DERIVATION OF THE FLORA AND FAUNA 355 



that those islands constitute the wrecks of either an ancient continent or an archipelago 

 which formerly extended further westwards ... (p. 15). 



Gulick's paper "Biological peculiarities of oceanic islands" does not, con- 

 trary to its title, contain a review of the special characteristics of island biota; 

 his object was to expound and defend the theory of permanent isolation of is- 

 lands like the Hawaiian, Galapagos, Juan Fernandez, St. Helena, etc., which are 

 said to offer irrefutable proofs of true oceanity. Of this enough has been said 

 already; I shall return to Hooker's five points, to which others may be added. 



Endemism. — The occurrence of numerous genera and species restricted to 

 oceanic islands has caused much discussion. "Reichtum an Endemismen ist iiber- 

 haupt der hervorragendste Charakterzug der Insel-Floren", Hayek wrote [304). It 

 is, however, equally pronounced in continental districts like the Cape region, south- 

 western Australia, western China, California or Chile, where local concentrations of 

 endemics are found. 



If insular endemics show distant affinity only or, in extreme cases, no af- 

 finity at all, to continental taxa, they are looked upon as relicts; as the islands 

 are geologically young, the endemics have not evolved there but must have im- 

 migrated from some mother country, where they have become extinct. They may, 

 however, have undergone some change after their arrival to the island. There 

 is also a possibility that the continental progenitor has, in its turn, changed in 

 a different direction, making its descendants so unlike that their relations are 

 obscured. Species only slightly different from continental ones are much more 

 numerous than the relicts; they are supposed to have originated in the islands 

 and give examples of so-called progressive endemism. As Ciiristensen {60. 149) 

 pointed out, another alternative leading to the establishment of endemic species 

 should be considered. On the continent, from where a plant found its way to 

 an isolated island, opportunities for crossing with other species often exist, 

 eventually leading to the disappearance of the original taxon with its special 

 characteristics. Its island offshoot does not share its fate but remains true to the 

 original type. The island form did not originate through a genetic change of 

 the continental species: it represents the surviving species and is, as it were, a relict. 

 This does not apply to the pteridophytes. Crosses are extremely rare, the fern 

 species represent, in a high degree, pure lines, whence it follows that insular en- 

 demics are much rarer than among the phanerogams. This is true, but it is 

 usually explained as a result of the enormous spore production and the facility 

 with which they spread. 



Opinions about the true nature of systematically isolated taxa vary. GUPPY 

 {122) regarded them as either highly specialized products of the islands, "the first 

 of their race", or modified forms of allied continental genera, the majority of which 

 had passed away, "the last of their race" and probably doomed; to him the 

 islands appealed "more as registers of past floral conditions in the continents 

 than as representing their present state" — this in accordance with Hooker's 

 views. The Age-and-area theory of WiLLlS [286) claims that wides are older 

 than endemics, a rule with few exceptions; in another paper [283) he states that 

 "insular endemic genera are as a rule young beginners, not relics". I have dis- 



