324 



C. SKOTTSBERG 



Evidence with regard to the nature and distribution of land snails is of the utmost 

 importance, for it is from the nature of the land-snail fauna in Polynesia that Mr. Pilsbry 

 has reached the conclusion that the whole of Polynesia, with Hawaii, was once a great 

 continental land mass. Partula — an ancient generalized type of land snail — is wide- 

 spread in Polynesia and Melanesia and not elsewhere ; whereas many groups (e.g. He- 

 licidae and Arionidae) found widely spread in the world are absent in Polynesia, etc. 

 Professor Buxton is of the opinion that Pilsbry has been more successful than any other 

 writer in establishing a case for the early existence of a mid-Pacific continent. 



But how early or how late.- To explain the absence of modern land molluscs 

 we may have to go back to late Tertiary times only, and we should need other 

 proofs of a distribution of land and sea sufficiently dififerent from the present one; 

 perhaps they will be found. But we cannot simply fill out the Pacific basin with 

 land and leave the surrounding continents unaltered. Often enough due regard 

 was not taken to such circumstances. SwEZEV [262), who for his own part believed 

 that the entire insect fauna of Hawaii owed its presence to accidental migration, 

 quotes two of the authors of "Fauna Hawaiiensis" who did, in his opinion with- 

 out any reason, build bridges where they found that they needed them, Mevrick 

 and Lord Walsingham. Meyrick, an authority on Microlepidoptera, when stating 

 that among the endemic Hawaiian genera three were of south Pacific affinity, pos- 

 tulated "the former existence of a considerable land area (now submerged) be- 

 tween Xew Zealand and South America", a land mass which compares to Arldt's 

 South Pacific bridge — such a land still exists and is not submerged : Antarctica! 

 — and he also believed in a "Palaeonesia" extending from Rapa to Hawaii and 

 from Pitcairn Island to the Society and Cook groups. Little room is left for the 

 water of the ocean, but he does not argue that these land masses were contem- 

 poraneous. Lord Walsingham who based his opinion on the distribution and 

 relationships of the Microlepidoptera regarded the Hawaiian Islands as representing 

 the summits of mountain ranges formerly belonging to a continent, "a lost Paci- 

 fica"; if not accepted, "some other theory possibly even less acceptable must be 

 devised" — equally beyond the possibility of exact proof. 



It is easy to understand that, in all these discussions and speculations, Hawaii 

 in its isolated position and with its rich flora and fauna should be the object of 

 the main interest, and I shall end this chapter with a review of E. H. Bryan's recent 

 contribution, "The Hawaiian Chain" (^o), equally instructive as popularly written. 

 Bryan believes in a continental Melanesia but regards Haw-aii as oceanic, but 

 this does not prevent him from accepting the Leeward islands as remnant of a 

 long, deeply submerged ridge, nor from admitting that the Hawaiian Islands proper 

 may have been greater and, in part at least, united. The chain is supposed to 

 have emerged first at its extreme western end, where we now only find the rem- 

 nants of once larger islands; it appeared some time during Tertiary, the forma- 

 tion proceeding toward the east, with the island of Hawaii, where ejection of 

 lava still occurs, as the youngest link, the chain having been completed by the 

 end of the Pliocene. Bryan, who has a wide knowledge of the Hawaiian fauna, is 

 no friend of land bridges and less so of submerged continental masses, but un- 

 like many other zoologists he admits that it is very difficult to explain the fauna 



