6G CORAL AND ATOLLS 



but, after a day or two of this life, tbey settle down, and 

 become fixed to some object by the end that is pointing 

 forwards as they swim — that is, the end farthest from the site 

 of the future mouth. 



When first liberated they are opaque and solid bodies, 



Fig. 9. 



Two Young Growths op Srriatoj)ora that have started 

 THEIR Colonies upon a Living Oyster. 



and it is not until some days of their free existence have 

 been passed that the dimple of the mouth begins to pene- 

 trate the solid body and hollow it out, and then the larva 

 swells somewhat and becomes transparent. In colour the 

 newly liberated larva is usually yellowish. As is so frequently 

 the case in the adult, this is due to the presence of Zooanthellye, 

 which are vegetable cells living in the tissues of the coral. 



