LVTZ, LIST OF GREATER ANTILLEAN SPIDERS 135 



their i^resent distribution is a measure of their success in extending their 

 range does not necessarily follow. It is altogether probable that spiders 

 fairly covered the earth in Oligocene times, and the few that were im- 

 prisoned in Baltic amber tell us nothing more than that they lived in that 

 region, among others, at that time. It is pleasing to note that Pocock 

 did not think it necessary to throw a bridge from continent to continent 

 on the shortest line (according to Mercator^s projection) between any two 

 portions of a present-day discontinuous range. He naturally found con- 

 siderable evidence of transfer in Arctic regions^^ and he also used, rather 

 freely, Antarctic connections between South America, Africa and Aus- 

 tralia. 



F. DahP^ has considered the distribution of spiders and concluded that 

 the Antarctic connection is improbable. Not all of his arguments seem 

 to be well founded. For example, one can not consistently uphold the 

 '^relict" idea and then combat the Antarctic connection on the ground 

 that so few relicts are found on the Antarctic islands. Most of the spi- 

 ders, for the explanation of whose distribution an Antarctic connection 

 might be desired, are tropical. It is therefore not surprising that re- 

 licts are not found on Antarctic islands. 



It is no more than ordinary common sense to favor the simplest ade- 

 quate explanation of a problem. It is unnecessary to review the volu- 

 minous literature concerning Antarctic connections between the three 

 southern continents. It is admitted that many facts favor such connec- 

 tions, especially the one betAveen South America and Australia, and that 

 nothing has been, or is likely to be, brought out Avhich will absolutely 

 disprove it. However, if a simpler explanation than the general eleva- 

 tion of more than 3,000 meters required to connect South America and 

 Australia, but which leaves Africa still to be accounted for, is adequate 

 it would seem to be preferable. The final court of appeals is, of course, 

 fossils, especially those in Antarctica, but even if numerous fossils are 

 found in Antarctica and they are seen to be similar to those found in the 

 southern portions of the other continents it will not prove actual con- 

 nections. It will merely show that there has been an interchange of 

 fauna — a thing not at all unknown between absolutely unconnected land 

 areas and a thing for which there was a vastly longer time than we 

 ordinarily have in mind since it requires a strong effort for us to bring 

 ourselves to thinking in terms of millions of years. 



^* The theory that practically all Tertiary migration was by v^ay of the Arctic regions 

 has been set forth most clearly by W. D. Matthew. It is amplified and convincingly dis- 

 cussed in his recent paper on "Climate and Evolution." Annals N. Y. Acad. Sci., Vol. 

 XXIV, pp. 171-318. 1915. 

 • " Zool. Anzeigrr. vol. XXXVII. pp. J70-282. 1011. 



