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Show 450 ISLAND LIFE. (PART II, species, could have reached the places where they ar~ now found ; and this gives us an idea of th~ complete senes of chano-es throuo-h which New Zealand is believed to have passed 0 b 1 . f . in order to brino- about its abnormally dense popu atwn ° wmg-less birds. Fir:t, we must suppose a land conn~ction with some country inhabited by struthious birds, from ';hic~ the ancestral forms mio-ht be derived· secondly, a separatiOn mto many considerable 0 islands in whi~h the various distinct species might become differentiated; thirdly, an elevatio~ bringin~ ab~ut the union of these islands to unite the distmct species m one area; and fourthly, a subsidence of a large part ?f the area, leaving the present islands with the various specws crowded together. If New Zealand has really gone through such a series of changes as here suggested, some proofs of it might perhaps be obtained in the outlying islands which were once, presumably, joined with it. And this gives great importance to the st atement of the aboriginefl of the Chatham Islands, that the Apteryx formerly lived there but was exterminated about 183:5. It is to be hoped that some search will be made here and also in Norfolk Island, in both of which it is not improbable remains either of Apteryx or Dinornis might be discovered. So far we find nothing to object to in the speculations of Captain Hutton, with which, on the contrary, we almost wholly concur; but we cannot follow him when he goes on to suggest an Antarctic continent uniting New Zealand and Australia with South America, and probably also with South Africa, in ord~r to explain the .existing distribution of struthious birds. Our best anatomists, as we have seen, agree that both Dinornis and Apteryx are more nearly allied to the cassowaries and emus than to the ostriches and rheas ; and we see that the form of the sea-bottom suggests a former connection with North Australia and New Guinea-the very region where these types most abound, and where in all probability they originated. Tho suggestion that all the struthious birds of the world sprang from a common ancestor at no very remote period, and that their existing distribution is d.ue to direct land communication between the countries they now inhabit, is one utterly opposed CllAP. XXI.] NEW ZEALAND. 451 t~ al~ so~nd princip~es of reasoning in questions of geographical dis~nbutwn. For It depends upon two assumptions, both of whiCh are at least doubtful, if not certainly false-the first, that their distribution over the globe has never in past ao-es been very different from what it is now ; and the second, that tho ancestral forms of these birds never had the power of flight. As to the first assumption, we have found in almost every case t?at ~ro~ps now. scattered over two or more continents formerly hved m mtervemng areas of existing land. Thus the marsupials o.f So~th America and Australia are connected by forms which hvod m North America and Europe; the camels of Asia and the llamas of the Andes had many extinct common ancestors m North America; the lemurs of Africa and Asia had their ancestors in Europe, as did the troo-ons of South America Mn'c a, .and tropical Asia. But besideso this general evidence we' ?avo dir~ct proof that the struthious birds had a wider range m past tunes than now. Remains of extinct rheas have been found in Central Brazil, and those of ostriches in North India · while remains, believed to be of struthious birds, are found i~ the Eocene deposits of England ; and the Cretaceous rocks of North America have yielded the extraordinary toothed bird, Hesperornis, which Professor 0. Marsh declares to have been "a carnivorous swimming ostrich." As to the second point, we have the remarkable fact that all known birds of this group have not only the rudiments of wingbones, but also the rudiments of wings, that, is, an external limb bearing rigid quills or largely-developed plumes. In the cassowary these wing-feathers are reduced to long spines like porcupine-quills, while even in: the Apteryx, the minute external wing ~ears a series of nearly twenty stiff quill-like feathers. 1 These facts render it probable that the struthious birds do not owe their imperfect wings to a direct evolution from a reptilian type, but to a retrograde development from some low form of winged birds, analogous to that which has produced the dodo and the solitaire from the more highly-developed pigeon-type. Professor Marsh bas proved, that so far back as 1 See flg. in Tmng. of N. Z. Institute) VoJ. HI., plate 12b, fig. 2. G G 2 |
