PREFACE. xvu 



That it was peopled by migration, or that wandering individuals in 

 search of new homes, finding the conditions adapted for their existence, 

 settled and colonized, and, in the case of birds, abandoned their migratory 

 habits, is refuted by the fact of the co-existence of peculiar and unique 

 forms, with others now found in regions widely separated from this 

 colony. Besides which, there are many species which, after making all 

 due allowance for all probable modes of migration at present in operation, 

 could scarcely have been transported thither under present conditions, 

 since either their physical characteristics, or the phenomena of their 

 present distribution, forbid such a supposition. 



It must be borne in mind that deserts such as those which isolate 

 Palestine on the south and east are found to present far more insuperable 

 barriers to the transport of species (excepting of course the case of desert 

 forms) than either seas or mountain ranges. E.g., it is the Sahara, and 

 not the Mediterranean, which separates the Ethiopian from the Patearctic 

 fauna. 



There remains, therefore, only the hypothesis of these species, and of 

 all other peculiar inhabitants of the basin, having arrived there by migra- 

 tion or general dispersion before the character of the surrounding region 

 presented the existing obstacles to their transport, and this at once 

 invites consideration of the geological problem. If their position be 

 mainly due to migration before the isolation of the area, it is necessary, 

 if possible, to ascertain two fixed points in time between which this 

 migration must have taken place. The migration must have been after 

 the close of the Eocene period. The palseontological character of the 

 most superficial deposits of all Southern Palestine is unquestionably 

 Eocene. There are no beds of fossils synchronizing with the Meiocene 

 deposits of Sicily, North Africa, and the Greek Islands. The whole of 

 Syria and Arabia Petrsea must have already emerged from the ocean, 

 while the greater part of the Mediterranean and its adjacent coasts and 

 islands was the bed of a Meiocene sea, and must have had a fauna and 

 flora contemporaneous with the Meiocene flora of Germany. We have 

 the clearest indications of this extension as far as Palestine. This Sir 

 J. D. Hooker has shown in tracing the glacial moraines which stud the 

 whole Lebanon range. There are also other indications of glacial action 

 which we may notice presently. 



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