLETIN 



ON THE FEEDING REACTIONS AND DIGESTION IN 



THE CORAL POLYP A STRA NGIA DAN&, WITH 



NOTES ON ITS SYMBIOSIS 



WITH ZOOXANTHELL^. 



H. BOSCHMA. 

 ZOOLOGICAL LABORATORY OF THE UNIVERSITY OF LEYDEX. 



In comparison with the extensive literature on the feeding re- 

 actions and the digestion in actinians, these phenomena in madre- 

 porarian polyps have been studied by a few authors only. Our 

 knowledge of these phenomena is chiefly due to Carlgren (1905, 

 Car yophy Ilia), Duerden (1906, Fimgia and Favia), Carpenter 

 (1910, Isophyllia), and Vaughan (1912, various West Indian reef- 

 corals) . In the following pages the results are given of an investi- 

 gation on the feeding reactions and the digestion in the coral- 

 polyp Astrangia dance Ag. 



The work on which this paper is based was made possible by a 

 subvention of the Netherland-America Foundation, which en- 

 abled me to visit the United States for some months. It was 

 carried on in the Marine Biological Laboratory at W'oods Hole 

 (Mass.) in August and September, 1924. I want to thank here 

 the Director of this Laboratory, Dr. F. R. Lillie, for the oppor- 

 tunity I obtained to work some time at this institution. 



The study of the digestion in Astrangia is meant as a base for 

 the further study on the digestion in the polyps of reef-corals. 

 As is well known, the polyps of reef-corals contain a large number 

 of unicellular algae, the zooxanthellae, which are located in the 

 enroderm-cells. Although this association of coral-polyps with 

 algae is generally considered as a kind of symbiosis, there are very 

 few statements on the advantages which both organisms derive 

 from it. One of the ways to investigate this problem is the 

 comparison of the physiology of a form with symbiotic algae with 

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