carbonaceous material in a more or less fragmentary condition, but sufficiently continuous to enable the existence of three layers to be determined: an outer and inner, which are very thin, separated by a space, now filled with calcite, from a thicker middle layer, which measures from 0.005 to 0.01 mm. across. The middle layer sometimes breaks up into threads, and the superficial films have_a reticular appearance, which may, however, be due to post-mortem changes. In the region of the virgula and also along the free edges of the thecæ the wall thickens, partly by an enlargement of the space between the layers, and partly by a thickening of the middle layer. Thus, in one example the total thickness of the wall in the virgular region is 0·075 mm., and of the virgula itself, which represents the middle layer, 0.037 mm.; similarly at the margin of the theca the total thickness was found to be 0.085 mm., the included middle layer measuring 0.045 mm. Thin threads of carbonaceous material extend from the middle to the superficial layers, and are particularly obvious in the thickened regions. The virgula would appear to possess no independent existence; it seems to be merely a thickening of the middle layer. 5. Report on the Circulation of Underground Water. [Maps, specimens, and photographs of geological interest were exhibited each day in the Temporary Museum from 10 A.M. to 6 P.M.] SECTION D.-BIOLOGY. PRESIDENT OF THE SECTION-Rev. H. B. TRISTRAM, M.A., LL.D., D.D., F.R.S. THURSDAY, SEPTEMBER 14. [For the President's Address see p. 784.] The following Reports and Papers were read : 1. Report on the Zoology of the Sandwich Islands.-See Reports, p. 523. 2. On the Zoology of the Sandwich Islands. By D. SHARP, F.R.S. The islands were formerly supposed to be rich in plant and comparatively poor in animal life. But the progress of knowledge is modifying this latter view. In 1880 Wallace in Island Life' furnished the following statistics as to this archipelago viz.: birds, 43 species, 24 of them peculiar to the islands; land and freshwater mollusca, 300 or 400 species, all peculiar; insects, scarcely anything known; plants, 689 species, 377 peculiar. After one year's investigation by the committees of the British Association and of the Royal Society, and incorporating the recent results of the work of private naturalists, the figures are: birds, 78 species, 57 of them peculiar; land and freshwater mollusca, 475 species, all peculiar; insects, 1,000 species, 700 of them peculiar ; plants (according to Hillebrand), 999 species, 653 peculiar (many of those not peculiar being introduced by man). But the investigations of the committees show that these results are very incomplete, at any rate in the case of the insects, which cannot be estimated at less than 3,000 species, 2,500 or 2,600 of the number being peculiar. These numbers in the case of the fauna are less than those of approximately similar areas in less insular parts. Devonshire has 84 resident species of birds and 30 summer migrants. The insects amount to about 6,000 species, and the land and fresh-water mollusca to 97 species, the vascular plants being about the same in number as those of the Sandwich Islands. But there has already been very great extinction in this latter area, much of it probably even before the discovery and appropriation of the islands by civilised man. The working of the British Association and of the Royal Society committees seems to offer the only chance of investigating the fauna. The native creatures are extremely difficult to find, and the usual inducements to sportsmen and collectors are wanting; while the small population and the absence of great centres of intellectual activity in the islands render it very improbable that the work will be accomplished by residents in the archipelago, though these might give very valuable assistance. 3. Interim Report on a Digest of Observations on the Migration of Birds at Lighthouses.-See Reports, p. 524. 4. Report on the Zoology and Botany of the West India Islands. 5. Note on the Discovery of Diprotodon Remains in Australia. 6. The following Address, by Rev. H. B. TRISTRAM, F.R.S., President of the Section, who was not able to attend the Meeting, was read by Sir W. H. FLOWER, K.C.B., F.R.S. Address:- It is difficult for the mind to grasp the advance in biological science (I use the term biology in its wide etymological, not its recently restricted sense) which has taken place since I first attended the meetings of the British Association, some forty years ago. In those days, the now familiar expressions of natural selection,' isolation,' the struggle for existence,'' the survival of the fittest,' were unheard of and unknown, though many an observer was busied in culling the facts which were being poured into the lap of the philosopher who should mould the first great epoch in natural science since the days of Linnæus. It is to the importance and value of field observation that I would venture in the first place to direct your attention. My predecessors in this chair have been, of recent years, distinguished men who have searched deeply into the abstrusest mysteries of physiology. Thither I do not presume to follow them. I rather come before you as a survivor of the oldworld naturalist, as one whose researches have been, not in the laboratory or with the microscope, but on the wide desert, the mountain side, and the isles of the sea. This year is the centenary of the death of Gilbert White, whom we may look upon as the father of field naturalists. It is true that Sir T. Browne, Willughby, and Ray had each, in the middle of the seventeenth century, committed various observations to print; but though Willughby, at least, recognised the importance of the soft parts as well as the osteology, in affording a key to classification, as may be seen from his observation of the peculiar formation, in the Divers (Colymbida) of the tibia, with its prolonged procnemial process, of which he has given a figure, or his description of the elongation of the posterior branches of the woodpecker's tongue, as well as by his careful description of the intestines of all specimens which came under his notice in the flesh, none of these systematically noted the habits of birds, apart from an occasional mention of their nidification, and very rarely do they even describe the eggs. But White was the first observer to recognise how much may be learnt from the life habits of birds. He is generally content with recording his observations, leaving to others to speculate. Fond of Virgilian quotations (he was a fellow of Oriel of the last century), his quotations are often made with a view to prove the scrupulous accuracy of the Roman poet, as tested by his (White's) own observations. In an age, incredulous as to that which appears to break the uniformity of nature, but quick to recognise all the phenomena of life, a contrast arises before the mind's eye between the abiding strength of the objective method, which brings Gilbert White in touch with the great writers whose works are for all time, and the transient feebleness of the modern introspective philosophies, vexed with the problems of psychology. The modern psychologist propounds his theory of man and the universe, and we read him, and go on our way, and straightway forget. Herodotus and Thucydides tell a plain tale in plain language, or the Curate of Selborne shows us the hawk on the wing, or the snake in the grass, as he saw them day by day, and, somehow, the simple story lives and moves him who reads it long after the subtleties of this or that philosophical theory have had their day and passed into the limbo of oblivion. But, invaluable as has been the example of Gilbert White in teaching us how to observe, his field was a very narrow one, circumscribed for the most part by the boundaries of a single parish, and on the subject of geographical distribution (as we know it now) he could contribute nothing, a subject on which even the best explorers of that day were strangely inobservant and inexact. A century and a half ago, it had not come to be recognised that distribution is (along, of course, with morphology and physiology), a most important factor in determining the facts of biology. It is difficult to estimate what might have been gained in the case of many species, now irreparably lost, had Forster and the other companions of Captain Cook, to say nothing of many previous voyagers, had the slightest conception of the importance of noting the exact locality of each specimen they collected. They seem scarcely to have recognised the specific distinctions of the characteristic genera of the Pacific Islands at all, or, if they did, to have dismissed them with the remark, 'On this island was found a flycatcher, a pigeon, or a parrot similar to those found in New Holland, but with white tail-feathers instead of black, an orange instead of a scarlet breast, or red shoulders instead of yellow.' As we turn over the pages of Latham or Shaw, how often do we find for locality' one of the islands of the South Sea,' and, even where the locality is given, subsequent research has proved it erroneous, as though the specimens had been subsequently ticketed; as Le Vaillant described many of his South African birds from memory. Thus Latham, after describing very accurately Rhipidura flabellifera, from the south island of New Zealand, remarks, apparently on Forster's authority, that it is subject to variation; that in the island of Tanna another was met with, with a different tail, &c., and that there was another variety in the collection of Sir Joseph Banks. Endless perplexity has been caused by the Psittacus pygmæus of Gmelin (of which Latham's type is at Vienna) being stated in the inventory as from Botany Bay, by Latham from Otaheite, and in his book as inhabiting several of the islands of the South Seas, and now it proves to be the female Psittacus palmarum from the New Hebrides. These are but samples of the confusion caused by the inaccuracies of the old voyagers. Had there been in the first crew who landed on the Island of Bourbon, I will not say a naturalist, but even a simple-hearted Leguat, to tell the artless tale of what he saw, or had there been among the Portuguese discoverers of Mauritius one who could note and describe the habits of its birds with the accuracy with which a Poulton could record the ways and doings of our Lepidoptera, how vastly would our knowledge of a perished fauna have been enriched! It is only since we learned from Darwin and Wallace the power of isolation in the differentiation of species that special attention has been paid to the peculiarities of insular forms. Here the field naturalist comes in as the helpful servant of the philosopher and the systematist by illustrating the operation of isolation in the differentiation of species. I may take the typical examples of two groups of oceanic islands, differing as widely as possible in their position on the globe-the Sandwich Islands in the centre of the Pacific, thousands of miles from the nearest continent, and the Canaries, within sight of the African coast--but agreeing in this, that both are truly oceanic groups, of purely volcanic origin, the ocean depths close to the Canaries, and between the different islands, varying from 1,500 to 2,000 fathoms. In the one we may study the expiring relics of an avifauna completely differentiated by isolation; in the other we have the opportunity of tracing the incipient stages of the same process. The Sandwich Islands have long been known as possessing an avifauna not surpasse interesting peculiarity by that of New Zealand or Madagascar; in fact, it see is though their vast distance from the continent had intensified the influences of .solation. There is scarcely a passerine bird in its indigenous fauna which can be referred to any genus known elsewhere. But, until the very recent 1893. 3 E researches of Mr. Scott Wilson, and the explorations of the Honourable W. Rothschild's collectors, it was not known that almost every island of the group possessed one or more representatives of each of these peculiar genera. Thus, every island which has been thoroughly explored, and in which any extent of the primeval forest remains, possesses, or has possessed, its own peculiar species of Hemignathus, Himatione, Phaornis, Acrulocercus, Loxops, Drepanis, as well as of the massivebeaked finches, which emulate the Geospiza of the Galapagos. Professor Newton has shown that while the greater number of these are, probably, of American origin, yet the South Pacific has contributed its quota to this museum of ornithological rarities, which Mr. Clarke very justly proposes to make a distinct biological sub-region. That each of the islands of this group, however small, should possess a flora specifically distinct suggests thoughts of the vast periods occupied in their differentiation. In the Canary Islands, either because they are geologically more recent, or because of their proximity to the African coast, which has facilitated frequent immigrations from the continent, the process of differentiation is only partially accomplished. Yet there is scarcely a resident species which is not more or less modified, and this modification is yet further advanced in the westernmost islands than in those nearest to Africa. În Fuertaventura and Lanzarote, waterless and treeless, there is little change, and the fauna is almost identical with that of the neighbouring Sahara. There is a whin-chat, Pratincola dacotiæ, discovered by my companion, Mr. Meade-Waldo, peculiar to Fuertaventura, which may possibly be found on the opposite coast, though it has not yet been met with by any collectors there. Now, our whin-chat is a common winter visitant all down the West African coast, and it seems probable that isolation has produced the very marked characters of the Canarian form, while the continental individuals have been restrained from variation by their frequent association with their migratory relations. A similar cause may explain why the blackbird, an extremely common resident in all the Canary Islands, has not been modified in the least, since many migratory individuals of the same species sojourn every winter in the islands. Or take the blue titmouse. Our familiar resident is replaced along the coast of North Africa by a representative species, Parus ultramarinus, differentiated chiefly by a black instead of a blue cap, and a slate-coloured instead of a green back. The titmouse of Lanzarote and Fuertaventura is barely separable from that of Algeria, but is much smaller and paler, probably owing to scarcity of food and a dry desert climate Passing, 100 miles further to sea, to Grand Canary, we find in the woods and forests a bird in all respects similar to the Algerian in colour and dimensions, with one exception the greater wing coverts of the Algerian are tipped with white, forming a broad bar when the wing is closed. This, present in the Fuertaventura form, is represented in the Canarian by the faintest white tips, and in the birds from the next islands, Tenerife and Gomera, this is altogether absent. This form has been recognised as Parus tenerifæ. Proceeding to the north-west outermost island, Palma, we find a very distinct species, with different proportions, a longer tail, and white abdomen instead of yellow. In the Ultima Thule, Hierro, we find a second very distinct species, resembling that of Tenerife in the absence of the wing bar and in all other respects, except that the back is green like the European, instead of slate as in all the other species. Thus we find in this group a uniform graduation of variation as we proceed further from the cradle of the race. A similar series of modifications may be traced in the chaffinch (Fringilla), which has been in like manner derived from the North African F. spodiogena, and in which the extreme variation is to be found in the westernmost islands of Palma and Hierro. The willow wren (Phylloscopus trochilus), extremely numerous and resident, has entirely changed its habits, though not its plumage, and I have felt justified in distinguishing it as Ph. fortunatus. In note and habits it is entirely different from our bird, and though it builds a domed nest it is always near the top of lofty trees, most frequently in palm-trees. The only external difference from our bird consists in its paler tarsi and more rounded wing, so that its power of flight is weaker, but, were it not for the marked difference in its habits and voice, |