43O H. BOSCHMA. 



organisms of the superficial water of the sea. Hickson (1906) 

 admits that the zooxanthellae may constitute a part of the food of 

 reef-corals, but thinks it improbable that there are coral-polyps 

 that feed exclusively on their yellow cells. In a recent work of 

 Hickson the opinion is upheld that probably "the holozoic 

 method of nutrition of the coral is supplemented by the holophytic 

 action of the chlorophyll-bearing zooxanthellae" (Hickson, 1924, 



p. 21). 



The other opinion on the food of reef-corals is expressed by 

 Vaughan (1912, 1919) after a great number of feeding experiments 

 on West Indian reef-corals. His conclusion is that the food of 

 reef-corals solely consists of animal matter. This view is also 

 supported by Mayer (1918), who based his opinion on Vaughan's 

 experiments and on the statement of Duerden (1904) that the 

 polyps of Siderastrea are easily kept alive with meat of crabs and 

 other animals. 6 



Vaughan's opinion was first criticized by Gravier (1913). Ac- 

 cording to Gravier it is improbable that coral-polyps live ex- 

 clusively on animal matter, for their symbiotic algae are un- 

 doubtedly also a factor in their nutrition as direct food or 

 indirectly by the supply of carbohydrates. After the study of the 

 contents of the coelenteron of many coral-polyps I also (Boschma, 

 1924) came to a conclusion differing from Vaughan's. I found 

 that the food-remnants in the gastric cavity of the polyps of reef- 

 corals always contained zooxanthellae in various stages of disinte- 

 gration, undoubtedly owing to their being digested by the polyps. 

 Besides these algae also animal matter was found in the remains of 

 the food, rarely in the smaller polyps, more often in the larger 

 polyps. 



It is generally understood that the products of the photo- 

 synthesis of the zooxanthellae assist in the nutrition of the 

 ccelenterates containing these algse (Buchner 1921, 1924; Hickson, 

 1924). In many anthozoans which harbor large quantities of 

 these unicellular algae even a degeneration of the food-capturing 



6 Besides the facts on the food of reef corals there are some statements on the 

 food of madreporarian corals which do not contain zooxanthellae in their entoderm. 

 Some notes on the food of deep-sea corals are found in the publications of Gravier 

 (1920) and Boschma (1924). In the latter article also data on the food of species 

 of Dendrophyllia from shallow water are given. Cf. also Gardiner's articles on 

 Ccenopsammia and Flabellum, cited above. 



