LUTZ, LIST OF GREATER ANTILLEAN SPIDERS 141 



gonia but are only poorly or not at all represented elsewhere. However, 

 is it necessary ? I think not. Even with ocean bottoms raised to form 

 connections where connections are wanted and present continents sunk 

 to explain the absence of forms where they are not fonnd, one mnst fur- 

 ther make all the assumptions required for the theory that distribution 

 has been accomplished by present-day land masses. Forms either origi- 

 nated in America and passed to the Old World by way of the Arctic or 

 the movement was in the reverse direction or, as is more probable, botli 

 are true. If geology demonstrates that there were land connections 

 there, the passage will be seen to have been easy. However, there is no 

 necessity for such connections since the distances are short and the time 

 was long. The more recent American forms probably originated, for 

 the most part, in America. The cutting off of the Arctic route by the 

 lowering of the temperature has temporarily, at least, prevented natural 

 interchange between the two hemispheres. Those recent forms which 

 originated in the north are adapted to temperate conditions (which in- 

 cludes more than mere ability to withstand cool winters) and they have 

 replaced in the north the old fauna which was adapted to more tropical 

 conditions. In the south there are numerous remnants of this old fauna 

 together with recent offshoots of it. The only assumptions necessary for 

 this theory are really statements of fact, namety, that the climate of the 

 Arctic was at least mild in the Tertiary and that many formerly wide 

 ranging forms are now restricted in their distribution. 



SUMMARY 



To summarize what seems to be the facts concerning AVest Indian spi- 

 ders: there has been considerable movement between the individual 

 islands and also betvv^een the mainland and the islands, especially at the 

 two ends of the island chain, even in recent times when the islands were 

 separate from each other and from the mainland. It is therefore unnec- 

 essary to suppose that such connections ever existed. Ancient forms 

 have had a longer time to reach the islands than the more recent ones, 

 they were adapted to a tropical environment, and the insular character 

 of the area has protected them, hence a large part of the fauna consists 

 of relicts as is shown by the relationships with South Africa, Madagascar, 

 Ceylon, Australia and the Philippines. Recent forms are now mingling 

 with and replacing the older forms. 



