DEPARTMENT OF MARINE BIOLOGY. 189 



formed a breakwater wall extends far southward beyond the region 

 of coral reefs, and thus it can not owe its origin to corals, but must have 

 been in existence before the corals grew upon it. Vaughan has extended 

 this idea, showing that certainly in the Florida-West Indian region, 

 and probably elsewhere, the modern reefs are growing upon the outer 

 edges of submerged platforms which were formed before the corals 

 began to grow. As is well known, Penck and also Daly have attempted 

 to explain the origin of these submerged platforms as being due to 

 marine corrosion when the tropical sea was lower than at present in 

 the glacial period. Vaughan, however, has not yet committed himself 

 respecting the origin of the platforms. 



Vaughan denies that normal sea- water as such can dissolve limestone, 

 and in this respect his views stand in opposition to those of Sir John 

 Murray and Alexander Agassi z. 



Vaughan's studies in Florida and the Bahamas conclusively show 

 that in these regions the corals are a minor element in the composition 

 of the great limestone banks, and the so-called "coral muds" of older 

 authors are largely oolites which have been derived from chemically 

 precipitated calcium carbonate. 



Dr. Vaughan shows that in southern Florida Pliocene depression was 

 followed by uplift, which was succeeded by depression in Pleistocene 

 times. Then in late Pleistocene times there came another uplift, so 

 that the land was more than 50 feet above its previous level. The 

 region was then again depressed 30 feet or more. The Florida Barrier 

 Reef developed subsequently to the beginning of this last depression 

 seaward of the keys on a platform already prepared for it by marine 

 erosion. The Marquesas was formed by winds and currents, and coral 

 reefs have reestablished themselves at Tortugas after the final sub- 

 mergence of the group. 



Dr. Vaughan's conclusions respecting the somewhat similar changes 

 of level in the Bahamas are stated in his report published herewith. 



Dr. Vaughan has made the most extensive study of the rate of 

 growth of reef corals yet attempted, having been engaged upon these 

 observations since 1908, but as his results have not yet been pubUshed, 

 we are not at liberty to state his conclusions. He also carried out a 

 number of physiological studies upon corals and showed that, in com- 

 mon with other coelenterates, they feed exclusively upon animal matter. 

 He also found that if kept in the dark the ''symbiotic" plant-cells of 

 the corals are much more injuriously affected than are the corals them- 

 selves, thus indicating that the corals are in no essential respect depend- 

 ent upon these plant-cells, but that the reverse is more nearly the case. 

 In another research he found that the more spongy or cavernated 

 corals are better able to withstand exposure to the air, provided the 

 base be submerged, and also that corals are not very sensitive to dilu- 

 tion of the sea-water. 



There are many other interesting and important points in Dr. 

 Vaughan's work, but his biological studies are, as yet, largely unpub- 



