182 
MB. A. B. WALLACE ON THE ZOOLOGICAL 
their sister science, and by means of the humble weeds and de- 
spised insects inhabiting its now distant shores, can discover some 
of those past changes which the ocean itself refuses to reveal. 
They can indicate, approximately at least, where and at what 
period former continents must have existed, from what countries 
islands must have been separated, and at how distant an epoch the 
rupture took place. By the invaluable indications which Mr. 
Darwin has deduced from the structure of coral reefs, by the 
surveys of the ocean-bed now in progress, and by a more extensive 
and detailed knowledge of the geographical distribution of animals 
and plants, the naturalist may soon hope to obtain some idea of 
the continents which have now disappeared beneath the ocean, 
and of the general distribution of land and sea at former geological 
epochs. 
Most writers on geographical distribution have completely over- 
looked its connexion with well-established geological facts, and 
have thereby created difficulties where none exist. The peculiar 
and apparently endemic faunae and florae of the oceanic islands 
(such as the G-alapagos and St. Helena) have been dwelt upon as 
something anomalous and inexplicable. It has been imagined that 
the more simple condition of such islands would be to have their 
productions identical with those of the nearest land, and that their 
actual condition is an incomprehensible mystery. The very re- 
verse of this is however the case. We really require no specula- 
tive hypothesis, no new theory, to explain these phenomena ; they 
are the logical results of well-known laws of nature. The regular 
and unceasing extinction of species, and their replacement by allied 
forms, is now no hypothesis, but an established fact ; and it neces- 
sarily produces such peculiar faunas and floras in all but recently 
formed or newly disrupted islands, subject of course to more or 
less modification according to the facilities for the transmission of 
fresh species from adjacent continents. Such phenomena therefore 
are far from uncommon. Madagascar, Mauritius, the Moluccas, 
New Zealand, New Caledonia, the Pacific Islands, Juan Hernan- 
dez, the West India Islands, and many others, all present such 
peculiarities in greater or less development. It is the instances 
of identity of species in distant countries that presents the real 
difficulty. What was supposed to be the more normal state of 
things is really exceptional, and requires some hypothesis for its 
explanation. The phenomena of distribution in the Malay Archi- 
pelago, to which I have here called attention, teach us that, how- 
ever narrow may be the strait separating an island from its con- 
