362 C. SKOTTSBERG 



than trees of a more ordinary type, but this theory has been refuted [22^), and 

 recent observations in the field have not made me alter my opinion. 



Ab:se)ice of quadrupeds. The only mammals regarded as possibly native in 

 isolated islands are bats, but many islands do not have any. Storm-drift has been 

 postulated, but if the distance be very great, the animals might be without food 

 too long unless Nature provides a fair supply of air-born insects. To other land 

 mammals wide stretches o{ open water are an absolute obstacle and their absence 

 is regardeil as one of the safest proofs of the permanent isolation of oceanic is- 

 lands, just as the presence of endemic foxes in the Falkland Islands (now extinct) 

 supports the theory of an earlier connection with South America. 



However, we cannot know that indigenous mammals never existed on islands, 

 graduall}' having become extinct when the submergence of land had proceeded 

 and grazing grounds became smaller and smaller. It would appear that this theory 

 is contradicted b)' the fact that herbivorous mammals have been introduced by 

 man to many islands and do make a living there also when not tended, but if 

 allowed to naturalize and multi{)ly unrestrainedly in virgin surroundings, their 

 ravages would perhaps prove catastrophal to the native vegetation and, as a con- 

 secjuence thereof, to themselves. They would die out and leave the flora to re- 

 cover. We must remember that the islands are small, most of them very small, 

 that herbixorous animals need space and that pasture lands as they exist now 

 are a result of cleared forest soil and introduction of innumerable alien weeds or 

 cultigens. Another explanation of the absence of mammals is that the islands were 

 cut off so early that mammals had not yet taken possession of the earth or were 

 not universally distributed and perhaps not within reach. But these are mere wild 

 specuhitions. Xo fossil remains have been discovered, nor can they be expected 

 on purely volcanic islands. We cannot attack this problem with a hope of success 

 as long as we know little or nothing of the geograj)hical history of islands and 

 archi|)elagc)es. Hut wc have better remember that continental islands such as New 

 Zealand, New Caledonia, etc. are in the same precarious position with regard to 

 mammals as the Hawaiian Islands. 



-Xative reptiles and amphibians are also absent. CamI'BKIJ. (./^) mentions in 

 j)assing that tiicre arc half a dozen lizards in Hawaii, but all are species wide- 

 spread in the .South Pacific; most likely they were introduced with the early human 

 immigrants or j)erha])s later. That there are no frogs or toads would indicate, 

 Cami'I'.kij, thinks, that the archi])elago became isolated before the modern kinds 

 of these animals had been developed. lUit, as MlMFORD points out, many con- 

 tinental islands lack all lower vertebrates (/cV-,\ 24<S). 



1 low can we exj)lain all these i)eculiarities in oceanic islands.^ HooKKR's answer 

 was this: 



Thus, according to the hyi)()thc,sis of trans-oceanic nn'gration, and the theory of the 

 derivative orij^nn of spec ics, wc can mulcrstand why the ancient tyj)es . . . should have 

 survi\c(l on tlie islands to wliic h hut few of the superior race had j)enetrated ;• — we can 

 understand how it comes about, that so many continental species and genera are represented 

 on the island by similar hut not identical sj)ecies and genera, and that there is such 



