10 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
by Professor Bonney,’ that Darwin has noticed most of the causes on 
which stress is laid by his critics, it should also be remembered that 
Darwin did not observe the phenomena subsequently examined, but 
merely suggested them as possibilities, and his critics may be excused 
for giving their observations a relatively greater value than to his 
theoretical views. 
The whole argument of the great thickness of coral reefs based upon 
the analogy of the so called raised reefs of Cuba, described by Prof. 
Crosby and myself, or of the fossil reefs, is of little value, as it has been 
pretty conclusively shown that these elevated reefs, not only in Cuba 
but in the Pacific, are beds of tertiary limestone intercalated with beds 
of moderate thickness in which corals are found, and the same is true of 
older fossil reefs. Furthermore, these huge masses of tertiary limestone 
which form the substratum upon which both in Cuba and in the Pacific 
recent corals have found a footing, have played no part in the shaping 
of the barrier or encircling reefs, or atolls, which, as we have attempted 
to show, owe their origin in the main to mechanical causes. 
Professor Bonney states that “ Much stress is laid upon the fact that 
many coral islands afford evidences of a certain amount of upheaval; this 
amount, in most cases, is but slight, and its significance appears to me to 
have been exaggerated” ; and he considers these indications to prove only 
oscillation. As far as the Fijis are concerned, the elevation extended 
over the whole group, and: has been shown to amount to more than 
a thousand feet. In Australia it extended along the whole east coast of 
Queensland for more than a thousand miles, and was more than twenty- 
five hundred feet in height! He further says, “If the coral reef be only 
a sort of cap concealing a hill of pre-existent rock, we may reasonably 
be surprised that the ‘ashlar rock’ of coral limestone has in no case 
so far yielded to the action of the atmospheric agencies as to lay bare its 
inner support.” We can answer this point most decidedly. In Florida 
the substratum underlying the recent coral reefs crops out at many 
places, and the highest points of some of the Keys consist of it. So do 
some of the hummocks in the southern part of the Everglades near Key 
Biscayne. In the Bermndas the greater part of the land of that group 
consists of the solian rocks which underlie the recent coral reef. In 
the Bahamas the same is the case, and along the northern coast of Cuba 
the tertiary limestone forming the substratum of the recent reefs crops 
out in all directions, while in Australia rocks underlying the Great Barrier 
1 Loe. cil., p- 824. 
