DKRIVATION OF THK FLORA AND FAUNA 365 



entwickelung alter, vielleicht den ("harakter einer iilteren tertiiiren Periode rei)rasentieren- 

 dcr Stammrtoren stattgefunden hat, welche sich hier im Schiitze der Abgeschiedcnheit 

 fern von dem EintUiss kontinentaler llmwiilzungscrscheinungen si( h erhalten konnten 

 {joj. 12S). 



Dridk agreed with IIooKl'.K tliat extinct species, known as fossils in luirope, 

 were the ancestors of s|)ecies now endemic in Macaronesia. 



With regard to the Pacific islands several authors have discussed the ([uestion 

 to what extent endeiuisni has been of a progressive kind and if not only s[)ecies but 

 also isolated genera have evolved on the islands from a limited number of un- 

 known ancestors. Most of them, in spite of their firm belief that the islands are, geologi- 

 cally spoken, very recent, regard the insular biota as a local product; the first arrivals 

 had had time to give rise to new genera, those that came a little later became 

 new species, still more recent ones varieties of a continental species, and such as 

 arrived in our era have not had time to change but are expected to do so, because 

 isolation in a new and strange environment makes them adapt themselves by changing 

 their genetic structure. 1 l.WKK [jo^. 252) expressed this very clearly: 



Dass diese eingewanderten Elemente infolge ihrer Isolierung eigene Entwickelungs- 

 richtungen einschlugen, die sich in einer oft auftallend grossen Zahl von Endemismen 

 aussern, ist ja selbstverstiindlich. 



Among botanists of the latest decennia Andrews [6) may be chosen as a 

 representative of the school of "rapid adaptive radiation". 



If a newcomer belongs to a primary form of a virile genus such as Acacia, CopJ-os»ia, 

 etc. it may be expected rapidly to become differentiated into varieties and species. As 

 Bentham pointed out long ago, the geographic station of a waif or colonist imposes 

 variations upon it almost from the moment of its arrival. Eucalypts planted in New 

 Zealand, California, and other places present marked differences from the forms the same 

 species possess in Australia. In the second place, if the plant assemblage into which 

 the waif or colonist arrives be a result of long-continued struggle for existence such 

 as occurs commonly in Holarctica and the cosmopolitan tropics, then the opportunity 

 for the development of new forms is remote, unless the new arrival itself is a plastic 

 form, and a grand example of the survival of the fittest. If, on the other hand, the 

 newcomer belongs to an agressive species in its own continental setting, then it has, 

 all other things being equal, an excellent chance of survival and of differentiating into 

 new forms (p. 617). 



Andrews, himself an Australian, speaking on the Hawaiian flora, mentioned 

 Acacia, Coprosuia and other genera of Australian or southwest Pacific origin which 

 developed new, endemic forms in Hawaii, where they take a prominent part in the 

 vegetation. But when it comes to Eucalypts planted in California, nobody will, I 

 suppose, consider this example as a proof of the origin of new taxa under the 

 influence of new surroundings. 



There is, he continues, a difference in the physical character of islands; some 

 did not encourage the colonist to vary and evolve, others did. 



If the island ... be very small and of negligible relief, it again has but little op- 

 portunity for differentiation, and, furthermore, if the island l)e even large and high, but 

 the time be short . . . the response will have been but slight (I.e.). 



