CORALS 93 



number. They were made by fixing funnels and 

 inverted bottles over the surfaces of corals living in a 

 suitably protected pool to collect the gases given off. 

 The latter were then exploded with hydrogen, made 

 by the action of acid on zinc, to determine the oxygen 

 present. If correct they show an extraordinary 



FIG. 28. A GROUP OF THE POLYPS OF MILLEPORA EXPANDED 

 (" CHALLENGER "). 



From the system of tubes common to the colony rise five mouthless 

 individuals, which serve as tentacles to the central individual, 

 which takes from them the food and digests it. Further 

 observations on living material are much needed. 



activity in coral growth, but they are open to some 

 doubt, and should be repeated. At the same time 

 experiments might conveniently be made on the effect 

 of sediment, of various sized particles and kinds, on the 

 surfaces of the corals, to see how far the anemones 

 possess any power of cleaning mud and sand off their 



