DESCRIPTION OF THE EXPEDITION. 7 
and other plans would not allow us to devote as much attention to this point as we 
should have liked. Consequently we had to select our dredgings carefully, each 
for its own specific purpose—and the collections from this source are disappointing 
in quantity, though perhaps not in quality. 
The distribution of the shallow-water organisms of marine slopes presents problems 
very similar to those of the land. It is Eeronlicated; in many classes by the presence of 
pelagic larvee *, and by forms with extraordinary powers of existence on floating weed 
or timber. Again, environment appears to be so much less varied than on land + that, 
the problems of convergence and parallelism become correspondingly more acute. 
However, our own work at Minikoi and in the Maldives impels us to believe that 
though involved at every turning in numerous possibilities, some light will be thrown 
on the question of the pre-existence of former land-areas by the study and comparisons 
of littoral faunas and floras. For such work our area appeared particularly suitable, 
and we accordingly carefully collected the fauna and flora of each locality visited, 
making specialities of Salomon Atoll and Coetivy {. 
Our own researches in previous expeditions have been largely concerned with the 
formation and growth of coral-reefs and the bionomics of the organisms which form 
them. It will be obvious to what an important extent these are related to the 
previous problems. All research on these questions, if rightly applied, is of practical 
importance, but the main scientific interest lies in the question as to whether coral- 
islands owe their origin to subsidence or not. Granting that a land-connection once 
existed between India and Madagascar, we should surely expect to get an idea of its 
topography traced out in some degree by coral-reefs, if it fell victim to a gradual 
subsidence (unless, indeed, physical conditions were then vastly different—a not im- 
possible contingency). ‘To elucidate this point we were careful to fill as many gaps in 
our knowledge of the ocean-floor as possible. Particularly we aimed at getting all 
possible information about the topography of the Chagos Archipelago in view of its 
either half-drowned or upgrowing banks; and here it will be enough to state that in this 
group of atolls, which have been the subject of much controversy, not a single bottom- 
sounding previously existed between any of its shallower banks. We felt, moreover, 
the necessity for further information of every character about the totally submerged 
* Vide “ Notes and Observations on the Distribution of the Larve of Marine Animals,” by J. Stanley Gardiner, 
Ann. Mag. Nat. Hist. ser. 7, vol. xiv. (Dec. 1904). 
+ We would at once point out ihat the faunas found on the slopes of continental lands barred by coral-reefs, 
and those not so protected, are very distinct even in non-reef-building animals. The mere fact of a slope being 
calcareous or siliceous appears to cause a divergence. Again, there may be differences between the animals on 
continental coral-slopes and the coral-island slopes in their immediate vicinity, such as actually exist on those 
of Ceylon and the Maldives and Laccadives. But this instance perhaps may be really due to the inability of certain 
animals to cross the intervening seas. Everywhere the presence or absence and the nature of the scaweeds’ is 
a factor of primary importance to the fauna. Enough, however, has been said to show the caution required 
in dealing with the problems that arise. 
+ While, on the one hand, we might hope to lay foundations (in the study of the possibilities of dispersal from hp 
cA distribution of littoral organisms) for the more accurate delineation of land and sea in past ages, we cannot 
be blind to the fact that, if a land-connection disappeared along our line by slow and long-continued subsidence, we 
may have at every point remains of a littoral fauna once continuous throughout the whole line, 
SECOND SERIES.— ZOOLOGY, VOL. XII. 2 
