284 THE BIOLOGY OF HYDRA : 1961 



exerts a pH effect. Now wlien the light is shining on the algae, free 

 CO2 is rapidly photosynthesized and the pH goes up to maybe 11 

 or 12. 



GOREAU: Corals have alkaline phosphatases with optima at 

 about pH 11.0 (Goreau, 1953, P.N.A.S. 39: 1291). We thought 

 at first that these enzymes were concerned with calcifica- 

 tion, but results of our histochemical studies (Goreau, 1956. Na- 

 ture 177: 1029) make this appear unlikely. 



LOOMIS: Under illuminated conditions you get precipitation 

 of calcium carbonate through increase of pH. Therefore, COo has 

 two roles in calcification: one as the carbonate ion, and one as free 

 CO2. 



GOREAU: I am not sure that I agree with you. I wish we could 

 measure CO2 and pH in living calcifying corals. Let me comment on 

 the first part of your question regarding differential growth at tips 

 and sides of branches in Acropora cewicornis. Actually conditions 

 are almost certainly not identical at the tips and sides of branches. 

 This species has an inborn factor which controls the rate and pat- 

 tern of calcification in the colony — and thus determines colony 

 shape. It is a function inherent in the coral not the zooxanthellae, 

 and within some limits seems to have little relationship to photo- 

 synthetic carbon fixation as I mentioned in my talk. 



PHILLIPS: How long a period of photosynthesis do you allow 

 in these experiments? 



GOREAU: Approximately 6 hours, 



PHILLIPS: Bean and Hassid (Assimilation of C^^Oo by a Photo- 

 synthesizing Red Alga, Iridophycus flaccidum. Bean, R. C. and 

 W. Z. Hassid. 1955. /. Biol Chem. 2i2;411-425) found in their 

 studies an assimilation of C^Oo in Iridophycus flaccidum, a ma- 

 rine red algae, that 90 odd percent of the C^^ was in an alcohol- 

 soluble phase. Alcohol extraction might be a possible way of 

 getting around your wet ashing. What is the method you use? 



GOREAU : It is a modification of a technic published by Folch 

 and Van Slyke. Instead of using a mixture of concentrated sul- 



