DERIVATION OF THE FLORA AND FAUNA 35I 



show the impossibihty of attributing any importance worth mentioning to long- 

 distance dispersal; the theory is, when it comes to migrations of floras, "not 

 worth a straw", and Rp:iCHE {20j), referring to the history of the Chilean flora, 

 called it "cine Kette von L'nwahrscheinlichkeiten". GOKDON {iij) was strongly 

 inclined do deny ist value and beliexed that plants, and more so plant associa- 

 tions, advance slowly over land and do not jump thousands of miles; he could 

 not, however, help paying some attention to "Nature's great Krakatau experi- 

 ment", of which enough has been said. 



Cain {^2) thinks that "migration is usually not a random matter" (p. 162) 

 and that long-distance dispersal rarely has resulted in migration and establishment, 

 nor does it ex[)lain the discontinuous areas. In reality he belongs to the trust- 

 worth}' opponents. One of the reasons adxanced b\' him is, however, not con- 

 clusive: 



The phenomenon of local races (subspecific endemics) is entirely op])Osed to the 

 idea of long-distance dispersal, for such variation depends upon isolation which would 

 not exist if long-distance dispersal were generally effective (p. 16 1). 



Those who are in favour of the theory emphasize the haphazard character 

 of the procedure; success may follow once and never more. If the immigrant 

 belongs to a polymorphous species, with intermediate forms between the sub- 

 species or varieties, it may, isolated as it remains from the rest of the population, 

 stand out as a separate insular taxon. 



Among the zoologists few, mainh- malacologists, are in favour of land con- 

 nections, but some entomologists agree with them. Berlaxd was already quoted. 

 As a rule a connection South America-Antarctica— Australia (or New Zealand) 

 is asked for, but to ExDERLElX this bridge was not sufficient: 



Die zahlreichen endemischen Gattangen (9) und Arten (2) zeigen, dass die Juan 

 Fernandez-Inseln ein Refugium fiir die Reste der Faunen unfangreicherer untergegan- 

 gener Gebiete darstellen, die nicht mit dem neotropischen Gebiet in Verbindung gestan- 

 den haben (Enderlein 6'^. 643). 



Did EXDERLEIX dream of a submerged Pacific continent.- ^Nlany of the island 

 flies are also native of the mainland of Chile, others have their relations there, 

 and if the islands were formerly connected with some other land, it was with 

 South America. Besides, the majority of Enderleix's new genera have been 

 reduced to synonymy by later authors, his speculations have little weight, and 

 W'VGODZIXSKV {2p^. 8i), referring to Giga7itodax kusc/ieli, arrived at a different 

 conclusion. Gigantodax is an exclusively South American genus. 



Chapter VII. 

 Biological characteristics of isolated islands. 



In his classical "Lecture on insular floras" [^138) J. D. HoOKER formulated, 

 in very lucid terms, the special features of island floras and his opinion on their 

 evolution. As examples he chose Macaronesia, St. Helena, Ascension and Ker- 

 guelen Island. Their peculiarities were stated under five items. 



