DERIVATION OF THE FLORA AND FAUNA 321 



island groups — such as Fiji, New Caledonia, and New Zealand — appear to have been 

 isolated at much earlier periods than others, such as New Guinea, the East Indies, 

 and Japan. 



3. The ancient borderlands of the continents have, in part at least, suffered un- 

 dulatory submergence. Compensatory forms are the deep ocean trenches, on the one 

 hand, and the mountain ranges of the continents, on the other. 



4. The Pacific is a relatively deep and unstable area, whereas the Atlantic — with 

 the exception of the broad intersected belt of activity directed toward the equator — 

 has, on the whole, been relatively stable since the Palaeozoic. 



5. The western area of the Pacific appears to possess a more complex structure 

 than the eastern, owing to the earth's rotation, the width and weakness of the Pacific 

 base, and the resistance opposed to this activity by the stable continental masses of 

 Eurasia and the Australian— Sahul area. 



6. The islands of the Pacific lying within the area bounded by the ocean trenches 

 have not had continental histories, nor do they appear ever to have had actual and 

 direct land connections with the continents. 



7. The New Hebrides and Tongan Islands, and possibly also the Pellew and Mari- 

 anne groups, appear to partake in some measure of the nature both of "continental" 

 and "oceanic" islands. 



We shall have occasion to return to Andrews' opinion on the origin and his- 

 tory of Pacific floras. Here it seems convenient to draw attention to the numerous 

 submarine cones called "guyots" recently discovered in the sea between Hawaii 

 and the Marianas and discussed by Hess (1J2). About 160 flat-topped peaks, 

 presumably truncated volcanic islands, rise from 9000 to 150CO feet above the 

 deap-sea bottom. In most cases their flattened summit was sounded in about 800 

 fathoms. Hess' working theory is that they were formed on land, sunk to their 

 present level and levelled by sea action — this would mean that they stood with 

 their summit at sea level long enough to be exposed to wave action. Thus, 

 drowned reefs could be expected, but no such are reported: the guyots are, 

 Hess thinks, very ancient structures dating from a "proterozoic episode of vul- 

 canism", they are of pre-Cambrian age and consequently do not lend themselves 

 to biological speculations. There may, however, have existed later islands, both 

 Paleozoic and Mesozoic, but all have disappeared beneath the surface of the ocean, 

 either built up again by reef-building organisms or sunk to a depth where these 

 cannot live. The high volcanic islands are very young, perhaps not even Tertiary 

 but Pleistocene or recent, because the rocks could rarely be proved to be of Ter- 

 tiary age. We shall see by and by that the endemic insular floras and faunas cannot 

 be anything like recent. "Oceanic islands", Hess continues, "are and have always 

 been slowly sinking relative to sea level" as a consequence of the accumulation 

 of bottom sediments causing the water level to rise. The red clay increases i cm 

 in loooo years, the globigerina ooze the same amount in 5000 years. Thus millions 

 of years are needed to account for even a very moderate submergence. Besides, 

 raised shore-lines are, in many cases, unmistakable proofs of local emergence. 

 The melting of the great inland ices ought to have had a greater influence. 



Finally, let us listen to one of the foremost authorities on geophysics, GUTEN- 

 BERG (i2j). He finds (p. 7) that there is 



21 -557857 The Nat. Hist, of Juan Fernandez and Easter Isl. Vol. I 



