PROBLEMS OF DISTRIBUTION AND THEIR SOLUTION. 161 



day and generation, groping successfully enough after the true cause 

 of the likeness between the anima)s of Albion and Gaul. In the 

 Neotropical region of the geologist, the Island of Trinidad presents 

 us with an excellent example of the bearing of geological change 

 over the distribution of life. Geographically, Trinidad is one of the 

 West Indian Islands ; zoologically, Trinidad is a part of South 

 America. Whilst the animals of the West Indian Islands are highly 

 peculiar, as we have seen, those of Trinidad resemble the animals 

 found in the neighbouring American area ; and along with Trinidad 

 we may class the islands of Tobago, Margarita, and Cura9oa as 

 zoologically belonging to the South American continent, and not to 

 the Antilles. Close to Trinidad lie Grenada, Barbadoes, and St. 

 Vincent ; yet the geographical nearness of these three latter islands 

 to Trinidad is completely overturned by the facts of distribution. 

 What theory of the constitution of living beings and of the earth at 

 large is competent to explain the immense differences which separate 

 Trinidad and neighbouring islets in a zoological sense from the 

 Antilles ? On the theory of special creation, no explanation is pos- 

 sible. On the hypothesis of evolution, the main outlines of the 

 problem and its solution are clear enough. The relations of Trinidad 

 and South America are in reality the counterpart of those which 

 Verstegen assumed existed between the " Isle of Albion" and Gaul. 

 At a relatively and geologically " recent " date, there was land con- 

 nection between Trinidad and the American continent such is 

 the geological phase of the question. The biological aspect shows 

 us a sufficient reason for the likeness of the fauna of Trinidad to 

 South American life, by assuming that the processes of variation 

 and change in its species have not yet had time sufficient at their 

 disposal to establish differences of importance. Conversely, the 

 Antilles form, as we have seen, a highly peculiar region for the 

 opposite reason namely, that these islands, once united to Central 

 America, became detached at a remote period. This ancient sepa- 

 ration prevented the inroad of the higher and later forms of life, 

 whilst it would specialise and intensify the characters of the forms 

 which these islands originally claimed as their own. 



The case of other islands presents equally and in some cases 

 even more notable and characteristic examples of the influence of 

 isolation from or, conversely, of long-continued connection with con- 

 tinents upon the included life. Very interesting is it to note the 

 extreme differences which prevail between the islands of Bali and 

 Lombok in the Eastern Archipelago, each island being as large as 

 Corsica. They are separated by the Straits of Lombok, which are 

 about fifteen miles in width at their narrowest part. Despite the 

 narrowness of this channel which, however, bears evidence of its 

 antiquity in its great depth these islands differ far more widely in 



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