372 



C. SKOTTSBERG 



done to examine the genotypical constitution of this astonishing assemblage of 

 local forms; some may, for all we know, be ecotypes, but experimental studies 

 have not been made. A limited number of hybrids have been described, but we 

 know nothing of their behaviour. Anyhow, the floristic dift'erence between the islands 

 is very striking and hardly in favour of the theory of transoceanic migration, for 

 the majority of organisms seem to have been unable to cross even the straits 

 separating the islands, and biotic factors preventing establishment can hardly be 

 made responsible in so many cases. 



Chapter IX. 

 Juan Fernandez — oceanic or continental ? 



To \\'.\LLACE as well as to the majority of biogeographers the Juan Fer- 

 nandez Islands were typically oceanic in spite of their moderate distance from 

 South America. They had the advantage of antiquity. Wallace remarks, for 

 the means of transmission had formerly been greater than now, their surface was 

 varied, soil and climate favourable, "offering many chances for the preservation 

 and increase of whatever plants and animals had chanced to reach them" (p. 287). 

 Had the character of Masafuera been known to him he might have been less 

 optimistic. The land-shell fauna, entirely endemic, testified to the great age of 

 the islands, for none had been introduced for so long a period that all which 

 did come had given rise to new forms — or were the last of a fauna extinct 

 on the continent. 



JOHOW [ijo] based his opinion on Wallace; when discussing the dispersal 

 agencies and the morphology of the diaspores his starting-point was ^wo islands, 

 Masatierra plus Santa Clara and Masafuera, which has risen separately from the 

 deep sea. It is strange that he never thought of another possibilit)', because the 

 geologist who went with him and who wrote a chapter on the geology of Masa- 

 tierra, claimed to have discovered, in one place, a fundament of rocks older than 

 the omnipresent young basalt — ^JOHOW could not know that the interpretation 

 of this stratum was false, as later shown by QCEN'SEL {302). After his visit to 

 the Desventuradas JOHOW modified his opinion; the submarine ridge uniting these 

 little islands with Juan Fernandez had then been discovered: 



Die unter gleicher Breite mit dem Hafen Caldera und in derselben Entfernung 

 vom Kontinent wie Juan Fernandez gelegene Inselgruppe ist vulkanischen Ursprungs 

 und stellt, wie die von dem Mitglied der Expedition, Herrn Chaigneau, ausgeliihrten 

 Lotungen ergaben, die iiber Wasser befindlichen hochsten Gipfel einer im tJbrigen 

 unterseeisch verlaufenden Bergkette dar, welcher auch die Inseln der Juan-Femandez- 

 Gruppe als siidlichste Gipfel angehoren. Aus dem Vergleiche der Floren und Faunen 

 beider Archipele, vvelche trotz der grossen klimatischen Verschiedenheiten frappante 

 Vervvandtschaft aufweisen, ergiebt sich mit zwingender Xotwendigkeit die Hypothese, 

 dass die zwei Inselgruppen in der Vorzeit mit einander in Landverbindung gestanden 

 haben und dass ihre Isolierung die Folge einer stattgehabten Senkung jener Bergkette 

 ist [jso. 259). 



