322 Editorial Comment. 
The shells fall through a solvent medium, are attacked on all 
sides, constantly washed clean for a fresh attack, and constantly 
meeting fresh portions of the liquid. Masses of coral limestone 
in a lagoon are, on the other hand, attacked only from above, 
are protected by the debris of their own disintegration, as well 
as that falling from the surface or swept in by currents, and are 
long in contact with the same liquid particles. 
The readers of Nature will find much to interest and instruct 
them in the charts given by Capt. Wharton of the Tizard, 
Macclesfeld, and Prince Consort banks. The central portion 
of the Tizard bank is from thirt}^ to forty-seven fathoms in 
depth, with a rim of living coral rising within four to ten 
fathoms from the surface, some small patches of reef even 
reaching the surface. The other two banks are similar except 
that the coral is deeper in the water. Wharton maintains that 
the progressive development of these banks will result in atolls 
with deep lagoons, for the production of which neither the 
subsidence assumed by Darwin nor the solution assumed by 
Murray, is needed. 
His facts will certainly tend to emphasize the opinion ex- 
pressed at the close of his communication, that a better know- 
ledge of the physical and biological phenomena of coral 
formations is requisite to settle the theoretical disputes about 
them. 
Mr. John Murray, however, demurs to the proposition that 
ovu" knowledge is so very limited at present, and re-aftirms his 
faith in the solution theory. 
In the same number of Nature (March i ) Prof. G. C. Bourne 
contributes additional facts derived from the study of living 
corals at Diego Garcia, and the Great Chagos, Pitt, and Centu- 
rian banks. His conclusions are, as he puts it, " nearly identical" 
with those of Capt. Wharton. He adds however, what seems 
to us an important suggestion, viz., that currents by their too 
great violence, or their entire absence, have more to do with the 
absence of living polyps in lagoons than the supply of food. 
At Diego Garcia "the most luxuriant coral patches are found 
at the south end of the lagoon, furthest away from the lagoon 
outlet." In this case the food supply, which may be assumed 
to enter by the "lagoon outlet," is manifestly not the most es- 
