756 BIRDS [DISTRIBUTION. of the Mediterranean Subregion, offer some peculiarities too remarkable to be here left unnoticed. First we have the Azores, the subject of an excellent monograph by Mi- Frederick Godman, 1 in which is contained the result of his own investigations in that group, as well as those of his predecessors. There is a general tendency among Azorean Birds to vary more or less from their continental repre sentatives, and this is especially shown by the former having always darker plumage and stronger bills and legs. In one instance the variation is so excessive that it fully justifies the establishment of a specific distinction. This is the case of the Bullfinch of the more eastern of these islands (Pyrrhula murina], the male of which, instead of the ruddy breast of its well-known congener (P. vulgaris), has that part of a sober mouse-colour. A similar sombre hue dis tinguishes the peculiar Chaffinch of the Canary Islands (Fr ing ilia teydea), but to these islands as well as the Azores and Madeiras there belongs in common another Chaffinch (F. tintulon], which, though very nearly allied to that of Mauritania (F. spodiogenia), is perfectly recogniz able, and not found elsewhere. Madeira has also its peculiar Golden-crested Wren (Regulus maderensis), and its peculiar Pigeon (Columba trocaz), while two allied forms of the latter (C. laurivora and C. bollii) are found only in the Canaries. Further on this subject we must not go ; we can only state that Mr Godman has shown good reason for declaring that the avifauna of all these islands is the effect of colonization extending over a long period of years, and going on now. The Mongolian has the largest number of peculiar genera of any Palsearctic Subregion. In Sylviidce there is 1, in Timeliid X 2, in Panuridas and Ixidae 1 each, in Fringil- lidce 3, in Sturnidce and Pterocleidce 2 1 respectively, in Pkasianidce 2, and in Anatidce 1 or 13 in all ; but, in com mon with the Indian Region, and that only, there are 10 of Sylviidce, of Timeliidce, 1 of Troglodytidce, 3 oiLiotrichidce, 1, rather doubtful in position, but possibly belonging to Panuridce, 1 of Ixidce, 4 of Muscicapidce, 1 of Motacillidce arid Fringillidce respectively, 2 of Sturnidce, 1 of Picidce, 2 of Strigidce and as many of Columbidce, 1 of Tetraonidos, 4 of Phasianidce, and 1 generally referred to Scolopacidce* or 39 altogether. In common with the Ethiopian Region alone, the Mongolian Subregion has only 1 genus, and that belongs to Motacillidce ; but in common with both Ethiopian and Indian, though with these only, there are 1 of Muscicapidce and 1 of Laniidce; while 2 genera 1 of Fringillidce and 1 of Scolopacidae belong equally to the Nearctic fauna : 2 genera, members respectively of the Dicceidce and Pittidce, are common as well to the Ethiopian, Indian, and Australian Regions. The Siberian Subregion seems to have but 1 genus peculiar. This is Eurynorhynchus, one of the Scolopacidae; but as its breeding-quarters have never yet been discovered the matter must remain in doubt. One genus of Laridce and 6 of Alcidce are also common to the Nearctic Region, but do not inhabit any other Palsearctic Subregion. It would extend the present article far beyond all reasonable bounds were we to dwell upon more than a few of the curiosities of distribution which have been revealed by the continuous observations of European ornithologists. There is no need to travel out of our own island to meet with some of the most remarkable among them, and we may take that of the Nightingale (Daulias luscinia) as an 1 Natural History of the Azores or Western Islands, 8vo. London : 1870. 2 The genus of this family here meant is Syrrhaptes, the Three-toed Sand-Grouse, one species of which (S. paradoxus) overran Europe in astounding numbers in 1863, and effected a temporary settlement both in Denmark and Holland. 3 This is Ibidorhynchus, which, until some details of its osteology tie known, can hardly be placed without risk of error. example. In England the western limit of the range of Dist this incomparable songster seems to be formed by the tio valley of the Exe, which is only overstepped on rare *% occasions Montagu having once heard it near Kingsbridge, ga while it is said to have been observed at Teignmouth and Barnstaple. But even in the east of Devonshire it is local and rare, as it also is in the north of Somersetshire, though plentiful in other parts of that county. Crossing the Bristol Channel it is said to be not uncommon at times near Cowbridge in Glamorganshire ; but this seems to be an isolated spot, or at any rate there is no evidence of its being found elsewhere in Wales, or between that place and Tintern on the Wye, where it has been reported to be plentiful. Thence there is more or less good testimony of its occurrence in Herefordshire, Shropshire, Staffordshire, Derbyshire, and so on, to about 5 miles north of York, but not further. Along the line thus sketched out and imme diately to the east and south of it, the appearance of the nightingale, even if regular, which may be doubted, is rare, and the bird exceedingly local ; but in many parts of the midland, eastern, and southern counties it is abundant, and the woods, coppices, and gardens ring with that thrill ing song which has been the theme of writers in all ages. There are many assertions of its occurrence in England further to the northward, but some of them rest on anony mous authority only, and all must be regarded with the greatest suspicion. Still more open to doubt are the state ments which have been made as to its visits to Scotland, while in Ireland there is no pretence even of its appearance. No reasonable mode of accounting for the partial distribu tion of the Nightingale has hitherto been propounded : there is no peculiar kind of soil which it especially affects, or none, so far as we know, that it especially avoids ; and the same may be said of its relations to the flora of this country. It is not so entirely adscriptus glebce that it will not readily betake itself to new localities suited to it.s wants, when these have been formed within its natural limits, though they may be miles away from its ancient haunts. On the contrary, it is often one of the first birds to establish itself when a heath has been broken up, and plantations of trees thereon made have grown sufficiently to afford it the sheltering covert that it loves. This instance, taken from a bird whose habits have been so closely studied both in captivity and at large, and one which is so familiar, and in many places so numerous, that abundant opportunities are given for observing all that can be observed about it, shews how futile would be the expecta tion that in most cases we could at present, even if ever, satisfactorily account for the existing causes which limit the distribution of species. A vast majority of them, we know, have each its bounds, which virtually it cannot pass, and the case of the Nightingale in England, beyond the fact that its distribution is extremely well marked, and therefore has long attracted especial attention, has really nothing out of the common way in it. 4 In Europe, the neighbourhood of Copenhagen is the most northern point which our Nightingale is asserted to reach; but on the continent its range is less extended, and though abundant in Mecklenburg, it is not found in that part of Pomerania 4 When the history of the earth shall be really well and minutely understood, it seems quite possible that as much light will be shed on this and other particular cases of the same kind by a knowledge of the various changes and displacements which sea and land have undergone as has already been done by the same means in regard to many of the general facts of distribution. The results of the labour of the geologist are doubtless just as necessary to, and closely connected with, the work of the biologist, as those of the investigation of the historian are to and with the efficiency of the statesman ; while, in return, the researches of the biologist are, or ought to be, of the greatest service to the geologist. The history of the earth is for a lor.g period of time that
of its inhabitants.